United States
             Environmental Protection
              Environmental Sciences Research
              Research Triangle Park NC 277 11
EPA-600, 9-79-041
November 1 979
              Research and Development
Workshop on
Models in
Complex Terrain


Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology  Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are-
      1.  Environmental Health  Effects Research
      2  Environmental Protection Technology
      3  Ecological Research
      4  Environmental Monitoring
      5.  Socioeconomic Environmental Studies
      6  Scientific and Technical Assessment Reports (STAR)
      7  Interagency Energy-Environment Research and Development
      8.  "Special" Reports
      9.  Miscellaneous Reports
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.

                                           November 1979

               Einar L. Hovind
              Max W. Edelstein
           Victoria C. Sutherland

     North American Weather Consultants
          Goleta, California  93017
                Contract No.
               Project Officer

             George C. Holzworth
     Meteorology and Assessment Division
 Environmental Sciences Research Laboratory
Research Triangle Park, North Carolina  27711


     This report has been reviewed by  the  Environmental Sciences
Research Laboratory, U. S. Environmental  Protection  Agency,  and
approved for publication.  Approval does not  signify that the contents
neccessarily reflect the views  and policies  of  the U. S.  Environmental
Protection Agency, nor  does mention  of trade names  or commercial
products constitute endorsement or recommendation for use.


     During the period July 16-20,  1979, an EPA sponsored Workshop was
conducted in Raleigh, North  Carolina, to address problems associated
with plume dispersion modeling  in complex terrain.  Similar topics
have been the  subject of  other  workshops sponsored during the past
three years,  such as  the 1977 AMS Workshop on Stability Classification
Schemes and Sigma Curves; the 1977 Specialists'  Conference on the EPA
Modeling Guideline;  and  the  1976  Albuquerque Workshop on Research
Needs for Atmospheric Transport and Diffusion in Complex Terrain.

     Since the Albuquerque Workshop the Clean Air  Act Amendments of
1977 were signed  into law.   These amendments have placed  a heavy
burden upon regulatory agencies and industry in that they call for
regulations which specify the use  of  dispersion models to achieve air
quality limits pertinent  to  prevention  of significant deterioration
and attainment of National Air Quality Standards.  The  problem
is particularly  critical  regarding dispersion in complex  terrain
since EPA, so  far,  has  not  specified  models  with demonstrated
high degrees of  reliability  for use in  refined modeling analysis in
such settings.   Furthermore,  the  need for these models continues to
grow with the  increasing  demands  for energy resource development in
mountainous areas.
     In response to this  dilemma,  EPA authorized the organization
of this Workshop through  the  Meteorology and Assessment  Division
(MD) of the Environmental  Sciences Research Laboratory  (ESRL) at
Research Triangle Park, North Carolina.   The planning and coordina-
tion of the Workshop activities, and  the preparation of this report,
have been carried out  by  North American  Weather Consultants (NAWC)
under contract to EPA, with significant  assistance from the Meteor-
ology and Assessment Division.
     The Workshop was  organized  into five panels on the following
topics:  Model Development and Analysis; Model Evaluation and Applica-
tion; Experimental Design; Measurement Techniques;  Data Management  and
Quality Assurance.  The  number of  Workshop participants totaled  59.
Of these, 47 were invited  specifically to  serve on the  Workshop

panels.  They represented a cross-section  of environmental organiza-
tions, control agencies, industry and  the  scientific community with
technical background and expertise in  complex terrain modeling
and field studies.  The other  attendees  were invited speakers,
guests, and personnel from  the Contractor and EPA contracting

     The Workshop agenda included four  days of  alternating plenary
and work sessions.  The opening plenary session began with presenta-
tions by invited speakers who presented summaries of related complex
terrain dispersion programs currently  being sponsored by  industry
and by government agencies other than  EPA.  This  plenary session
also included opening statements by EPA on their anticipated future
programs and presentations by each Panel  Leader on the goals of the
Workshop and the tasks that the panel  would attempt to accomplish
over the next four days.

     At the end of the Workshop these  accomplished tasks were pre-
sented orally during  the last plenary  session in the form of recom-
mendations by each panel how  EPA should best proceed with the complex
terrain program.  The Panel Leaders handled the tasks of assembling
the written statements from their respective  panels and presented
edited material to the contractor for publication following review by
the panel members.  These statements  are  published, unabridged, in
this report together  with summaries  of stimulating discussions
which took place during the other plenary sessions.


     A Workshop, sponsored  by the  Environmental Protection Agency's
Environmental Sciences Research  Laboratory  (EPA/ESRL),  Meteorology
and Assessment Division  (MD),  was  held  in Raleigh,  North Carolina,
during July 16-20, 1979.  The goals of this  conference were to focus
on complex terrain modeling problems, and to develop recommendations
to EPA with respect to design of a workable multi-year program to
start in Fiscal Year 1980.   Personnel  from the  Meteorology  and
Assessment Division (MD)  of EPA  provided "strawman" material  for
discussion at the conference.  Based on this material, the conferees
agreed that considerable  benefit would  be derived by focusing the
conference on impingement problems.

     Invited experts on  various  aspects of   field studies, model
development, model evaluation, and data management prepared recom-
mendations and technical  support documents  on  these topics and re-
lated budgetary allocations.   The  participants addressed  in  con-
siderable detail questions  on how  to  collect a representative data
base to develop  credible models for  regulatory applications that would
adequately handle plume  impingement problems in elevated terrain.

     The Workshop participants agreed  in principle that EPA should
adopt a two-phased field program  approach, starting with a controlled
experiment on a small, isolated hill of simple geometric setting, and
then proceeding with a large  scale program  of  increased complexity.
It was also recommended  that  the modeling development program follow
multiple development phases.   The  initial effort should be oriented
towards improvements in Gaussian-based models, while the final effort
should be aimed towards  new model  development  incorporating complex
flow fields in rough terrain with either Gaussian-based or "K theory"
based models.  Physical  modeling programs should be an integral part
of the above efforts.

     The Workshop recommendations  address the need for  improved
model evaluation techniques,  statistical analysis methods, sensi-
tivity analysis, comparative  field data analysis, and independent
evaluation techniques.   Furthermore,  informative recommendations
were provided on problems concerning  data management and  quality
assurance, as well as on  specific  costs relative to experimental
design with suggested budgetary  allocations for future programs.



Preface	   iii
Abstract  	     v
Figures	viii
Tables	    ix
Workshop Participants 	     x
Acknowledgements  	 xviii

    1.  Introduction  	     1
    2.  Conclusions 	     3
    3.  Workshop Organization 	     8
    4.  Plenary Sessions  	    11
    5.  Panel Recommendations 	    25
            Model development and analysis panel  ...    26
            Model evaluation and application panel  .   .    62
            Experimental design panel 	    73
            Measurement techniques panel  	    92
            Data management and quality assurance
              panel	   115


    A.  Pre-Workshop material prepared by EPA 	   136
    B.  Pre-Workshop material prepared by NAWC  ....   174
    C.  Post-Workshop comments by panel members ....   184


Number                                                       Page

  1    EPA Workshop schedule 	  10

  2    Diagram of flow of information within program ....  30

  3    Suggested array of samplers for 100 m hill
         experiment	34

  4    Perspective sketch of field program 	  57

  5    Estimation of ambient plume behavior and the
         degree of plume impaction upon elevated
         terrain	75

  6    Schematic depiction of near terrain profiles
         of tracer concentration 	  76

  7    Conceptual depiction of characteristic zones
         of tracer plume transport and diffusion 	  84

  8    Experimental arrangement using laser
         illuminators  	 102

  9    Downlooking airborne lidar showing plume
         contact with ground	110

 10    Interaction between quality assurance and
         data management	116

 11    Example of outlier detection  	 130

 A-l   Diagram showing flow pattern of stack
         plume - nighttime	157

 A-2   Diagram showing flow pattern of stack
         plume - daytime	157

 A-3   Experiment for determinging p(C|P, M) 	 164

 A-4   Experimental design for studying the micro-
         mesometeorology of complex terrain  	 169

 B-l   Flow diagram for Workshop !	179


                        FIGURES (Cont'd)

Number                                                       Page

 B-2   Flow diagram for specific complex terrain
         model study recommendations 	  180

 B-3   Suggested schedule for Workshop as detailed
         by Panel Leaders in their letters to Panel
         Members	181

Number                                                       Page

  1    Summary of measurement techniques and their
         probable applications to experimental scales  ...   94

  2    Single-sensor error checks  	  129

                      WORKSHOP PARTICIPANTS


    Dr.  A.  Paul  Altshuller
    Environmental Sciences Research Laboratory (MD-58)
    Environmental Protection Agency
    Research Triangle Park, NC 27711

    Dr.  David S. Ballantine, DOE
    Office  of Health and Environmental Research
    Mail Stop E  201 (Germantown)
    Washington,  DC  20545

    Dr.  Norman E. Bowne
    The Research Corporation of New England
    125 Silas Deane Highway
    Wetherfield, CN 06109

    Mr.  Edward Burt
    Office  of Air Quality Planning and Standards (MD-14)
    Environmental Protection Agency
    Research Triangle Park, NC 27711

    Dr.  C.  Shepherd Burton
    Systems Application, Inc.
    950 Northgate Drive
    San Rafael,  CA  94903

    Dr.  Jack Cermak
    Fluid Dynamics & Diffusion Laboratory
    Colorado State University
    Ft.  Collins, CO  80523

    Mr.  John Clark
    Meteorology and Assessment Division (MD-80)
    Environmental Protection Agency
    Research Triangle Park, NC 27711

Mr. Jesse H. Coleman
TVA-Air Quality Branch
E and D Building
Muscle Shoals, AL  35660

Dr. Harry E. Cramer
H. E. Cramer, Inc.
540 Arapeen Drive
Salt Lake City, UT  84108

Mr. Loren W. Crow
Consulting Meteorologist
2422 South Downing Street
Denver, CO  80210

Mr. Gerard A. DeMarrais
Meteorology and Assessment Division (MD-80)
Environmental Protection Agency
Research Triangle Park, NC 27711

Dr. Vernon Derr
NOAA-Environmental Research Laboratories
Wave Propagation Lab
Boulder, CO  80303

Dr. Marvin Dickerson, L-262
Lawrence Livermore Laboratory
Post Office Box 808
Livermore, CA  94550

Mr. John Eckert
EPA Monitoring and Support Lab
Post Office Box 15027
Las Vegas, NV  89114

Dr. Bruce A. Egan
Environmental Research and Technology, Inc.
3 Militia Drive
Lexington, MA  02173

Mr. Roy Evans
EPA-Environmental and Support Laboratory
Post Office Box 15027
Las Vegas, NV  89114

Mr. Gilbert Ferber
NOAA-Air Resources Laboratory
8060 13th Street
Silver Spring, MD  20910

Dr. Douglas G. Fox
U. S. Forest Service
240 West Prospect Street
Fort Collins, CO  80521

Dr. Dan Golorab
ORD-Energy Effects Division (RD-682)
Environmental Protection Agency
Washington DC 20460

Dr. Philip Gresho, L-262
Lawrence Livermore Laboratory
Post Office Box 808
Livermore, CA 94550

Dr. Freeman Hall
NOAA-Environmental Research Laboratories (R45X9)
Wave Propagation Lab
Boulder, CO  80303

Mr. Donald Henderson - AIR
National Park Service
Post Office Box 25287
Denver, CO  80225

Dr. Glenn R. Hilst
Electric Power Research Institute
3412 Hillview Avenue
Post Office Box 10412
Palo Alto, CA  94303

Mr. Norman Huey
EPA Region VIII-Air Branch
1860 Lincoln Street
Denver, CO  80295

Dr. Julian C.R. Hunt
Dept. of Applied Mathematics & Theor. Physics
University of Cambridge
Cambridge, England  CBS 9EW

Mr. John Irwin
Meteorology and Assessment Division (MD-80)
Environmental Protection Agency
Research Triangle Park, NC  27711

Dr. Warren Johnson
SRI International
333 Ravenswood Avenue
Menlo Park, CA  94025

Mr. Robert C. Koch
Geomet, Inc.
15 Firstfield Road
Gaithersburg, MD  207GO

Dr. Robert G. Lamb
Meteorology and Assessment Division (MD-80)
Environmental Protection Agency
Research Triangle Park, NC  27711

Dr. Ron B. Lantz
11511 Katy Freeway, Suite 630
Houston, TX  77079

Mr. Thomas F. Lavery
Environmental Research and Technology, Inc.
2625 Townsgate Road
Westlake Village, CA  91360

Mr. Vince Mirabel la
Southern California Edison Company
Post Office Box 800
Rosemead, CA  91770

Mr. Donald W. Moon
Salt River Project
Post Office Box 1980
Phoenix, AZ  85001

Ms. Joan H. Novak
Meteorology and Assessment Division (MD-80)
Environmental Protection Agency
Research Triangle Park, NC  27711

Dr. Robert Papetti
ORD-Air Quality Staff (RD-682)
Environmental Protection Agency
Washington DC 20460

Mr. William Petersen
Meteorology and Assessment Division (MD-80)
Environmental Protection Agency
Research Triangle Park, NC 27711

Dr. Francis Pooler Jr.
Regional Field Studies Office (MD-84)
Environmental Protection Agency
Research Triangle Park, NC 27711

Dr. Rudy Pueschel
NOAA-Environmental Research Laboratories
Atmospheric Physics and Chemistry Laboratory
Boulder, CO  80303

Mr. Alvin Rickers
Utah State Division of Environmental Health
Salt Lake City, UT 84110

Dr. Courtney Riordan
ORD-Office of Air, Land, and Water Use (RD-682)
Environmental Protection Agency
Washington DC 20460

Dr. Ronald E. Ruff
Atmospheric Science Laboratory
SRI International
333 Ravenswood  Avenue
Menlo Park, CA  94025

Mr. Frank Schiermeier
Meteorology and Assessment Division (MD-80)
Environmental Protection Agency
Research Triangle Park, NC 27711

Mr. Maynard E. Smith
Meteorological Evaluation Services
134 Broadway
Amityville, NY  11701

Dr. Ted Smith
Meteorology Research, Inc.
Post Office Box 637
Altadena, CA  91001

Dr. William H. Snyder
Fluid Modeling Section (MD-81)
Environmental Protection Agency
Research Triangle Park,  NC 27711

Mr. Timothy C. Spangler
North American Weather Consultants
2875 S. Main Street
Salt Lake City, UT  84115

Mr. Gene Start
NOAA-Environmental Research Laboratories
550 Second Street
Idaho Falls, ID  83410

Dr. Ivar Tombach
AeroVironment Inc.
145 North Vista Avenue
Pasadena, CA  91107

Mr. James B. Tommerdahl
Research Triangle Institute
Post Office Box 12194
Research Triangle Park,  NC  27709

Dr. Jeffery Weil
Martin-Marietta Laboratories
1450 South Rolling Road
Baltimore, MD  21227

Dr. Michael D. Williams
John Muir Institute
Route 5, Box 229A
Santa Fe, NM  87501

Mr. Dean Wilson
Office of Air Quality Planning and Standards (MD-14)
Environmental Protection Agency
Research Triangle Park,  NC  27711

    Mr.  Robert Wilson
    EPA Region X (MS-329)
    1200 Sixth Avenue
    Seattle,  WA  98101

    Dr.  William E.  Wilson
    Regional  Field  Studies Office (MD-84)
    Environmental Protection Agency
    Research  Triangle Park, NC  27711

    Dr. William R.  Goodwin &
    Dr. Paul D. Gutfreund
    Dames and Moore
    1100 Glendon Avenue
    Los Angeles, CA  90024

    Dr. Don Grey
    Utah Power and  Light Company
    Post Office Box 899
    Salt Lake City, UT  84110

    Dr. Gary M. Klauber
    Environmental Measurements,  Inc.
    1445 Old Annapolis Road
    Arnold, MD  21012

    Mr. Thomas J. Lockhart
    Meteorology Research, Inc.
    Post Office Box 637
    Altadena, CA  91001

    Dr. John E. Pinkerton
    National Council of the Paper Industry
      for Air and Stream Improvement, Inc.
    260 Madison Avenue
    New York, NY  10016

    Mr. Robert N. Swanson
    Pacific Gas and Electric Company
    77 Beale Street
    San Francisco,  CA  94106

    Meteorology and Assessment Division (MD-80)
    Environmental Protection Agency
    Research Triangle Park, NC  27711

    Mr. Lawrence E. Niemeyer
    Mr. George C. Holzworth
    Mr. Gerard A. DeMarrais


    Mr. Einar L. Hovind
    Mr. Max W. Edelstein
    North American Weather Consultants
    600 Norman Firestone Road
    Goleta, CA  93017

    Ms. Victoria C. Sutherland
    North American Weather Consultants
    2875 South Main Street
    Salt Lake City, UT  84115
                               xvi i


     More than 50 individuals  were  involved in the Workshop  pro-
ceedings presented in this  report.  The  contributions  from  this
group,  and in particular  the unstinting efforts of  the panel  members
can best be described as  exemplary.  Several participants  in the
Workshop deserve special acknowledgement,  as indicated  below.

     Advance planning,  assistance in selection of panel  members,
and preparation of  "strawman" pre-conference documents  by Mr.
Lawrence E. Niemeyer,  Mr.  George C.  Holzworth,  Dr. William H.
Snyder, and Dr.  Robert  G. Lamb of the  Meteorology and Assessment
Division of EPA at Research Triangle Park, are acknowledged  with

     The five Panel Leaders, under  whose guidance and motivation
the Panels functioned,  were notably effective in synthesizing  large
quantities of complex technical material into coherent panel reports.
These Panel Leaders are:  Dr.  Bruce A.  Egan (ERT), Mr.  Roy Evans
(EPA),  Dr. Ronald E. Ruff (SRI International), Mr. Maynard E.  Smith
(MES),  and Mr. Gene Start (NOAA-ERL).

     Valuable background  information was provided by special pre-
sentations made by invited  speakers who  summarized the related
complex terrain programs  currently  sponsored  by industry  and by
government agencies other than EPA.   These  speakers were:   Dr.
Glenn R. Hilst,  Electric  Power Research  Institute;  Dr.  David S.
Ballantine, Department  of Energy; and  Dr.  Vernon Derr,  National
Oceanic and Atmospheric Administration.
                              XV 111

                             SECTION 1


     At the request  of  EPA a Workshop was held  in Raleigh, North
Carolina, during  July  16-20, 1979,  to tackle the pressing problems
associated with the  development of  improved mathematical models for
predicting plume dispersion in complex  terrain.  Invited  experts,  with
broad technical and scientific backgrounds, were assigned the tasks of
generating recommendations and guidance to EPA for use  in the planning
of dispersion  model  development and associated field  experiment pro-
grams over the next  3-5 years.

     The manner in which the Workshop  was organized, with five panels
on topics essential  to  achieving the goals of the- conference, is des-
cribed in Section 3, Workshop Organization.  The Workshop schedule
allowed for periodic interchange of technical  information  through
frequent plenary  sessions.

     Brief summaries of opening statements, presentations by invited
guest speakers, and  highlights of the technical discussions, which
took place during these  sessions,  are presented  in Section  4,
Plenary Sessions.

     Under the able  leadership and  direction of five  invited panel
leaders, the panels  addressed  a  number of  technical aspects  of
future EPA programs, as viewed from their respective  specialties.
Not only did the  panels  prepare these written recommendations
under a very limited time  frame, but the participants  also prepared
highly technical reports which the panel  leaders arranged into compre-
hensive support documents  to their  panels' recommendations.  These
statements and recommendations are presented unabridged-in Section 5,
Panel Recommendations,  in  the format presented to the  contractor by
the Panel Leaders.   The proceedings also include some excellent
"strawman" scenarios prepared by EPA and distributed prior to or at
the opening day of the Workshop.  The scenarios served  the stated pur-
pose of introducing the  participant to  some of EPA's internal thoughts
on suitable approaches  to  the problems  at hand.  They also served to
quickly focus  the panels' attention  on critical concepts which needed
to be examined in an  open forurn before  the formulation  of their recom-
mendations.  The  "strawman" plans and other material  and information

distributed to the participants prior to the Workshop, are presented
in Appendices A and B.

     The Workshop  proceedings have also provided a forum for addition-
al comments by participants generated during their review of the final
panel recommendations subsequent to the Workshop.  These letters and
comments are summarized  in  Appendix  C.

     Finally, it  was recognized that the Workshop could only accomo-
date a limited number of  invited participants, and that there were
many highly qualified experts  in the disciplines relevant to  the
Workshop topics who could not  participate in person.  Invitations
were distributed  to over  fifty experts  outside those attending the
Workshop, providing an opportunity for  them  to submit  ideas  and
topics for panel  considerations.   Several excellent  technical inputs
were received and utilized  by  the Workshop panels and recognition
of these contributions is acknowledged  in the list  of participants.

                             SECTION 2


     The Workshop provided a timely forum for technical discussions on
topics pertaining  to  plume  dispersion  in complex terrain.  The dis-
cussions covered a wide range of subject matters dealing with field
study designs,  data handling, and measurement techniques relevant to
the tasks of model development and evaluations.  The EPA "strawman"
plans, which were  prepared for consideration by the Workshop partici-
pants, provided an effective means of  focusing the panels' attention
on specific approaches  to future EPA field studies and model develop-
ment programs.

     The panel  recommendations and associated technical discussions
clearly demonstrate the complexity of  the problems,  and that there
are no simple solutions.   There was general agreement on the over-
all approach regarding  model development programs.   This agreement
was based on acceptance by  the conferees of the  concepts presented
by EPA in their "strawman"  documents (Appendix A) which recommended
focusing on plume  impingement for the  initial effort.   However,
divergent viewpoints  were  frequently expressed by  individual  par-
ticipants, and  at  times by  panel leaders,  regarding the details
of the required experimental studies that would be most appropriate
within the stated  program  constraints.

     The wealth of technical information and panel  recommendations
generated by the Workshop  relative to  the specific  goals expressed
by EPA at the opening plenary session  have  been examined by  the
Workshop coordinators (NAWC staff), and the following  seven  con-
clusions were drawn.


     All panels agreed in principle with an approach to model develop-
ment starting with a controlled experiment on a small isolated hill of
simple geometric setting.  Once an initial understanding of plume im-
paction with elevated terrain is achieved, larger scale experiments
should be conducted,  and  should include systematic investigation of

phenomena with  increased complexity.   General agreement was also ex-
pressed on the  need  for a closely coordinated model development pro-
gram, including the  use of physical modeling techniques, to accompany
the field studies.   The total EPA program  should  be  designed  to
facilitate coordination with other related efforts, such as the EPRI,
DOE, and NOAA programs.

     A lack of  concensus emerged on the question of what physical
hill size would be  preferable for the small-scale program.   Whereas
the modeling panels  considered a 100 m hill to be a desirable size for
simple field experiments on non-buoyant tracer plume impaction, the
panels on experimental  design and measurement techniques expressed,
during the plenary  sessions,  a preference  for a medium size  hill of
400-500 m.  However,  their written recommendations presented herein
are in the form of  pro  and con assessments  with respect to different
field program scenarios, such as small scale  (100 m hill),  medium
scale (400-500  m hill), and full scale (real  plant) experiments in
order to provide EPA with maximum guidance for reaching a final de-
cision on this  issue.  The overriding concerns  in this  decision-
making process  must be  that the scale of experiments can be extended
to  "real world" situations, and they must  be  consistent with  the
ability to measure  the  required parameters.


     There was  general  agrement on the recommended approach that the
initial model development effort should be oriented towards reasonable
"fix-up" to Gaussian-based models currently used in the regulatory
practice.  The  subsequent model development  activities should  concen-
trate on developing and using better descriptions of the flow fields
expected in rough terrain for a variety of meteorological and topo-
graphic settings.  The resultant flow field descriptions  could  be used
with either Gaussian-based models or with  "K  theory"  based  models.


     There was  general  agreement on several recommendations  stating
the need for adequate model  testing and evaluations.  These procedures
should include  examination of model performance  based on observed
versus predicted comparisons.  Emphasis was placed on the need for
having model development data to meet requirements of  model  evalua-
tion with adequate  measurements to verify  model  performance.   The
recommendations also included the need to  define the  applicability
of  the result.   Furthermore,  the demonstration of credibility would
be  greatly improved by  the use of flow visualization.  This technique
enhances understanding  of the  basic processes  occurring  during

plume interaction  with the terrain,  which cannot be readily described
from ground measurements of  tracer concentrations alone.


     The discussion  of  model transferability to other sites centered
around the results to be obtained from the small scale versus large
scale field programs.   It was agreed  that the basic process of plume
impaction in  simple, small  scale  experiments should  be readily
transferable  to  other settings.   However,  the more complex physical
processes associated with large  scale terrain features, such as com-
plex plume trajectories,  thermally induced mountain slope flows,  and
vertical wind  shear, are so  site specific as to make  the transfer of
results to new settings  very difficult.  Again the flow visualization
techniques will  greatly  aid  in the acceptance of  transferability
of the model.

     Specific recommendations regarding model applications include the
need for thorough  documentation of the experiments,  the data, and the
model development.   It is essential that, to assure proper use of the
models, the documentation must include a list of limitations, special
conditions, and  confidence  bands for future  model  applications.


     The discussions on  small versus medium and full  scale  ex-
periments raised many questions  on similarities in  plume behavior.
Doubts were expressed by some whether the surface boundary layer
and vertical  atmospheric structure associated with  the small scale
study would be applicable to "the real world".   Since  turbulent
motion is very important in  the  plume impaction processes with
elevated terrain,  questions  were also raised whether  these processes
can be simulated  on a scale significantly different from that found in
large scale complex  settings.   Other questions were concerned with
plume impaction;  whether  it is dominated by surface induced turbulence
or by turbulence  at plume elevation.  If the former persists, the size
of the hill doesn't  matter,  but  if the latter dominates,  then  the
small hill experiment might  be inappropriate.

     The technical information and discussions generated by each
panel, and presented in  these proceedings are highly illuminating
since they address  these  questions from different technical and scien-
tific viewpoints.  Recommendations were made that field  programs
should allow  for testing the effects of scale,  and that the impaction
problem be studied- as a  function of terrain and meteorology.  There

was general agreement on the recommendation that physical modeling
techniques be incorporated into the model  development program.  The
applications and limitations of this  technique must be defined.


     The primary inputs on data handling  were given by the Data
Management and Quality Assurance Panel.   The  recommendations from
this panel provide  an informative overview of major phases  of
data management  and information  feedback as a quality control
measure.  They suggest that, following  implementation of a Data
Acquisition Plan, the following three actions should occur:  1) Field
operations should provide for field data  through  an acquisition
phase with quality assurance  feedback;   2)  data compilation processes
should follow field data review and bring the data  into a  final
check phase, again with quality  assurance feedback; and   3)  an
independent data review should follow after preparation and delivery
of reports to be accompanied by final quality assurance feedback.
Although field activities are distinguished from off-site activities,
this panel recommended that  the same groups conduct these activities
through the final data archiving process.


     The recommendations prepared by  the  panels  dealing with field
experimental design, instrumentation, and data handling contain a
number of cost estimates and budgetary allocations.   These estimates
must be viewed relative to EPA's expected budgetary  constraints of
about $2.0 million  per year for  three  years.  The Measurement
Techniques Panel presented specific cost estimates for the 100 m hill
and larger scale projects as follows:   For the 100 m hill, hardware
costs alone were estimated to be near $2.6 million and the operation
of the ground-based instruments could be  around $40,000-$50,000 per
month.  Estimates for gaseous tracers,  sampling equipment, laboratory
analysis, towers without equipment, and plume  visualization equip-
ment are also included.  For the larger scale experiments, hardware
costs for Doppler Acoustic Systems could  be around $40,000-$50,000,
aircraft tracer measurements about $8,000  per day, lidar costs about
$50,000 per month, and airborne lidar with ground based data systems
about $4,000 per day.

     The Experimental Design  Panel  prepared a budget estimate
for 50 days of sampling during two 40-day  research periods with con-
tinuous 18 months monitoring  (without centralized data logging equip-
ment) on a 400 m hill in the Western  U.S.  The cost  estimate  was
nearly $2.9 million dollars  based-on  direct  costs  and labor with a

moderate contractor's charges  (General and Administrative expense, and
fee or profit).

     The Data  Management and Quality  Assurance Panel submitted cost
figures based on upper-bound requirements for two field study periods.
The two-phased program would require approximately 12-13 person years.
Personnel and  support costs would consume about one  million dollars,
and field data facilities about $130,000.   The estimated costs were
considered  consistent with the following budgetary allocation sug-
gested by the  Measurement Techniques Panel during panel session dis-
cussions:   management (10%);  field  work and initial data processing
(55%), data analysis and quality assurance (15%), and model develop-
ment (20%).  These proposed allocations were not discussed in depth
during the  Workshop.

                             SECTION 3

                       WORKSHOP ORGANIZATION

     On March 9,  1979,  North American  Weather Consultants  (NAWC) was
authorized by the Environmental Protection Agency (EPA) to organize
and conduct a Workshop  to Develop Recommendations on Atmospheric Dis-
persion Models  in Complex Terrain.  The contract award was  originally
based on a task  requiring NAWC to organize  "a Workshop of invited ex-
perts on atmospheric  transport and diffusion over complex terrain who
will make specific recommendations for  multi-year Government research
that will significantly improve the reliability of practical mathe-
matical dispersion models  over complex terrain".   Furthermore, the
original plan  specified two types of emission  configurations:
"1) Tall chimneys such as  exist at fossil-fueled  power plants and
smelters and  2)  assemblages of emitters relatively near ground  level
such as are expected  in connection with oil shale resources

     During the  first planning meeting between  the EPA contracting
office and the  contractor  (NAWC) in Research Triangle Park, NC, on
March 26-29, 1979, the overall Workshop  effort was modified  to  address
specifically the problem of plume dispersion from large fossil-fuel
power plants in  complex terrain.  Agreement was also reached on the
Workshop structure with plans to have  five panels on the following
topics:  Model Development and Analysis,  Model Evaluation and Applica-
tion, Experimental Design, Measurement Techniques, and Data  Management
and Quality Assurance.

     At the same meeting a list of potential participants  was de-
veloped to include experts in applied and theoretical modeling, physi-
cal (laboratory-scale) modeling, field (full-scale) experimentation,
instrumentation,  data archiving, and quality control.  Consideration
was also given  to obtaining a balance between the panel members' pro-
fessional background  with  representation  from federal  and state
agencies, universities, the electric power industry, and the  private
consulting industry.   Finally, the assignment of the 47 participants
to specific panels was made in such a  manner  as  to provide  some
mixture of expertise, where possible,   on  each  panel.

     A pre-conference  meeting,  scheduled  at  the EPA  facility  in
Research Triangle  Park on June 6, was attended  by  the five  panel
leaders (or  their  substitutes) and the contractor.  By this time,
Raleigh, NC, had been  selected as the site for the Workshop,  follow-
ing considerations of  the cost and convenience of several other loca-
tions.  The  meeting covered technical apects of  the Workshop,  the
respective roles  of the panels,  and final  recommendations  for
the list of  invited participants.

     Subsequently,  NAWC and EPA representatives prepared and  distrib-
uted pre-Workshop  material to panel leaders and members.  These docu-
ments are included as  part of the Workshop report.  Invitations were
also sent to over  50 experts in the fields  listed above  who could not
be included  in  person  at the Workshop, but who were given the oppor-
tunity to contribute construcive ideas and  concerns to the panels for
their deliberations.   Those who responded  to this special invitation
with material for discussion are included in the list of  participants.

     The Workshop  schedule (Figure 1)  was designed to provide maximum
interaction  and exchange of  information between  the panels through
alternating  panel  sessions and plenary meetings.   The opening plenary
session provided the opportunity for  representatives from EPRI, DOE,
NOAA, and EPA  to  present to the participants various programs which
are currently planned  or under way by their respective agencies on
topics dealing  with dispersion in complex terrain.

     The recommendations prepared by each panel during the  Workshop
were presented  to  the  participants during  the final plenary  session.
Draft copies of the statements were distributed the following week to
the respective  panel members for final review.   These statements
represent the panel recommendations to EPA and are presented without
editing by the  contractor,  as agreed during the  conference.

                  JULY 16-20, 1979

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       Figure 1.   EPA Workshop  schedule,

                             SECTION 4

                         PLENARY SESSIONS

     The plenary  sessions were arranged throughout  the Workshop to
serve as a forum  for  exchange of information, as a means to  stimulate
discussions, and  as a catalyst for the individual panels to achieve
the primary goal  of the conference, namely, to develop constructive
guidance and recommendations for EPA.   Section 4 summarizes  the high-
lights of these sessions,  starting with the opening plenary session
and later focusing the attention upon major topics  under discus-
sion during subsequent sessions.

     The first session was devoted partly to the opening statements by
EPA, EPRI, DOE, NOAA  and the contractor (NAWC).  A brief summary of
these statements  in order of presentation is given below. During the
second half of the first session, each  panel leader presented opening
remarks describing the tasks and the goals of their respective panels.
A brief synopsis, with a list of the main topics  for discussion by
each panel, follows.

     The third portion of this section deals  with  questions  and
issues that were generated by the panel  leaders' progress reports dur-
ing the subsequent plenary sessions.   The "strawman" plans  developed
by EPA served the purpose of immediately focusing the participants'
attention upon specific issues.  The material presented herein shows
these issues to be primarily the scale of future field studies rela-
tive to parameters to be measured, considerations in experimental de-
sign and data management,  measurement techniques,  and cost factors.


1.1  Summary of Opening Remarks by L.  E. Niemeyer,  Environmental
     Protection Agency

     Considerations of complex terrain modeling problems  were pio-
neered in the early 1940's by Hewson and Gill and  reached  a  new
prominence a few  years ago when NOAA and the predecessors of DOE and
EPA conducted the Southwest Energy Study.  Other efforts have included
a recent complex  terrain study funded by the  EPA  and contracted by
Geomet, Inc., and the Albuquerque Workshop organized by DOE three


years ago.  Standard Gaussian models have  been adopted, but  the
improvement of the models  has been difficult without  the necessary
funding for a comprehensive evaluation program.  However,  in light of
the recent emphasis on oil shale and coal resource development in the
West, EPA management has earmarked approximately $2.0 million per year
for three years  in order  to  make a significant impact  on  the problem
of modeling plumes from  large  sources in mountainous terrain.

     In a strawman approach  prepared for the Workshop, EPA has sug-
gested three main  directions for studying  the  modeling  problems:

     1)  A small hill  study  to focus on the  key  question of  plume

     2)  A full  scale  study  to verify the  resulting  plume impinge-
         ment module developed under the small  scale  study,

     3)  Other aspects of the modeling problem such as plume trans-
         port, frequency  of  plume impact ion  for comparison with the
         standards,  and turbulence or dispersion statistics.

     The goal of the Workshop is to provide  recommendations  for a
workable program considering EPA ideas but extending and revising them
based upon the  experience and  background of the  participants.

1.2  Summary of  Opening Remarks by Einar L.  Hovind,  North American
     Weather Consultants

     The planning and organization of this conference have  been under-
way since March  1979 when  EPA formally awarded North American Weather
Consultants  (NAWC) the contract to conduct  this  Workshop.  EPA and
NAWC agreed that the  best way to achieve  the  stated purpose, namely to
develop recommendations to  EPA on the problem of plume dispersion from
large fossil fueled  power  plants in complex  terrain, was to arrange a
five-panel Workshop with  about 47 experts  on the following panel
topics:  Model Development  and Analysis,  Model  Evaluation and Applica-
tions, Experimental Design,  Measurement Techniques, and Data Manage-
ment and Quality Assurance.

     The Workshop  schedule consists of  a mixture of plenary sessions
and panel meetings,  starting with this  opening plenary session where
representatives  from EPRI, DOE, and NOAA will provide information on
proposed and ongoing  research programs conducted by the electric power
industry and by  government agencies other than EPA.  It is felt that
this information is  highly relevant to the tasks placed upon each
panel of this Workshop.


     These  tasks will be outlined  later in this session  by each panel
leader.  They will follow a presentation by the EPA Project Officer on
the Workshop Goals, and the manner  in which EPA expects to utilize the
results of  this  Workshop in the planning of future field programs and
modeling efforts on dispersion in complex terrain.

1.3  Summary  of  Related EPRI Research Programs  by Glenn R.  Hilst,
     Electric  Power Research Institute

     EPRI projects that are directly  involved with  complex terrain
problems are  organized under two  main programs.  The  first  is called
the Air Quality  Studies program and has two primary features.  One is
concerned with regional air quality  studies of long  range  transport
and multiple source effects.  The major problems considered under this
program have  to  do with fine particles and their chemical speciation,
source attribution,  and effect on  visibility.  A network of  air qual-
ity stations  is  being instituted  in the western region  for  gathering
information on these problems.  The  second part  of  the Air Quality
Studies is  the Sulfate Regional experiment which is now  in the analy-
sis and modeling phase of its definition of SOg-sulfate relationships.

     The second  major program, which  is more  related  to individual
plume behavior,  is called the Plume  Model Validation  Project.  The
primary goal  is  the collection of substantial experimental data for
the purposes  of  validating models  for their general applicability and
validating  individual predictive  modules, such as plume rise, trans-
port, diffusive mixing, etc.  Toward this end field projects  are being
organized to study plume behavior in progressively more complex situa-
tions, beginning with a plains site, a coastal site, and  then finally,
a complex terrain site.   It is expected that more model development
will take place  with the complex terrain data base, because  knowledge
of plume behavior in these situations is limited.

     In general, it should be recognized that any program dealing with
complex terrain questions is going  to be extremely expensive, and that
the investment will have to be proved worthwhile.  Nonetheless, deci-
sions must  be  made on what is necessary to answer these  questions ir-
respective  of  the cost.   Certainly one way to maximize the benefit
gained from the  various research  efforts is to promote coordination
and cooperation among the interested parties so that the  total of what
is learned  is  more than the sum of the parts.

1.4  Summary  of  Related DOE Research Programs by David S. Ballantine,
     Department  of  Energy

     DOE conducted  a Workshop in Albuquerque in 1976 to address the
poor state  of knowledge of transport  and dispersion in complex ter-
rain.  The  Workshop outlined  a recommended national  effort at a level
of about $30M over  a five year period.   It included a discussion of
the need to study various complex terrain features and characteristic
meteorological systems.

     When new funding did not materialize, DOE redirected ongoing re-
search efforts in the atmospheric sciences and in 1978 began a complex
terrain program  in  the Geysers geothermal area of California.  The
Geysers area  represented a site of opportunity where there was large
scale energy  development and where  considerable data on meteorology
and air quality  had been collected because of environmental concerns.
The focus in  Geysers is on a study  of nocturnal drainage winds.

     Dr. Marvin  uickerson of  LLL was selected as Project Director for
the DOE Atmospheric Studies in Complex Terrain program which bears the
acronym ASCOT.   An  initial two week field study was conducted in late
July 1979 with participation  by LLL, LASL, ATDL, PNL, WPL/NOAA, and a
local contractor ES&S (Environmental  System and Services).  A major
field experiment will be conducted  in September 1980.

     A preliminary  critical review of complex terrain models was con-
ducted by the ASCOT modeling group, which resulted in a recommended
model development program which includes various statistical, dynamic,
and physical  modeling alternatives.

     A longer range program  is evolving for efforts beyond 1981 when
the Geysers study should be completed.  Various options based on con-
siderations of different terrain features, meteorological phenomena,
and relevance to DOE energy  development programs are being examined.
1.5  Summary of Related NOAA Programs by Vernon Derr,  National Oceanic
     and Atmospheric Administration

     The responsibility of NOAA,  and particulary the Environmental Re-
search Laboratory, in this  Workshop, is to aid in assessing the role
of remote  sensors and other sensors (such as aircraft instrumentation)
that NOAA  operates or that  come  from other sources.   The  main objec-
tive is to design and perform experiments to provide a widely appli-
cable data set,  which is acquired with a minimum of measurements and

against which  we  can test models.  In order to do this, several  ques-
tions must be answered regarding such things as the representativeness
of the data, the  resolution in time and space, and the continuity of
measurements required.  It  is also  necessary to determine the  basic
set of weather conditions most concerned with impact, and how to de-
scribe these conditions at  different scales.  Another question  to be
addressed is the  optimum configuration  of remote sensing equipment.

     Remote sensing  equipment includes  a  wide variety of techniques
and measurement capabilities, some  of which are  briefly described

     1)  A three-wave length lidar  system (.347, .694,  and 10.6  m)
         with  polarization  capabilities to identify and trace parti-
         culate pollutants

     2)  A new doppler-lidar system for measuring winds in clean air

     3)  Laser to measure wind or detect  particulates

     4)  Microwave radiometric devices  for measuring temperature,
         and humidity profiles, and  liquid water content

     There are two needs for sensors in this kind of a program.  One
to determine the  prevailing meteorological conditions, and the  other
is to determine the  actual  paths of  the particulates or gases.  For
these needs a  combination of  in situ, aircraft, and remote sensors is

1.6  Summary of Workshop Goals by George C. Holzworth, Project  Offi-
     cer, Environmental Protection  Agency

     EPA has decided that its initial effort in its complex terrain
modeling program  should focus on the problem of terrain impact ion be-
cause this has been  a source of controversy for both the regulatory
agencies and the  power industry, and because it is felt a significant
impact can be  made on this  topic within available  resources.  More
specifically,  the problem has to do  with  a plume in a  stable at-
mosphere encountering one or more terrain  obstacles and particularly
the first obstacle.

     The primary goal of the study will be to generate significant re-
sults as soon  as  possible to demonstrate  what  can  be done with the
funds available.   By significant results  we mean the development of
models with a  demonstrated  higher degree of reliability than current
models in general use.  These models must be reasonable and practical


in terms of requirements  for computing facilities, meteorological
input and plant operations  data.   However,  one way to effectively
improve the modeling results is to specify more representative input
information than is currently required.

     The study plans envision the development of stable impaction
models through a series of  experiments on different scales, ranging
from physical modeling to full scale field studies, which are linked
together to demonstrate their credibility.

     The strawmen proposed by EPA (Appendix A) are suggestions for the
direction of this work.  The goals of the Workshop are to make recom-
mendations on the following aspects  of the study:

     1)  The overall plan

     2)  Model development  approach  and implementation

     3)  Model testing and  demonstration of credibility

     4)  Model applications in new settings

     5)  The scientific feasibilities of proposed field and labora-
         tory studies

     6)  Efficient means  of data handling

     7)  Budget allocations

     In summary, the Workshop is designed to solicit scientific rec-
ommendations on how to most effectively and efficiently impact the
problem of mathematically modeling dispersion over complex terrain and
to do so with available resources.


     The following outline is a synopsis of the major ideas presented
in the first plenary session by each panel leader while addressing
complex terrain issues in general  and the scope of the proposed study
in particular.

2.1  Dr. Bruce A.  Egan - Model  Development  and Analysis Panel

A.   Some of the problem areas associated with complex terrain situa-
     tions that might be  addressed are:

     1)  Regulatory issues (prediction of 3 and 24-hour worst  cases).

     2)  Good Engineering Practice  issues.

     3)  Near-surface releases.

     4)  Long distance transport.

     5)  Low level sources  in a constraining valley situation.

B.   The following are constraints on the scenario developed
     in the Workshop:

     1)  Want a model developed  that will be  useful  in regulatory
         applications for complex terrain settings.

     2)  Need meaningful results on a  timely schedule to  assure
         future funding.

     3)  Program must have  a  high probability of success which pre-
         cludes some approaches  which  may not contribute to  regula-
         tory applications.

     4)  The approaches should complement related  efforts.

     5)  The end products should be able  to  serve  as a basis  for
         future efforts.

C.   Within the constraints  discussed,  some directions are suggested:

     1)  Concentrate on a few  high priority parameterization problems
         (such as the impact  of  a nearby  elevated  source).

     2)  Emphasize the simple  models such as the Gaussian models, but
         collect data that  would be more  generally useful for other

     3)  Relate the simple  field study and physical  modeling  and
         establish uses and limitations for  the  physical modeling.

     4)  Define the flow field and  distortion effects, gradients of
         turbulence levels, and  trajectories  for specific  source

     5)  Separate the flow  field model development and the  disper-
         sion model development.


D.   Questions and Discussions from the Floor are briefly  summarized

     1)  What averaging times are necessary to define the flow field?
         Something considered consistent with the scale of the prob-
         lem which implies 5-20 min in the case of Snyder's strawman.

     2)  In reference to  the point about separating the  flow field
         and dispersion models, software has already been developed
         for treating the problem in this way.

2.2  Mr. Maynard  E.  Smith - Model Evaluation and Applications Panel

A.   Considerations  of various aspects of the planned study  are dis-
     cussed below:

     1)  The focus should be on limited experiments which  would pro-
         vide  maximum information.  In other words,  the  study
         shouldn't become so elaborate that one part of the program
         has to be sacrificed for another.

     2)  It is desirable  to know to what extent wind tunnel  modeling
         can be relied on,  and so comparing this technique  with the
         small scale study is appropriate.  However, this is  not
         likely to be the case in the large scale study  due to the
         additional  complexities of the situation.

     3)  Input data  requirements must be simplified as much as possi-
         ble in order that data be effectively acquired under actual
         field situations.   This means data must  be obtainable in
         reasonable  time  periods and with reasonable instrumentation.

     4)  A panel  of  expert review may be valuable.

     5)  The budget  should  include funds for evaluating and comparing
         the model with  other field data.

     6)  It is important  to consider and define how the model ought
         not to be used,  as well as how it should be.

B.   Comments  from the Floor:

     1)  In response to  the comments on wind tunnel modeling it was
         pointed  out that progress has been made in modeling  drainage
         and convective  transport.  However, this kind of  modeling

         may not  be  widely available  to users involved  in the regula-
         tory process, and could not  therefore be reasonably required
         in that  process.

2.3  Mr. Gene Start  -  Experimental Design Panel

A.   The design of the experiment depends on answers  to some of the
     following questions:

     1)  What is the  goal from the modeling standpoint?   Are we trying
         to test  and discriminate alternate theories? Which models
         should be considered?

     2)  What scale  should be used - Lagrangian,  Eulerian, or both?

     3)  What aspects  of  the problem should be emphasized  -  plume
         rise, impaction,  etc?

     4)  How should  the problem be approached?  This question relates
         to what  measurements should  be taken and what  scale and res-
         olution  are most  appropriate.

B.   Comments from the Floor:

     1)  The point was raised that it is important to design  the
         study so that results will  be visualized  and accepted by

2.4  Mr. Roy Evans - Measurement Techniques Panel

A.   The techniques  selected will largely be dictated by the scenario
     designed and the  site chosen.  A small scale tracer study and a
     full scale power  plant study imply different logistics, some of
     which are outlined below:

     1)  Height rise - measurements  will be simpler  in the tracer
         study because of  lower  altitude  gained  by non-buoyant

     2)  Mixing height -  not scale dependent.

     3)  Tracer species measurements - the tracer study would use a
         fixed ground  based network  to measure tracer  species,  while
         the power plant  study would involve measuring several dif-
         ferent pollutant  species.

     4)  Surface concentrations - simpler  in the  smaller study.

     5)  In-plume measurements - more extensive in full scale study.
         Small scale study is less  suited  for  remote sensing

     6)  Source terms - more complex  in  full scale study.

     7)  Wind profiles, temperature,  and stability - scale is
         larger in the power plant  study so  measurements will be
         more complicated.

B.   Questions and Discussion from  the  Floor:

     1)  What is the value of aircraft sampling when such techniques
         as lidar are readily available?  The  aircraft makes  the
         plume more accessible.  Also,  it  is unlikely that any of
         the techniques would be accepted  without  cross-comparison
         and corroboration with other techniques.

     2)  It is important to distinguish between concentration fluc-
         tuations and plume movements produced by variations in up-
         wind velocity and by turbulence or  separated flow over the
         hill.  It would be desirable to correlate concentrations on
         the hill and upwind velocity fluctuations.

2.5  Dr. Ronald E. Ruff - Data Management  and Quality Assurance Panel

A.   Considerations related to data collection:

     1)  A data acquisition plan based  on  how  data are to be  re-
         corded is needed.  Techniques  vary  from manual to  real-
         time read-out.

     2)  The level of acceptable data accuracy must be established in
         light of instrumental accuracies  of about 10-20% and model
         accuracies of about an order of magnitude.

     3)  Data should be flagged in some way  to indicate its validity.

     4)  Field review and final checks are  necessary in real-time or
         short times in order to efficiently run the experiment.

B.   Considerations related to quality  assurance:

     1)  Instrument Selection


     2)  Operational  Procedures

     3)  Calibration  and Audits

     4)  Checks  on the overall system

     5)  Data  Verification

C.   Considerations related to the  final  product:

     1)  After the data base is assembled, final  validation, correc-
         tions,  and changes must be made  in an  interactive way.


     The primary objective  of the experiment was established early in
the discussions  to be that of an end product which would address the
regulatory  problem by providing a better understanding of impingement
concentrations, particularly with respect to the 3-hour standard.   The
principle controversy arose from considerations of  what was the basic
approach best  suited  to achieving that  end product  (i.e., what size
obstacle to study).  Other discussions  explored  the wide variety of
topics that could be studied within the framework of a given approach,
as well as  the specific methods that could  be used.  The following is
a summary of some of the questions raised and comments made during the
plenary sessions.

3.1  100 m  Hill  vs. 400-500 m Hill

     While  examining the small scale  study approach, the Workshop par-
ticipants became divided over studying a 100 m hill  (as suggested in
Snyder's strawman, Appendix  A) or a somewhat larger  hill.  In general,
those concerned with modeling favored the smaller hill, while those in
experimental design and measurements  preferred  the larger one.

     The advantages of the smaller  hill were seen to be its simple
geometry, its  simpler dynamic influences,  and alleged smaller costs
involved in studying it.  In general, the ease of doing the study (for
example, being able to move  the source around it) would be expected to
result in a more complete data base for addressing the impingement
problem.  Another benefit lay in relating  the results from the small
hill study  with  those from fluid modeling, while being  one level
closer to the  real world.   It was also argued that  the essence of sta-
ble conditions is that the  flow is independent of  height,  so the size
of the hill is unimportant.  Finally, recent experiments in Australia
and Great Britain have tied together turbulence and wind measurements


on 150 m hills  with calculations and laboratory  experiments, suggest-
ing that achieving  similitude is not  out  of  the question.

     The reservations about  the 100 m hill  centered mainly around the
transferability of  the results to real world situations.  In particu-
lar, it was  felt that the surface boundary layer and the  vertical
structure  in the lower atmosphere would not be  representative of the
meteorology  at  plume level  in real cases.   Turbulence processes were
viewed by  some  as being critical to  the understanding of impaction,
and it was feared that the  100 m hill would not allow proper simula-
tion of them.  Another point  made was that,  while the  400 m hill study
would involve additional physical complexities  such  as drainage flow
and thermal  effects, those  complexities are viewed  by some partici-
pants to be  essential in determining  plume impaction.  In addition,
the study  of  the larger hill  would allow the use  of more sophisticated
techniques and  a preliminary estimate was given that the cost would
probably not  be more than 20-50% higher than for  the  100 m hill study.

     The outcome of these discussions was that since no  concensus
could be reached on this issue the decision on what size hill to study
was more properly the task  of EPA management.

3.2  Small Scale and Large  Scale Studies

     The consensus of opinion was that both the  small and large scale
studies ought to be done, with the  small  scale study coming first
chronologically.  The discussion on this topic pointed out some of the
advantages,  disadvantages,  and suggestions for each.

     The primary advantage  of the small scale study  (irrespective of
the 100 m  or 400 m hill controversy) was that its simplicity offered
hope for success at a reasonable cost.  There was also more flexibil-
ity in that  the source could be moved, and the  study could easily be
adapted to examine such questions as those related  to GEP considera-
tions or the effects of plume meander.   The scale  would  be  small
enough that  more real time feedback could be available.  In addition,
it has a close  relationship to physical modeling. Also important was
the idea that with a smaller obstacle, the opportunities for observing
stable flow  in  the proper direction  would be greater.

     On the  other hand, the large scale study was viewed as close to
real world conditions.  Many of the instruments could be more effec-
tively used  at  this scale which would be greater than their  limits of
resolution.   It was suggested that  a site be chosen that was not so
complex as to preclude physical modeling.  Another suggestion was that

some of the  advantages of  the small scale study  should be retained by
using a non-buoyant tracer and movable  source.

     In summary,  it was expected that a combination of the small and
large scale  studies would  produce the most meaningful results as long
as the limitations of each were recognized.

3.3  Measurements

     In general, the kinds  of measurements desired were independent of
the scale of  the  study, while the  specific instruments recommended
were heavily  influenced by it.  At any level, surface concentrations
were considered to be paramount.  Wind field,  stability, and tempera-
ture data were  also critical,  as  were  turbulence measurements.
Flow visualization techniques were emphasized heavily.  Data related
to source terms and dispersion would also be  necessary, and would be
more extensive  during the large scale  study.

     As the discussion turned more to the full  scale study, the empha-
sis on more  sophisticated techniques increased.  Lidar, both ground-
based and airborne, was expected to play an important role.  In situ
aircraft measurements of various parameters also  were considered to be
an integral  part  of the measurement  arsenal.

     While techniques would not always be adaptable to the different
scales, it was  recognized that transfering as  many as possible from
the first study to the next would  be more cost effective.

3.4  Costs

     Relatively little discussion was devoted to costs, however some
specific points were made during the plenary sessions on such items as
budget division and relative cost  of small scale versus large scale

     Early in the discussions a suggested budget division was made by
the Measurement Techniques and Data  Management Panels as follows:
Project Management 10%; Field Work and  Initial Data Processing 55%;
Data Analysis and Quality  Assurance 15%; Model Development and Evalu-
ation 20%.

     During  subsequent sessions, the same panels presented estimated
costs for various field program scenarios.  The  instrumentation alone
for a 100 m  hill  experiment, as originally proposed by Snyder, was
estimated to  be around $2.5 million, providing  real-time read-out from
an array of  towers with 8-level instrumentation.  These figures were


lowered somewhat  as the need for the tower heights and real-time sam-
pling requirements were reduced.   It was noted, however, that  the
small hill  experiments would employ costly in-situ measurements which
would have  to  be  coarser to offset costs.  Also,  on the larger scale,
the argument was  made that more information is returned for the type
of sensors  in  the field.

                            SECTION 5

                      PANEL RECOMMENDATIONS

     This section  contains recommendations  to EPA, which were
generated by this Workshop through the five panels.  They represent
the viewpoints, expressed orally and in writing by the panel members,
which were organized into comprehensive documents by  the  Panel
Leaders.  These statements have been circulated among  the  panel
members for comments before the Panel Leaders submitted them  to the
Contractor for publication.

     It should be noted that very limited time was available for
this process.  The Panel Leaders would have  preferred  more time
for the demanding review, and organizational and editorial tasks to
assure overall continuity and fluency in the statements which follow.
However, it was the expressed desire of the  Project Officer and
Contractor that as much as possible of the written inputs by the
panel members should be retained, and that the publishing of the
proceedings in a timely manner was more important than  editorial
perfection of these statements.

     The following recommendations prepared by the five panels are
presented unabridged as agreed by the Project Officer, Contractor,
and Panel Leaders.


                    PANEL LEADER:  Bruce Egan


        Norman Bowne                 Jack Cermak
        John Clarke                  Douglas G. Fox
        Philip Gresho                Julian C. R. Hunt
        Robert G. Lamb               Jeffery Weil
        Robert Wilson


1,1  Overview of Deliberations
     This panel Twas concerned with generating the basic approach
of the Workshop and the review and selection of the basic scenarios
which EPA should follow in their overall program.  The  panel dis-
cussions concentrated on defining what was  needed to meet EPA's
most pressing needs regarding model improvement for regulatory-
oriented applications in complex terrain.   The panel's approach
was from the perspective of knowing the modeling basis on which
EPA regulatory decisions were now commonly made (e.g. , on the basis
of VALLEY, CR8TER or similar models) and from the conviction that
there was considerable room for improving the physical representations
inherent in the model algorithms, especially in complex terrain

     Implicit in the discussions was the recognition that a descrip-
tive and conclusive measurement program would be required to rectify
the discrepancies in the currently used and presented models.   For
this reason the initial discussions centered on what sort of field
programs would be most useful.  Later discussions centered  on  the
expected nature of the mathematical modeling effort which would be
required both in the short and the long term, the roles that physical
models could play in model development, and the uses to be made of
the measurement data to be collected.

1.2  Perceived Goals of,  and Constraints on,  the EPA Program

     The panel understood that  EPA  was  primarily concerned with the
development of a credible model  for  regulatory  applications involving
the near field impact of  fossil-fuel fired facilities located in the
vicinity of rough terrain.  The  question of the magnitude of possible
plume impingement was of  major  concern.   Other constraints on the
program discussed included:

     •  Overall budget  in the range of two to  two and a half million
        dollars per year  for about  three years.

     •  A need to produce meaningful  and useful end products during
        the program to  help assure  the  year-to-year funding.

     •  The program should .be designed  to have a high probability
        of success in meeting the  goals of EPA.

     •  The program should be designed  to complement other related

     •  The program should result  in  modeling tools with a demon-
        strated high level of reliability.

1.3  Recommended Approach

     The Model Development and  Analysis Panel had a consensus that,
to meet EPA's goals, objectives, and budgetary constraints,  EPA pro-
ceed with a two phase research  plan which involves:

     (1)  A detailed study of the  interaction of a tracer gas plume
with an isolated hill located in otherwise relatively flat terrain.
This study should be performed  on a physical  scale small enough to
allow detailed tracer measurements  at a large number (of order 100)
of locations on the hillside, have the possibility of testing a range
of release heights  and different  release locations,  allow the
use of a variety of flow  visualization  techniques, and allow tower-
based measurements of wind speed and direction  and measures  of
turbulence at a number  of levels above  the surrounding  plain and
above the crest of the  hill.  We suggest that the data need could
be met with a hill of order 100 m high.

     (2)  A further, larger scale experiment  which would build upon
the findings of the first experiment, yet still  be focused upon
obtaining a better understanding of the interaction of an elevated
plume with high terrain.   This  larger scale expriment would allow


the systematic investigation of more phenomena, which in practice
further complicates the problem of predicting ambient air quality
levels in complex terrain settings.   Specifically, this  larger
scale experiment would require more detailed investigations of the
effects of locally-generated,  thermally-driven circulations of
flow patterns, the magnitude and likelihood  of plume impaction,
the effects of wind shear on  dispersion rates, and the  effects
that elevated inversions and other phenomena associated with atmos-
pheric stratification have on plume dispersion.

     (3)  A closely coordinated mathematical model  development pro-
gram having the following elements:

       •  Initial use of existing and appropriate modeling techniques
          in the detailed design of both the small  scale and large
          scale studies.  This use would help assure that monitoring
          sites are optimally  located for maximum  benefit.

       •  Initial model development oriented toward making maximum
          use of data to provide reasonable  "fix-ups" to Gaussian-
          based models currently used in regulatory practice. This
          was expected to take place during  the first two years of
          of the program.

       •  Subsequent model development activites concentrating on
          developing and using  better descriptions of the flow fields
          expected in rough terrain for a variety  of meteorological
          and topographic settings.  It is anticipated  that this
          effort would result  in flow field descriptions which could
          be used  with either Gaussian-plume-based models (by
          defining trajectories and distortion effects)  or with
          "K theory"-based models.

          This was expected to take place in the later two to four
          years of the overall program.

       •  Initial models developed to meet  the requirements of
          routine regulatory use which include; demonstrated improve-
          ment over current methods, relatively easy to  use and
          inexpensive to operate, and capable  of using  a  minimum
          of routinely available input data.

     (4)  Data analysis efforts keyed to providing a better physical
understanding of the phenomena of interest.  This will  involve
qualitative analyses based in  part on the results of flow visualiza-
tion experiments to be performed.   The data analysis  and model


verification efforts should  examine  model  performance (based  on ob-
served vs. predicted comparisons)  using  different levels of input
information.  For example, the  model  performance can be evaluated,
using only data from a nearby airport, only data from an  on-site
meteorological tower, or  using  the more comprehensive data sets from
the detailed measurements to be taken around and on the surface of
the experimental hills.

     (5)  A coordinated and  complementary physical modeling program.
This program should  involve defining the applicability and limitations
of the use of physical models  (wind  tunnel, water towing tank) by
comparisons of results with  the small scale field program.  Based
upon the demonstrations of valid uses of  the physical modeling tech-
niques, these methods might  be  applied to  expand the data base for
testing mathematical models  and to better  understand the flow be-
havior for different terrain configurations.  The results of these
techniques presumably can also  be  used to  help design the  larger
scale field program.

     Figure 2 depicts the expected flow  of information among  the
program elements.

     Several other  comments  about  the panel's  deliberations  and
the reporting herein appear  important to include at this  point:

     (1)  Some of the initial  "scoping" discussions  touched upon prob-
lems of achieving reliable performance with even significantly im-
proved mathematical  models when these were  used to predict the highest
or second highest concentration values expected  during  a  period
of a year, as required by present National Ambient Air  Quality
Standards (NAAQS) and Prevention of  Significant Deterioration (PSD)
rules.  Panel members agreed that  a re-definition  of such standards,
which would require predicting  the highest values occuring  a  few
percent of the time, would make more  sense from a modeling point of
view.  The error bands between  modeled and observed values would be
expected to be much smaller  in  this  latter  case  and greater  re-
liability could consequently be put  on modeling results.

     (2)  It was  decided that, given the constraints of available time
for creating this report and the  nature of  the material to be covered,
it was preferable to not  attempt a major editorial effort to make
the submission totally non-redundant or consistent in style.   It was
also felt that such an editorial effort  would tend to obscure some
of the flavor of individual  opinions  vs.  those better described as
panel consensus, and that the report  would thereby lose some value
to future readers.


  and Verification
                  SMALL SCALE
                 DATA ANALYSIS
                PHYSICAL MODEL
                            LARGE SCALE
                           DATA ANALYSIS
     Parameterization and Verification
Figure  2.   Diagram of  flow of  information  within  program

     The remaining sections  of  this  panel's  report are basically
comprised of contributions by individual  panel  members who volun-
teered to summarize specific topics addressed by the Model Development
and Analysis Panel.  The following topics are  addressed:

     1.  The Small Hill Experiment

     2.  Model Development Activities

     3.  Uses of Field Data

     4.  The Role of Physical Modeling

     5.  Description of the  Full Scale  Experimental Program

1.4  The Small Hill Experiment

     This panel unanimously  agreed that a small scale experiment
(100 m) similar to that proposed in Snyder's "Strawman", and  focusing
on the issue of parameterizing  the highest air quality impacts of
an upwind source during stable, neutral,  and unstable conditions,
would be a good choice to meet EPA's immediate goals and constraints.
The specific advantages of  this  experiment, which were cited,  include
the following:

     •  The results of this  experiment would  address the  major
        modeling problems associated with permitting sources located
        in rough terrain.

     •  The data offered real hope of success  in  improving upon
        presently used modeling methods.

     •  Significant results  could be achieved  at  reasonable  costs.

     •  The experiment can be inexpensively expanded to also  consider
        issues of Good Engineering Practice (GEP) in the presence of
        a terrain object.

     •  The scale and scope  of  the experiment  allowed the  possi-
        bility of providing  real-time or,  at  least, short-turnaround
        feedback on the nature  of the findings.  Along these lines
        it was strongly felt that having a relatively simple experi-
        ment, which was focused on investigating the most  important
        technical issues, would avoid some of  the problems  which
        have plagued other large scale  experiments attempting to
        meet very broad objectives.


     •  The scale of the experiment was sufficiently  small to allow
        extensive use of flow visualization  techniques (such as
        multiple smoke releases on the hill surface) and portable
        meteorological measurement devices (such as  anemometers on
        short masts) to investigate closely  the boundary layer
        flow on the hillside.  The panel felt that such augmentations
        to the basic measurement program would  add greatly  to  the
        overall worth of the program by supplying a  better  funda-
        mental understanding of the flow phenomena  of  interest.

     •  The small scale study allowed the possibility  of  using  a
        relatively mobile source release.  Specifically, the fact
        that the tracer source height could be systematically raised
        and lowered (perhaps even two sources could be released
        simultaneously), and moved to varying distances from  the
        hill, gave the experiment both possibilities of examining
        the relationships (such as source  height to hill  height
        ratios), and would result in a higher data  capture rate
        (the source could be moved on a multi-hour basis to be
        more-or-less upwind of the hill).

     The panel identified priorities to be set for the measurements
to be made as follows:

     (1)  Near-ground surface (breathing  level or less) measurements
of tracer material concentration values in order to provide a direct
relationship of  emission rates  to ambient  air concentrations.

     (2)  Meteorological measurements from several levels on a tower
of at least hill height and preferably one and a half hill heights.
These measures should include anemometry  for the three components of
wind speed and turbulence statistics (e.g., sigma theta, sigma E,  and
standard deviations of vertical and horizontal wind speed fluctuations
averaged over 10 minutes or so).  Differential temperatures and heat
flux measurements should be required.  This tower should be located
on flat terrain away from the hill at a location where,  under prevail-
ing wind conditions, the tower would measure the air flow unaffected
by the presence of the hill.  A second, similarly instrumented tower
(50 m) should be on top of the hill.  A  few  ten to  thirty meter
towers should be located on the sides of the hill.   Tracer measure-
ments should be made on each tower.  Meteorological  measurements
should also include sampling of the vertical  temperature structure
of the atmosphere (temperature soundings and/or acoustic sounders)
and the possible  supplemental  use of a doppler radar for wind

     (3)  Measures (perhaps by remote sensing by lidar of fluorescent
particles) of the elevated plume concentrations and geometry upwind
of the region of interaction of the hill.  Specifically, measures
of sigma z and sigma y were very desirable, provided they were taken
in sufficient detail or over a sufficiently long averaging time, to
produce estimates useful for averaging times as  large as one hour.

     (4)  Flow visualization of flow phenomena - smoke releases,  etc.
Surface smoke releases should be made simultaneously from 25 to 50
well chosen locations to ensure good definition  of the  mean flow
field.  This is essential  for reaching an  understanding of the funda-
mental fluid dynamics of the flow over the hill and Reynolds Number
effects for comparisons with the physical model results.  The smoke
can be photographed by aircraft and ground-based cameras.
     The 100 m hill experiment ws envisioned to have the following
additional characteristics and details:

     (a) An "ellipsoidal" hill should be found which allows study
         of plume behavior approaching both the narrow  and broad
         sides in order to understand the effects of hill  aspect
         ratio on maximum ground-level concentrations.

     (b) On the order of one hundred samplers should be positioned
         on the hill side (not all of which need be run  for each
         experiment).  A suggested array is presented in Figure 3.

     (c) The panel did not feel that it was necessary to have all
         concentration measurements in real time or with sampling
         times of 10 minutes.  On the contrary,  the concern was
         expressed that in order to properly understand the  effects
         of wind meanders, etc., a one hour averaging time would
         be necessary to final interpretation  and extrapolation
         of results.   However,  it was desirable to have a few
         continuous and realtime samplers in the experiment.  After
         an experiment is underway, the tracer release should con-
         tinue from the same location for a duration of  at  least 3

     (d) The panel also did not feel that  it was  absolutely es-
         sential  that the ground-based array  be of such close
         spacing so as to always be able to capture the  plume or
         to always allow direct determinations of the cross-wind
         or vertical dimensions of the plume.   The panel  recog-
         nized that  very narrow  plumes might  miss the sensors


 100m Tower
                                                       TOP (PLAN) VIEW
                                                     24 Sampters Each End
                                                          END VIEW
                                   In1  ^  _*_
 18 Samplers Each Side
 (within dashed ttnas)
                           •   •
                                                           SIDE VIEW
Figure  3.   Suggested array of samplers  for 100 m  hill experiment

         during  some  experiments,  but if  the experiments were
         performed a sufficient number of times, the largest ex-
         pected impacts would be observed.  The model validation
         should be.focused on values  at the high end of the frequency
         distribution of concentrations  -  not just the  highest

     (e) Experiments should be run for all meteorological  conditions
         and should not focus  solely on  behavior during stable

     (f) Several different tracers released at different  heights
         can have the utility of conducting multiple experiments
         within a single experiment.

     (g) Surfaca temperature fields could be obtained by indirect
         techniques (IR measurements from aircraft).

     (h) The statistics of wind flow onto the hill from  a given
         source location should  be  examined  and related to the
         statistics of local wind stations.

     Specific limitations noted for the small scale experiment are
as follows:

     (1)  The wind and temperature structure that an elevated power
plant plume may encounter 300 to 800 m above  the surface  is not
likely to be similar to that through  the first 100 m.  This,  however,
is not likely to affect any conclusions relating to the  ratio of
maximum concentrations in the plume  (immediately upwind)  to those on
the surface.

     (2)  The small hill is not likely to be as thermally and thus
dynamically active as a large hill,  i.e., upslope and downslope flow
will be unimportant.  Also, the surface roughness and processes by
whic'u the plume interacts with the immediate surface will  not be
adequately simulated on the small hill.

     (3)  Only a limited range of source heights relative to hill
height can be examined with a movable tower release.  Specifically,
it may not be possible to have a release height greater than 70 m.
Other methods of releasing the tracer gas from higher elevations
should be investigated (e.g., use of a balloon).

     (4)  The hill is not tall enough to extend up through the
radiation inversion depth where variable temperature profiles and


wind shear effects are important, i.e., processes  that  become  im-
portant for plumes from large power plants will  not  be  thoroughly

     (5)  Boundary layer structures,  like  those found  on larger
hills of different slopes, will not be considered.

     (6)  Only flow on a hill having one aspect ratio can  be explored
in the initial field study.   (Note  that  the physical modeling
techniques may prove to be useful in  expanding  this data base).

     Recognizing the limitations of the results  of  the  small scale
experiment noted above, the panel believes it will  be  necessary
to also study impingement-related phenomena at a larger  scale study
once the results of the small scale experiment have  been analyzed.
However, the small scale experiment is an  essential first step.

     A debate arose in the general Workshop plenary  sessions as to
whether the simple single hill experiment  should be  performed at a
site with a 400-500 m hill or at something as small as 100 m.  This
panel had the point of view that some of the  additional  flow phenomena
to be expected at a 400 m site (local  flows become  more important,
wind shear effects, etc.) would tend  to complicate  the  experiment
and the 100 m hill was slightly preferable from this point of view.
The major conviction of the panel of  the merits  of  the  100  m  size
was based, however, on the expectation that the flexibility and data
capture possibilities at a 100 m hill  site would be  severely compro-
mised at a larger scale site.  The panel was specifically concerned
over the impracticality of constructing a tower of sufficient height,
and the logistical problems associated with  performing the same
experiment on a large scale.   The panel  also felt  that heavier
dependence on remote sensing techniques at the larger site would
not focus as well on the issue of actual ground-level concentrations.


2.1  Introduction

     2.1.1  Objectives.  As evident from numerous  legal debates, a
serious need exists to develop a model  capable of accurately predict-
ing concentration, especially maximum ground-level  concentration,
in the vicinity of proposed sources located in complex  topographic
environments; that is, locations where the  topographic feature
height is a significant fraction of  the  source height (or much
greater than stack height).

     The proposed model development  is  strongly  guided by existing
practice.  Since existing practice includes use of VALLEY and CRSTER,
the model development should  lead to either  improved or substitute
models.  The primary objective of model  development  is to improve
the accuracy of these models  in predicting maximum  ground-level

     2.1.2  Method.  Perhaps the major area of controversy associated
with applications of air quality models is plume impaction on nearby
elevated terrain surfaces.  Recent theoretical developments suggest
that under certain stable flow conditions, plumes  can  impact  on
terrain.  Physical models in  stably  stratified water channels and
wind tunnels of the flows around simple  hills have  demonstrated
that the impaction phenomena  predicted  does in  fact occur,  but
little information exists regarding  the  magnitude of this impact.

     The model development  program will seek  to include results from
the theoretical developments, the field  studies,  and the physical
modeling experiments in order to provide model simulations of plume
impaction.  This represents a step toward improving  the scientific
justification for air quality modeling  and a highly  important step
with regard to application  of the models in  regulatory proceedings.

     For neutral and slightly stable conditions, it is expected that
the conventional Gaussian model can  be  altered to yield acceptable
results.  For the stably stratified  case it  may  be  necessary  to
introduce a separate formulation.

     It is also recognized  that all  significant  situations  in the
application of air quality  models do not involve  simple isolated
hills.  Thus, the model will  need to be  developed in such a manner
that it can be applied to more complex  situations.   It will there-
fore need to be tested against other data previously collected in
addition to that collected  in this program.

     Increased complexity in  the topographic  situation will probably
require development of some form of  meteorological  or flow field
simulation in order to properly direct the plume in complex terrain.
Consideration should be given to the development  and validation of
such a technique within the framework  of this project and given the
constraints of acceptability  for regulatory  application.

2.2  Constraints on Model Development  Program

     It was suggested that  the modeling  program be divided into two
phases consistent with immediate and long-term objectives.


     2.2.1  Immediate (1-2 Years).  This phase is closely  coupled
to the small-hill impaction study and should observe the following
ground rules:

     a.  Should result in useable and valid  improvements to the
         VALLEY and CRSTER models.

     b.  Should be easy and inexpensive  (computer resources) to use.

     c.  Should require a minimum of input data.

     d.  Should be successful in simulating surface concentrations
         from the small-hill study over the range of plume impinge-
         ment phenomena under  very stable  to neutral  stability
         conditions.  Stability in this context is being character-
         ized by the Froude number (Fr) of the upstream approach
         flow given by Fr = U/Nh, where U is the  velocity  at  hill
         height, h, and N is the Brunt-Vaisala frequency.

     The implication of these ground rules is that:  (a) proposals
for changes in existing approved models be given  priority;   (b)  a
variety of existing approaches should be  studied;  (c) little totally
new work can really be developed  (i.e., the first phase modeling
will be based on the Gaussian-type models).

     2.2.2  Long-Term (2-4 Years).  This phase will build on the
first phase, generalize the model where possible, and be developed
simultaneously with the design  and (perhaps) implementation of
the full scale study.  The following ground rules apply.

     1.  Improved methods of estimating the transport  wind field
for application to new "sites" are required.  Locally driven surface
flows (upslope, drainage, etc.) should be considered for inclusion,
as well as a first estimate of  other effects caused  by complex
terrain such as vertical variation (shear) of the wind.

     2.  Should be reasonably economic in terms of computer resources
(storage/execution time).

     3.  Should also "succeed" in describing experimental  results
from the earlier small-hill study.

     4.  Should be capable  of treating different situations equitably
in regulatory applications.

     The implications of the above led to the  following suggestions
for longer term model development activities:

     (1)  A review of the state of knowledge  in  diagnostic wind
          modeling on scales up to 200 krn

     (2)  Development of a complex topography  flow field data  set
          stable and neutral (perhaps also unstable) conditions  for
          for testing diagnostic wind models

     (3)  Early (within 2 years) selection of, at least,  a generic
          model to diagnose wind fields

     (4)  Utilization of the generic model approach to provide
          guid?nee in design of the second phase  field experiment

     (5)  Study of Gaussian and other parameterizations  of plume
          turbulence for coupling diffusion with the flow model

     (6)  Final verification and testing against field  programs
          of combined approach  and initiation of the process  to
          include the new model in OAQPS guidelines.

2.3  Immediate Model Development

     The following steps are suggested:

     (1)  Consideration of the  state of knowledge (capability)  in
          modeling source emissions in complex topography  including
          recent theoretical developments of stratified flow theory
          and results of wind tunnel and water channel experiments
          simulating plume behavior in stratified and neutral flow.
          This effort should focus on the potential use of:

          (a)  2-D potential flow theory as an approximation  of
               the mean streamlines in the horizontal plane  for
               highly stable conditions (Froude number much less
               than one);

          (b)  linearized theory (small amplitude, inviscid approxi-
               mation for moderately stable  conditions (Froude
               number about one); and

          (c)  potential flow  theory for the windward side  of
               terrain features during near neutral  conditions.

     The ability  of  such approximations to adequately  simulate
     interactions between closely spaced topographic  elements
     where  the flow  is dominated by the shedding of vorticity
     should be carefully studied.  This  effort should  also
     review recent findings regarding the motion of stagnation
     points due  to  downstream  vortex  shedding, diffusion
     rates  when temperature gradients vary  considerably over
     the terrain  object, the effects of slope winds on plume
     centerline trajectories,  and the most appropriate ways of
     parameterizing  plume dispersion in separated flow  regimes.

(2)   Critical  review of existing "Recommended"  (albeit defacto
     recommendation) modeling algorithms,  i.e., CRSTER and
     VALLEY as well  as other Gaussian-b?sed models.   Compare
     model  algorithms and assumptions with  theory and experi-
     mental results  as identified in  (1) above.  Develop a
     "matrix"  of  proposed improvements which  considers changes
     in the parameterization in the Gaussian based models of:
     horizontal  and vertical  diffusion,  plume trajectory
     alterations, stability classifications, and space and
     time averaging  effects.

(3)   Proposed  alterations of Gaussian-based models to include
     results of 1-2.  This would include consideration of each
     component "parameterization" in models such as VALLEY and
     CRSTER and the  "matrix" of proposed improvements.  This
     effort could, among other alternatives,  attempt to intro-
     duce terrain correction factors into the Gaussian method-
     ology  and use combinations of diagnostic flow models with
     various diffusion parameterizations to simulate transport
     and diffusion in complex topography.

(4)   Develop/adopt standards  of performance for a  complex
     topography model consistent with those included in the
     EPA modeling guideline  and having a  sound technical

(5)   Testing of the  matrix of improvements  against the field
     data collected  by this study.

(6)   Final  recommendation of specific improvements.

2.4  Long-Term Models

     2.4.1  Diagnostic  Wind  Field  Modeling.   Since even  the best
of the first generation (immediate)  models may stumble in new and
seriously complex terrain  situations,  owing,  in large part,  to the
lack of an adequate  (realistic)  wind field,  the  next generation
of models should be  directed toward  ameliorating this deficiency.
Another concern is the  increased opportunity  for misapplication
of such model vis-a-vis flat terrain Gaussian models.  Towards this
end, models which generate (diagnostically) some sort of a reasonable
3-D wind field should be developed  and coupled  to either  (a)  a
modified Gaussian model, or   (b) a numerical  solution methodology
for the advection-diffusion  equation.   This  model could  be  based
on input data of varying degrees of  detail,  ranging from climato-
logical averages to  a selection  of site specific measured winds.
In all cases, the input data would be  used to generate an improved
estimate of the 3-D  wind field at  a  set of grid points,  the  bottom
surface of which represents  the  topography.   Small-scale physical
models are expected  to  be  useful in  the evaluation of such models.

     The spectrum of such  modeling  approaches  is fairly broad,
ranging from those which simply  generate wind  fields conserving
mass (and do not penetrate topography)  to those in which additional
physics is simulated.   Hopefully,  the  best of these could include
effects of stratified flow, perhaps via a Froude number modification.

     2.4.2  Toward the  "Ultimate"  Model.   Again it must  be  borne
in mind, when examining the  limitations of the second generation
models that even the best  of these (which could be one combining
the best features of these currently available),  even after  being
"calibrated" via the full-cale field data, may not always perform
well in new and different  topographic settings.  The reason for this
is,  as before,  that such models contain insufficient physics  to  always
reliably generate wind  fields which are strongly affected by details
such as terrain shape and  small-scale driving  forces (e.g., drainage
wind and upslope winds), or even  large-scale effects such as mountain
lee waves and the strong downslope winds often assocated with  these.

     Although a fully comprehensive  model would be a desirable end
product, and would be much more generally applicable, it is recognized
that such a model development program  not only requires much more
time and effort than is allotted  under the ground rules, but requires
a greater understanding of flow  behavior under a variety of complex
conditions than is likely  to be  available. For these reasons,  it is
prudent at this time to restrain model  development as discussed


     Nevertheless, it is appropriate to briefly discuss such compre-
hensive models in the event that future programs recognizing the
need are planned, or that simpler models are  found to  be inade-
quately extrapolative.  The comprehensive model would be one which
solves a finite difference approximation to the equations of mass
momentum, and energy conservation on a set  of grid points  which
includes an accurate topographic description.   The  transport  model-
ing could be performed, using  finite difference or finite ele-
ment methods, and turbulence could be modeled either via first-
order (K-theory, with locally varying diffusion coefficients) or
second-order method, either of which must  recognize and address
the current shortcomings of turbulence parameterization.  Currently
such methods give no idea of the statistics of concentration fluctua-
tions (i.e., the effects of averaging times) and cannot be used  for
unsteady flows.  Random walk techniques may be as, or more,  appro-
priate.  Once such a model is developed, it could be calibrated
in the following ways:  (1) Numerous simulations of wind tunnel
results covering a wide range of topographic and thermal variations
(some of which will have, hopefully, been verified against  field
data) and  (2) Several field study data sets, depending largely
on their availability (the data set obtained  from the full  scale
test of this project is a prime candidate)  and completeness.  Such
an approach, while significantly more complex, costly,  and time
consuming (both in development and in computer time), would appear
to have a high probability of ultimate success and could lead to  a
model which is truly general and confidently  applicable to new  and
different potential sites.


3.1  Summary

     In this section of the report we consider the  uses of the data
from the small and large scale field experiments.  This section is
divided into two broad subdivisions.

     1.  Comparing the data with models, qualitative mathematical
         and physical.

     2.  Using the data for improving the models (especially those
         currently used by EPA (e.g., VALLEY, CRSTER)).

3.2  Comparing the Data with Models

     3.2.1   Qualitative Models.  Many air  pollution regulatory  de-
cisions are ultimately (explicitly or implicitly) based on qualitative


models of the flow patterns  and  plume  trajectories.  Therefore, the
first use of the data, especially flow visualization data,  must  be to
help better define  these qualitative models and to  reduce the areas of
controversy surrounding  them.   Specific items  for analysis  are:

     (a)  Identify the range of temperature gradients and wind speeds
that the air flow  passes  around  or  over the hill.

     (b)  Compare  the nature of  the  separated  flow regions  as a
function of Froude number with laboratory experiments.

     (c)  Identify conditions  when plumes are prevented from imping-
ing into hills or  valleys by downslope winds and when they fumigate
onto hills.
     3.2.2  Mathematical and Physical Modeling.   The general approach
governing the comparison  between  the  field data and mathematical
or physical models should  be  to:   1)  use the  data  governing the
approach flow [e.g., velocity field, turbulence  measures, temperature
profile, height and quantity  of plume release, nature of the  hill,
etc.] to predict various  aspects  of  the velocity and concentration
distributions over the hill,  and   2)  to then compare these with the

     A list of some of the useful  predictions and comparisons should

     (1)  Comparisons of  surface  flow patterns over the hill (based
on smoke visualization) with  model predictions as  a function of
Froude number and surface  heating/cooling rates.

     (2)  Mean plume trajectories.  These can  be calculated using
potential flow theory for  simple  hill shapes a priori from the hill
geometry and given Fr and  compared with the observations.

     (3)  The frequency of impinging  plumes and  the local plume
meander in stable conditions.  These  can be related mathematically
to local wind statistics  and  perhaps  the wind statistics  from a
nearby meteorological station.

     (4)  If possible the  velocity and turbulence structure  over
the hill top should be compared with other neutral field experiments
and mathematical/physical  model studies.

     (5)  In the larger field experiment, significant measures
of up and down slope winds are expected including the depth  thick-
ness, velocity, and turbulence of these winds (e.g., in the  Navajo
Vermillian cliffs experiments large up and down slope winds were
observed with velocities of the order of 5-10 m/s and with  layer
thicknesses of 20-30 m).  These measurements  should be compared
with theoretical values.

     (6)  The observed spread  statistics, a  ,  a   , and  maximum
concentration upwind of the hill, on the hill, and over the hill,
should be compared with complex  terrain calculations based on:

     (a)  Pasquill-Gifford spread statistics.

     (b)  Local upwind measurements of velocity fluctuation sta-
          tistics, and the upwind temperature gradient.

     (c)  Measurements over the hill of velocity fluctuation sta-
          tistics, a(z), temperature and wind profiles  and the
          plume centerline locations.

     (7)  Compare the ratio of the surface concentration on  the hill
at one point to the plume  centerline concentration  immediately  upwind
of this point.  Since the location of maximum surface concentration
varies quite rapidly as the wind direction changes,  it is important
that these be compared as a function of the averaging times  of the
plume measurements and of the ground-level concentrations.  These
data will help considerably in interpreting previous field studies
where the averaging times were frequently different.

3.3  Using The Data for Improving Models

     3.3.1  VALLEY Model

     (1)  Impact Ratio.  One major use  of  the experimental data
should be to define the ratio of the maximum ground-level concentra-
tion on elevated terrain to the  plume  centerline  concentration
immediately upwind of the terrain.  These values can be obtained
from the small-scale study as a function of flow field conditions.

     The EPA VALLEY model assumes total ground reflection of the
plume, resulting in a ratio of 2.0, which is thought by some to be

     The measured values of the ratio should be compared to  values
calculated by mathematical models and measured by physical models.


The satisfactory agreement of the model  estimates  with measured
values would allow the applicability  of  models  to  be  extended  to
flow, terrain, and heating/cooling  conditions not  measured in the

     (2)  The Assumed Plume Width a .   Currently the 24-hour average
concentration is based on assuming  that  the plume  is spread  out
over a 22 1/2  sector.  This assumption  must be compared  with ob-
servations and possibly some improved  way  of estimating  this sector
may emerge.

     (3)  Statistics of Plume  Impingement.    This leads to  the
next major use for experimental data,  which is  to  determine  the
frequency of occurrence and persistence of, terrain  impact  flow
conditions in complex terrain.  This  should be accomplished through
long-term (at least one year) continuous  meteorological measurements
to arrive at hourly average flow conditions.  Such data  should pro-
vide the necessary input to the mathematical model  for  determining
second highest concentrations for a given  source during a year for
various averaging times, e.g., 3-hour  and  24-hour.   These estimates
will be site-specific.  However, recommendations might then be derived
which would be generally applicable for specification of  the minimum
(number and type) of meteorological measurements needed at complex
terrain sites to  determine the frequency of occurrence and  persistence
of terrain impact flow conditions.  When a significant  source  of
pollutants is proposed for location  in complex  terrain, these
recommendations can be used to specify the necessary  site-specific
data to show compliance with regulatory  standards.

     (4)  Plume Downwind of a Hill.   Currently  the VALLEY model
assumes that a plume travels on downwind of a hill  with no change
of dispersion rates.  Physical models  suggest that the plume widens
out to the hill's width, b, so that its  concentration is decreased
by (b/a ) where a  is the plume width  prior to  impingement.  Hope-
fully this aspect of VALLEY could be  improved.   (a   is also ex-
pected to increase downwind).

     (5)  Application of VALLEY Model.   Currently  this model  is
applied when dT/dz is greater than a  critical value.  Physical and
mathematical modeling suggests very strongly that  the criteria for
the application of this kind of model  should be based on the value
of a dimensionless number such as the  Froude number.

     (6)  Criterion for Flow Pattern.  As indicated  earlier,  Fr
should be criterion for the flow pattern and for the plume impinge-
ment.  Hopefully, this study should also indicate when strong up or


downslope flows may alter this criterion and change the  value of
the impact ratio.

     3.3.2  Moderate Stability and Neutral Flow Models

     (1)  Terrain Following Models.  In  some models  when the tempera-
ture gradient is less than a critical value, a neutral flow model
of the flow is used.  The simplest of such  models assumes that
the plumes follow a trajectory which remains at the same  source  -
displacement above the hill.  Clearly the experimental results should
be compared with  this model, and the differences noted.  We anticipate
that this model will drastically underestimate maximum surface
concentration - especially for three-dimensional  situations.

     (2)  Interpolative Models.   In such  models some  allowance
is made for the trajectory approaching  the hill surface (e.g., half-
height models).  This approach is an improvement  but is  likely to
be insufficient in many applications.

     (3)  New Models.  New models being developed under EPA contract
are oriented toward regulatory use and may form the basis of im-
proved techniques.  If so, they  should be carefully compared with
the data in both a regulatory manner as well as in a more scien-
tific manner.


     In the last two decades physical modeling of the atmospheric
boundary layer has advanced to a  state that permits accurate pre-
dictions of atmospheric transport and dispersion for many sites
and meteorological conditions.   Two types of facilities  have been
developed that enable thermal stratification of the lower atmosphere
to be simulated.  These are the  meteorological boundary layer wind
and the towing tank (water channel).  Model  studies of  flow and
dispersion around an isolated hill are proposed to:  a) complement
data obtained from the field study,  b) check the degree of similarity
between small-scale model and full-scale data, and  c)  determine
the relative merits of the two physical modeling  methods.

4.1  Background

     The first attempt to study stably  stratified flow over  a
topographic obstacle in the laboratory  was made by  Abe (1929).  Flow
over dry ice in a small wind tunnel produced a crescent  lee wave
downwind of a 1:50,000 scale model of Mt. Fuji that was in qualitative
agreement with full-scale observations.


     In 1934 Prandtl and Reichardt  (1934) designed  and constructed
the first meteorological wind tunnel with a capability  for development
of a thermally stratified boundary layer.  This facility was destroyed
during World War II before  being put to its intended  use.  Following
these early developments Cermak (1958)  designed  and constructed  a
meteorological boundary layer wind  tunnel at Colorado  State Uni-
versity.  This facility and  details of  the early developments  are
described in a paper by Cermak (1975).   The 30 m long  test-section of
2 x 2 m cross-section is equipped with a floor that can be cooled  (or
heated).  Air heated (or cooled) in the return duct  develops stably
(unstably) stratified boundary layers 1 m thick with temperature dif-
ferentials up to 200°F.  This wind tunnel is well suited for physical
modeling of either stable or unstable  flow over  an  isolated  hill.

     The history of towing  tanks to study  atmospheric  motion is
somewhat obscuie.  References to some  early  developments,  and  a
description of the towing tank proposed for physical modeling of
flow over an isolated hill,  are given  by Hunt, Snyder  and Lawson
(1978).  The channel is 1 -  2 m deep,  2.4  m  wide and  25  m long.
The model is towed on a ground board through water  that is stably
stratified by a linear salt-concentration gradient.

     Physical modeling of flow and  dispersion around the  isolated
hill in both facilities is  recommended,  since each type of facility
offers distinct modeling advantages and disadvantages.  Therefore,
comparison with full-scale  results will  help advance the science of
physical modeling while providing data to  complement  the field

4.2  Modeling Criteria

     Similarity criteria for physical  modeling of the atmospheric
boundary layer are given by Cermak  (1971)  and Snyder  (1972).   A
discussion of similarity for stably  stratified flow  around an
isolrted hill is presented  in  Hunt,   Snyder and Lawson  (ibid).

     Two types of similarity should be  considered - similarity of
the atmospheric boundary layer approaching the hill, and similarity
of local flow around the hill.  As discussed by  Cermak (1971),  the
boundary-layer characteristics (excepting for turning of mean wind
direction with height) will  be similar  if the following conditions
are met:

     1.  Equality of bulk Richardson No. (AT/T)gL/U  2 (L = vertical
         distances used to  determine temperature difference, AT).

     2.  Equality of Relative Roughness K /L  for Upwind Approach;
         (L  = length of upwind boundary; K  = equivalent  height
         of roughness elements).

     3.  Reynolds No. UL /(v) in excess of value required to make
         drag coefficient independent of K /L .   On smooth hills
         the location and extent  of  separation appears to  be a
         sensitive function of Reynolds number as well as  K  /L, .

     4.  Equality of relative boundary layer thickness 6/h,  (h =
         height of hill, 6 = boundary layer thickness).

     Local flow around the hill is expected to be similar  if,  in
addition to satisfying the foregoing conditions,  the following
conditions are met:

     1.  Equality of Relative Roughness, K /h.

     2.  Hill-Reynolds No. Uh/(v) is in excess of value  required
         to give similar location of separation for given value
         of Kg/h.

     3.  Equality of product of Hill-Richardson and Reynolds Nos.
         (This is a tentative relationship which needs experimental

                              Ouh\      AT_ hJ
                     A1s   h  /Uhh\       A1s  h
                   g	i 	i  =   g	
                      T  IT,. \  v  /        T  IL

          T  = difference in temperature between hill surface and

     4.   Model hill is geometrically similar  to prototype  hill.

     5.   Surface-temperature distributions are  similar for model and
         prototype hill.  Frequently the Richardson No. for approach-
         flow similarity is replaced by the  square root of  its
         reciprocal  - the Froude  No.  U/[(AP/p)gh] '    (Hunt et
         al,  1978).

4.3  Similarity in the Meteorological Wind Tunnel

     In  the meteorological boundary-layer wind  tunnel, the approach-
flow similarity parameters can be set to cover  the following ranges:

     1.  Bulk Richardson No.  (for entire  boundary-layer depth) -40
         (unstable) to +20  (stable).

     2.  Relative roughness of  upwind approach - as required for site.

     3.  Reynolds No. - usually well  above minimum required since
         L,  = 30 m.

     4.  Relative boundary  layer thickness - approximately equal to
         prototype value.   A  length scale of approximately 1:300 is
         suggested for the  100 m hill;  therefore,  the value of 6/h
         will be about 3 for  the model.

     Local flow similarity  parameters can be varied  as follows:

     1.  Relative roughness of hill - equal  to  prototype.

     2.  Reynolds No. - approximately 7000 minimum for 100_m hill
         or 1:300 scale (U  =  1 ft/s;  h ~ 1 ft;  v*  1.5 x  10

     3.  Richardson and Reynolds Nos.  on  the hill  cannot be  made
         equal to prototype because of h  dependence.  Therefore,
         gravity flows induced by heating and/or cooling  the hill
         may not be similar to full scale.

     4.  Geometrical similarity - as  required.

     In terms of the hill Froude number,  the approach flow  can be
adjusted in the range 0.4 to  infinity for the stable  case and the
same magnitude of parameter change for unstable flow.   Thus, a wide
range of meteorological conditions can be simulated,  including an
elevated inversion.  The latter condition is created by cooling
the upstream wind tunnel floor and warming  a length of floor upstream
of the model.

4.4  Similarity in the Towing Tank

     The approach,  flow similarity parameters,  can be set to cover
the following ranges:

     1.  Richardson No. - in  terms of the  hill Froude No., the range
         of values is 0.1 to  infinity (neutral  flow).

     2.  Relative Roughness of Upwind Approach  - because  of short
         ground board, equality of this parameter  is  not achieved.


      3.   Reynolds No.  - L  is ordinarily too  small to achieve suf-
          ficiently  large values.

      4.   Relative boundary thickness - not equal  (5/h
     For Froude No's,  less  than one, full simulation of the approach
boundary layer may be  relatively unimportant  for achievement of
representative flow around  the hill.   This  is true because flow
passes largely around  the hill with little change of elevation  and
the approach flow  is quasi-laminar.   However, for Froude No's, greater
than one, the upstream flow will almost certainly be turbulent and an
upwind plume may  be transported over the hill surface in the boundary
layer flow.  Accordingly, the towing  tank has some advantage  for
study of plume impingement  at extremely low Froude No's, (including
a range of 0.1 to 0.4  that  the wind tunnel cannot achieve).  On  the
other hand, the wind tunnel has an advantage that plume impingement
can be studied for Froude No's, from 0.4 to 1 and from 1 to infinity
where simulation  of the  upwind boundary layer is essential.  Thus,
through physical  modeling  in both  types of  facility  almost  all
conditions encountered in the field (excepting for some meandering
and low-level jets) can  be  simulated.  Furthermore, for Froude No's.
in the range of 0.4 to 1 both types  of facilities should provide good
simulation and thus provide a good basis for comparison of results.
     The minimum  hill  Reynolds No.  Uh/z v   should exceed  10   for
both facilities.  Therefore,  unsteadiness of the impinging flow  due
to vortex shedding from  the hill should be representative of full-
scale behavior.   At these Reynolds No's, it  is possible  for  the
boundary layer on the  hill  (for a sufficiently rough surface) to
be quasi-turbulent and provide an accurate simulation of dispersion
near the surface.

     Simulation of up-slope and down-slope winds on the hill created
by heating and cooling of the surface is still in the research state.
Full-scale values of the product of Hill-Richardson No. and Hill-
Reynolds No. cannot be attained by  the small-scale models because of
dependence upon the length  scale squared.  Therefore, a satisfactory
modeling of this phase  of flow can be achieved only if dependence upon
this product becomes weak at some attainable value of the product.

     There are several potential benefits to be derived from a com-
parison of physical-model simulations of flow and dispersion about
the isolated hill to the field  observations.   Principally,  the
comparisons would demonstrate the applicability and/or  show  the
limitations of physical  models to this situation.  This demonstra-
tion is especially important for strongly stable flows (F  0.1) past
hills, where plume impingement can occur.  Assuming that satisfactory
correlation is achieved  between the physical model simulations  and
field observations, this study would support further use of physical
models in basic or generic  investigations of flow about obstacles
(such as those of Hunt,  Snyder and  Lawson (ibid),  Kitabayshi, et  al,


(1971), and Lin and Binder (1967).  It would also  lend credibility
to the use of physical models in site specific studies in  complex
terrain where information is required on  the maximum surface concen-
trations.  Furthermore, the measurements  on flow and surface concen-
trations from physical models  could be  used with  confidence  in
testing mathematical models.

     Presently, the simulation of thermally induced upslope/downslope
winds in laboratory models is in the developing  stage.  A combined
simulation of these winds superimposed  on  a mean  flow  toward a
surface obstacle is not foreseen too likely  in the  early part  of
the research program.  However,  in a few  years such  a  combined
simulation may be possible.  Simulation  of thermally induced winds
would be more critical in laboratory modeling of flow about the large
scale  (several hundred meters) terrain feature.


5.1  Objectives

     The objectives of the full scale program are  developed on the
assumption that a small scale experimental program is  conducted at
an isolated hill to define the relationship  between  impingement
concentrations and those of the unimpeded plume.   Objectives  are
listed in order of priority.

     5.1.1  Definition of Flow Fields.   A major  problem in complex
terrain is the definition of the wind field  and  the resultant tra-
jectory of material introduced into the  air.  Since the  transport
of the plume must be known, at a minimum, the wind flow  at plume
height must be defined in detail.   Coupling the  transport  flow
fields at the complex site to the  geostrophic flow field may permit
a method of transferability to be  developed.  At the other extreme,
the local flow field may be coupled to a physical  model  in a  tank
or tunnel.  There are simple models of terrain modified wind fields
in existence that provide a mean wind in  the surface layer.  Evalua-
tion of these models can be  made from a suitable observation program.
If they provide satisfactory estimates of the transport flow field,
a major portion of the complex  terrain  problem will  be solved.

     5.1.2  Impingement.  The major  concern of the EPA is  the impinge-
ment problem, that is what is the  maximum concentration  at ground
level when the plume impacts elevated terrain?  The second objective
of the complex site study is to determine  if findings regarding
impingement can be transferred from the  small scale study to  the

full scale site.  The study  should develop ratios of maximum ground-
level concentration to  free  plume  concentrations as a function of
differences in the physical  and  meteorological  characteristics of
the sites.

     5.1.3  Understanding Physical Processes.   A comparison of im-
pingement effects could be made  on the  basis of  statistics,  but
that would preclude transferability  of  the results to other sites.
An understanding of the physical  processes involved in the transport,
dispersion, and impaction of  the plume  is a primary scientific ob-
jective.  The individual processes of concern include plume  impinge-
ment, occurrence of upslope  or downslope and valley winds,  downwash
or wake effects, depth  of slope  winds  as a function of  surface
temperature field, local turbulence  and effect  on concentrations
and the influence of topography  on the  transporting flow  field.

5.2  Measurements Required to Meet Objectives

     The measurements required to meet  the objectives are discussed
in the following sections in  the same order as  the objectives were
set forth.

     5.2.1  Flow Fields.  Measurement  of the  flow field  may be
measured by a combination of  conventional anemometry on towers near
the source and on prominent  terrain features,  doppler acoustic
sounders and perhaps tetroons.

     Surface wind measurements will  provide information on slope
winds.  Since the primary objective  of  knowing  the flow field is to
determine plume trajectories, it would  seem that direct measurement
of actual plume trajectories  would be most useful.   This could be
accomplished by aircraft mounted lidar  tracking.

     The time scale of  observations should be sufficient to  evaluate
turbulence, but short enough  to  approximate straight line segments.
Average values of direction  and  speed for periods of 10 minutes,
to not more than one hour, are considered appropriate.   Spatial
scales are unknown at this time  and  are dependent on how much the
topography actually influences wind flow  at plume height.   Comparison
of plume or tetroon trajectories, with  mixed measurements  provided
by towers and doppler acoustic sounders recommended here,   should
provide answers to this problem.  The outcome of an intensive plume
tracking experiment in  this  program  should be directed to supplying
requirements for a minimum density of measurement  devices.   Rawinsonde
observations should be  made  to tie local observations to the routine
synoptic scale observations.


     5.2.2  Impingement.  Direct measurement of impingement concentra-
tions must be made  on prominent terrain obstacles subject to impinge-
ment.  The time scale of  concentration measurement must be appropriate
to the air quality  standard.   Consecutive hourly values that  can be
averaged for periods up  to 24-hours are required.   In addition, a
measure of plume concentration in the free air prior to, but close to,
the impingement point must  be measured.   The time average of this free
air measurement  must be  the same as the basic  time  of averaging of
the ground-level concentration.  The source term, that is the emission
rate of the quantity whose concentration is being measured, must be

     Spatial variability of concentration patternss will be high.  It
is not practical to have  enough sensors on the terrain obstable  to de-
fine the maximum.   A rule-of-thumb generated years  ago states that
there should be 10 samplers in six standard deviations of the Gaussian
plume to define  the maximum concentration with good reliability.
Even using tracer  samplers such  density  is  unlikely.   However,
continuous sampling to achieve a large number  of  samples with time
rather than space  can be substituted  in an attempt  to capture the
maximum concentration. Therefore, continuous sampling is recommended.
Physical modeling  may be used for development of flow fields, fill-in
concentration and wind fields, and provide a basis for model-prototype
comparison to evaluate validity of model results.

     5.2.3  Physical Processes.  In the section on  objectives, it
was noted that  the ability to transfer results to other complex sites
is desired.  In  order to understand the physical  processes  listed
in Section 5.1.3,  the necessary measurements must be made in adequate
detail.  These  are listed and discussed.

     Impingement frequency - a combination of plume visualization and
surface measurements is required.  The areas where  impingement is
expected on the  basis of climatology  and physical  modeling  should
have measurement capability.   Plume tracking by  lidar or photography
of a visible plume will  also provide such data.  There must be  enough
observations to  describe the frequency of occurrence of impingement
with respect to  specified flow patterns.

     Slope winds - it is expected  that upslope and  downslope winds
will be major mechanisms affecting plume concentration at the ground.
The occurrence,  strength,  and depth of the slope  winds  should be
measured by local  anemometry or with  visual means,  such  as  smoke
tracers and photography, to establish the  relationship between
observed concentration and flow.  Measures of ground temperature and

surface heat flux are  also  required.   Hourly  averages  should be

     Downwash or wake  effects  - if the plume  is in the lee of  a
ridge or hill affecting  the vertical  position of the plume, the
magnitude of the displacement  should be documented by indirect
measurements with lidar  or  DIAL systems.  The measurements  should
be sufficient to establish  any wave pattern with distance, as well
as fluctuations in heights,  at a fixed point.  Hourly mean  values
with estimates of the  fluctuations, if the fluctuations affect the
final stabilization  height  or  ground-level concentration, are re-
quired.  Wakes behind  obstacles,  such as an isolated hill or ridge
lines, may seriously deform the plume.  If such events  occur, they
should be measured by indirect means such  as lidar or COSPEC.  Concen-
tration will probably  be too low for successful use of a DIAL system.
The expended width and/or depth of the plume should be measured and
analyzed as a function of obstacle parameters and plume  size before
encountering the obstacle.

     Slope wind depth  -  if  slope winds are found to affect ground-
level concentration, then it will be  necessary to analyze them in
more detail.  It has been suggested that slope winds may  be  cate-
gorized as to depth and strength as a function of surface temperature.
Radiometric measurement  of  surface temperature by aircraft mapping
or regular thermometry may  be  used.  A need for hourly  values over
a wide area would suggest standard methods  rather than aircraft

     Local turbulence  -  the local turbulence will be responsible for
diffusing a laminar  plume flow  onto the hillside in stably stratified
conditions.  But plume meander, which  strongly affects the concentra-
tion at a point, is  not  caused by local  turbulence, but by unsteadi-
ness in airflow around the  topography (e.g., vortex shedding).  If
local turbulence is  a  function of surface roughness and heating (and
it better be), then  direct measurement of turbulence intensity should
be related to local  concentration.  If the relationship  is measured
at several points to establish patterns  and if patterns are found to
exist in a quantifiable  form,  then a  method of transferring findings
to another site exists.  The turbulence measures should  be averaged
over the same time period as the basic concentration measurement,
i.e., one hour or less.

     Influence of topography - in Section 2.1 it was noted that the
topography influence on  plume  trajectory was  important and that
trajectories would be  studied.  The purpose of this section  is to
provide measurements,  either direct plume measurements or indirectly


by wind measurement, of the influence  of  specific terrain obstacles
on the wind pattern at plume altitude.  The  purpose is to establish
standing patterns as a function  of  geostrophic wind direction and
terrain aspect ratio.  Hourly averages should provide sufficient
time resolution.

5.3  Description of Field Program

     The previous sections outlined the objectives and the measure-
ments necessary to meet those objectives.   The measurements  were
stated on an individual basis.   In  this section we provide an  over-
view of our estimate of the field program necessary to obtain the
measurements in an integrated manner.

     Figure 4 is a sketch of the field program except for pollutant
or tracer ground-level concentration measurement sites.   Routine
measurement of some variables are called for all the time.   Intensive
periods of measurements are interspersed  for more detail.

     5.3.1  Routine Measurements.  A meteorological tower of at  least
100 meters should be erected,  if  it doesn't  already exist at the  site,
to measure temperature, temperature  difference,  wind  speed and
direction, and turbulence near  the  source on a continuous basis.
Additional shorter towers should be located on the top of the hill
to measure wind speed and direction,  temperature,  and turbulence.
Turbulence measurements should  be three-dimensional.  Other  ane-
mometers and temperature devices should be placed in the valley and
on the valley sides  to measure slope  winds routinely.  Two u,v doppler
acoustic sounders should be employed in the valley to profile the
wind above the tower.  Rawinsonde observations should be made 2 to 4
times per day.  These routine observations  will establish the general
climatology of the temperature  and  flow fields of the area.

     Routine measurements of ambient concentrations of stack  gases
should be made to establish concentration patterns.  Fifteen to
twenty fixed monitoring stations should be  located on  prominent
terrain features and in the valley  to establish the annual distribu-
tion of pollution patterns and  frequency distributions of concentra-
tions at a point.  Hourly averages  should be acquired.  Pollutants
to be measured, in order of  priority,  are  S02,  NO-NO  ,  and 0,,.
In addition, routine high volume air sampling for total suspended and
respirable particulates should  be carried out on a 24-hour basis.

     5.3.2  Intensive Periods.   Intensive measurement periods of 4
to 6 weeks duration should be carried on  as usual, but additional,
more detailed measurements would be added.



     Two aircraft should be employed.  One containing  a particle
lidar will be used to determine plume position out  to  distances of
50 km or more for as many hours as the crew and equipment can  be
used.  The second aircraft will be employed to fly through the plume
to establish free air concentration patterns of gases.  Sufficient
passes must be made  over a  fixed position  to establish hourly
averages for relationship to ground-level monitors.

     A ground-level lidar and perhaps DIAL  could be  employed  to
examine near field plume behavior for downwash effect,  trajectories
and plume position.

     The ground-level monitoring network  is not capable  of providing
adequate spatial resolution  of  concentration patterns.   Tracer
studies are recommended.  Tracer material may  be  released either
continuously or for specified periods during each intensive period
and sampled at 200 locations.  Samples should be collected for one-
hour periods each.  Currently available  samplers are  capable  of
collecting 12 to 24 samples  on preset timing using  battery  power.
Suggested tracers are SFfi or perf luorocarbons utilizing gas chromato-
graphic analysis.  A few (up to 5) continuous tracer monitors should
be employed to provide a time  history of  tracer concentration.

     One member suggested the tracer not be  injected  in the stack
but released from a tower.   Another member felt  strongly  that the
tracer be emitted from the  stack because  plume rise is a significant
part of the problem.  An alternative of  using both methods was also
suggested; the latter (tower release) being  used  to systematically
investigate the effects of  different release heights.

     5.3.3  Analysis Timing.  Real time  collection  of  some  of the
meteorological information  is required to plan special intensive
measurements such as tracer  studies.  Real time collection of other
data is not required.  Unlike the isolated hill,  fast  turnaround,
i.e., the next day, is not  likely to be  available and should not be
necessary.  However, it is  important to  complete  the analysis  of
data from one intensive period before going  to the  field for  the
next period.

5.4  Model Development

     The model development  effort that is a part of the large scale
study should focus on the flow fields rather than the plume dispersion
and impingement processes.   The main objective should be the develop-
ment of a technique by which the three-dimensional flow and tempera-
ture fields within the atmosphere's first kilometer can be described


quantitatively given the geostrophic flow  conditions,  the specifica-
tions of the local topography, cloud cover,  etc.  Flow and temperature
information is required to model plume rise, dispersion, and center-
line trajectory; the Froude number of hills  in the  plume's path
(needed to make concentration estimates on the hill); and, perhaps
most importantly, the annual frequency with which  plume  impaction
on particular terrain features is likely  to occur.

     Flow models of several types should  be developed.   Physical
models should be developed for the terrain site investigated in the
field and its simulated flow and temperature  fields  compared  with
those actually observed.   A demonstration that physical  models provide
reliable simulations of the microscale flow regime  characteristics
in complex terrain would help make this type  of model  a  credible
source of flow data for other sites.

     Numerical flow models should also be developed.  A  number of
"linearized" models currently  exist  that could be  validated  or
perhaps refined using the meteorological  data gathered during  the
large scale field study.  If these simple models prove to be inade-
quate, far more advanced  (nonlinear)  numerical models  should  be
developed.  In this case a constraint on  the  model  design  must be
that the computer time and memory requirements be small enough that
the model can run on machines accessible  to a majority of potential

     Finally, simple empirical models can be  developed that would
provide for given geostrophic flow and topography  specification
(for example, valley depth, width,  length,  etc.),  estimates  of
drainage flow speed, stability and depth; vertical profiles,  wind
speed and direction over the valley floor, etc.  This model would
be used to provide information for plume  rise  and  spread estimates
and frequency of occurrence of given  plume trajectories.

     In addition to the flow field modeling,  part  of the effort of
the large scale study should be devoted to the development of plume
rise and spread  models  that are  applicable  to complex terrain
environments where extreme variations in  wind  direction  and speed
and temperature can occur in the vertical.   Two-particle, Monte
Carlo type models are the simplist models that are  best suited for
this purpose.  The same model can also simulate the plume centerline
trajectory and spread given the 3-D flow  and temperature fields and
information on the flow meander frequency and intensity.


Abe, M. , 1929:  Mountain clouds,  their  forms and connected air
     currents.  Bull. Central Meteor. Obs., Vol 7, No. 3, Tokyo, 1929.

Britter, R. E. , J. C. R. Hunt, and J. S. Puttock,  1976:  Predicting
     pollutant concentrations  near buildings and hills.   Symp.
     Systems and Models in Air and Water Pollution.   Institute  of
     Measurement and Control, London.

Cermak, J. E. , 1958:  Wind tunnel for the study of  turbulence in the
     atmospheric  surface layer.   Fluid Dynamics and  Diffusion
     Laboratory,  Tech. Rept. CER58-JEC42, Colorado  State University,
     Fort Collins, Colorado.

	, 1971:  Laboratory simulation of the  atmospheric boundary
     layer.  AIAA Jl., Vol. 9, No. 9.

	, 1975:  Application of fluid mechanics  to wind  engineering,
     ASME Jl. of Fluid Engineering, 97,  Series 1, No. 1.

Hunt, J. C. R. , W. H. Snyder, and R. E.  Lawson, 1978:  Flow structure
     and turbulent diffusion around a three-dimensional hill.  Tech.
     Rept. EPA-600/4-78-041, Environmental Sciences Research
     Laboratory,  Research Triangle Park, North Carolina.

Kitabayski, K. K. , M. M. Orgill, and J. E. Cermak,  1971:  Laboratory
     simulation of airflow in atmospheric  transport  - dispersion over
     Elk Mountain, Wyoming.  Tech. Rept. CER70-71 KKK-MMO-JEC65,
     Fluid Dynamics and Diffusion Laboratory,  Colorado  State
     University,  Fort Collins, Colorado.

Lin, J. T. , and G. J. Binder, 1967:  Simulation of mountain lee waves
     in a wind tunnel.  Tech.  Rept. CER 67-68 JTL-GJB24, Fluid
     Dynamics and Diffusion Laboratory,  Colorado State University.

Prandtl, L., and H. Reichardt, 1934:  Einfluss von warmeschichtung
     auf de Eigenschaften einer  turbulenten Stromung.   Deutche
     Forshung, No. 21, Berlin.

Puttock, J. S.,  and J.  C.  R. Hunt, 1979:   Turbulent diffusion  from
     sources  near  obstacles with separate wake - Part 1.  Atmospheric
     Environment Vol.  13,  No. 1, pp. 1-13.

Sherman, C. A. ,  1978:   A mass-consistent  model for wind fields  over
     complex terrain. Journal of Applied Meteorology, Vol. 17,  No. 3,
     March 1978, pp. 312-319.

Snyder, W. H., 1972:  Similarity criteria for  the application of
     fluid models to the study of air pollution meteorology.   Boundary
     Layer Meteorology, Vol. 3.


                 PANEL LEADER:  Maynard E. Smith


     Edward W. Burt                    John S. Irwin
     Harry E. Cramer                   Vincent A. Mirabella
     Loren W. Crow                     Alvin E. Rickers
     Donald Henderson                  William H. Snyder


     Our panel reviewed the stated objectives and priorities of  the
EPA group, and attempted to adapt its discussions to respond to  the
Agency's needs.  As we understand them, the objectives are:

     A.  To establish as accurately as possible the maximum concen-
         trations found when a stable plume impinges  directly on
         a local terrain obstacle.

     B.  To determine whether the diffusion or distortion  of  the
         stable plume differs from that over flat terrain prior
         to its intersection with the terrain.

     C.  To consider what input data would be required to make  use
         of new or altered models developed  for evaluating such

     Because our panel was expected to address the question of appli-
cations, we tried to keep the regulatory aspects of the problem in
mind during our deliberation.  For this reason, we would require  the
contractor to relate the experiments to the National  Air Quality
Standards or PSD increments.

     To implement these objectives and meet our responsibilities
with respect to the evaluation and application functions, we estab-
lished an outline of discussions which included:

     A.  A set of end products or desired results of the studies.

     B.  Consideration of the role of modeling within the experi-
         mental studies and  in  the application of the  results.

     C.  Consideration of the specific field experiments  needed.

     D.  The evaluation of the field data.

     E.  The application of the results to  regulatory problems.

     F.  Additional topics which we believe  EPA should  consider
         with respect to complex terrain and modeling.


     As stated in the Workshop "strawman", the air quality modeling
system is being designed "to produce atmospheric dispersion models
that are applicable to large sources in complex terrain  and  that
have a demonstrated higher degree  of reliability  than  existing
models".  This basic objective outlines the major end product ex-
pected from the modeling program.  This end  product will be the
result of either the refinement of existing Gaussian models or the
development of new models embodying advanced techniques and using
the data base collected during the field experiments.

     In order to accomplish the study objectives,  and to allow proper
interpretation of results for regulatory application, it is necessary
to determine the wind, turbulence,  and concentration fields  as
functions of both time and space.

     In terms of time resolution,  a required  end  product is  to
obtain concentration measurements for averaging periods  ranging
from ten minutes or less to as long as three hours.  Consideration
of this time range will permit the interpretation and proper ex-
tension of modeling results to be compatible with applicable  stan-
dards.  These time average specifications should,  to the extent
feasible, be augmented by continuous concentration measurements to
provide an accurate characterization of the fine-scale structure of
the three dimensional wind, turbulence, and concentration fields.
In addition, a methodology must be developed for assessing plume
impacts up to a twenty-four hour averaging period.

     In terms of the spatial scale to be examined,  strong emphasis
should be placed on developing the modeling capability for describ-
ing near-field impacts, i.e., source-terrain separation distances

ranging up to several kilometers.   Consideration of long-range
transport, and its associated problems,  should not be within  the
scope of these impingement experiments.

     An additional and very important end product of the  study
should be an assessment of the transfer value of the experimental
results to other locations.

     We believe that this project should include  the following:

     A.  Specific evaluation of  presently used "off-the-shelf"
         models with inclusion of confidence limits.

     B.  Delineation of model applicability  and  limitations of
         modeling results.

     C.  Specification of minimum meteorology and  source input  data
         necessary to provide reliabile impact estimates.

     D.  Determination of the concentration probability distribu-
         tions of the test data.

     E.  Examination of the meteorological conditions likely to
         cause the highest second-highest limiting concentrations
         in complex terrain for the three-hour and twenty-four
         hour averaging periods.

     F.  Recommendations for further research efforts to extend the
         results of this study to other terrain configurations and
         time-averaging periods.

3.    MODELS

     The details of the models that will evolve from these  plume
impingement studies cannot be specified a priori.  However,  there are
certain model features and modeling criteria that  should be addressed
prior to the experimental  design to insure the adequacy of the  design
and to facilitate the application of the results to  real sources.  We
believe that it is very important to develop at the outset a model
construct that contains, in as much detail as possible,  all  of the
basic terms and parameters that will be required  to analyze  the
measurements obtained during the experimental program.  It should
also provide for the generalization of the  modeling techniques
developed from the experimental data, so that these techniques can
be applied to specific sources and terrain situations.

     The basic model  construct  should  include  characterization of
the following:

     A.   Source

     B.   Stable Approach Flow

     C.   Plume Characteristics  Prior to  Impingement

     D.   Impingement

     E.   Hill Surface Boundary  Layers

     F.   Ground-Level Concentrations

     G.   Time Averaging

     A prototype model construct  containing these factors should be
developed and used to calculate expected ground-level concentration
patterns for various  combinations of stability,  aspect ratio,  wind
speed, Froude number  and other  critical  parameters for the experi-
mental terrain factors.  One should also remember that various
hypotheses may apply,  and a single model construct  may not be

     The importance of the prototype model construct and  calcula-
tions is that they will force specification  of  source,  meteoro-
logical, terrain, and flow parameters  that  control the various
processes, and provide an objective framework  for experimental
design,  data analysis, and model  development.


     Our panel decided that two field  experiments are  desirable,
one on a relatively small scale and the  other on the  scale of a
major terrain obstacle.  The first at  least should be  replicated
in a fluid modeling facility.

     It  is important  that flow  visualization should be  conducted
before either sampling network  is made  final.    Such tests would
insure appropriate placement of the sampling equipment,  and might
provide  valuable information on  the diffusion, aerodynamic and
transfer processes as well.

     Real-time measurements of  the meteorological variables,  and
some of  the key concentration measurements,  would be  helpful in


managing the experiments,  but much of the concentration data need
not be immediately  available.

4.1  Small Scale

     Partly because of concern about extrapolating the results of
a small-scale  experiment to very large terrain features,  and  partly
because of the interchange of ideas with other  panels, we debated
the relative merits of 100 m versus 400 m hill experiments at length.
The conclusion was  that the 100 m experiment was a better choice for
numerous reasons,  the primary ones being that (a) the work would be
easier to accomplish,  (b)  it appeared to have a much greater  chance
for success in illustrating, measuring, and understanding the physical
mechanisms involved in the transport and diffusion of pollutants
through the atmosphere to  the hill surface.  We had no objection to
a larger hill  experiment if all equivalent measurements were made.

     The panel also debated the relative merits of the 100 m hill
(Snyder) versus the 25 m hill  (Lamb) experiments.  The latter appeared
overly complicated and was  likely to be too often submerged within the
turbulent surface layer under very stable flow conditions.  A natural
100 m hill would  extend above the turbulent surface layer much more
often, and it  was our first choice.

     The details  of the experiment received considerable attention,
especially with respect to measurements which would insure physical
understanding  of  the mechanisms involved.  We recommend:

     A.  Meteorological Measurements.  Wind speed and direction, tem-
perature, and  three components of turbulence intensity up to at least
1.5 times the  hill  height  on each of the main towers:  these data to
be logged for  the duration  of  the study periods (twenty-four hours per
day for three  to  six months) not just during tracer release periods.

     B.  Concentration Measurements.  A  sufficiently dense network of
samplers on the hill surface as well as a  few  above the shallow
(turbulent?) surface layer would show whether there may  be  sharp
concentration  gradients near the hill surface because of stagnation,  a
turbulent surface layer, or katabatic winds.  It would also help in
understanding  of  the key processes involved in the transfer of  pollu-
tants from the laminar approach flow to the surface itself.

     C.  Hill  Surface Layer Measurements.  Attempts should be made,
preferably through  relatively simple means (possibly smoke releases,

smoke rockets, wool-tuft grids,  etc.).  to determine the main charac-
teristics of  the  surface layer on the hill, i.e., its depth, speed,
and direction  over  the entire surface of the hill.

     D.  Source Placement.   The placement of the source, vertically
and horizontally,  is very  important,  especially since the stable plume
is likely to  be exceedingly thin in the vertical.   Indeed,  upon
further discussion,  it was  deemed essential to  "fatten" the source
artificially.  The  tracer could be released through  rakes of small
tubes distributed in the  vertical and  horizontal directions to obtain
expanded initial  plume dimensions,  a zo and ayo.

     E.  Averaging  Times.   It is recommended that the source be fixed
during a given test period  (  three  hours) and that the concentration
measurements  be made (in segments not to exceed ten minutes) during
the full three-hour period.  The panel felt that averaging times of
ten minutes or less  were essential in order to understand the physical
mechanisms involved  (e.g., so that a  "plume-meander factor" can be de-
termined), but it was concerned about possible  misapplications or
extrapolations from ten-minutes  to three-hour averaging times.

     F.  Hill  Shape.  A hill, ellipitical in plan view with an aspect
ratio of approximately 3:1, is preferred.  Early  investigations of
wind distributions  and smoke plume  visualizations are recommended to
insure that the winds frequently blow in a direction nearly perpen-
dicular to the major axis of the ellipse.

     G.  Synoptic Data.   While synoptic data are believed to be un-
necessary for  the conduct of the small scale experiments, they may
become valuable in  specifying model input data  or  in transferring
the results to other terrain features.  We therefore recommend that
they be obtained  at the  time of  the tests and included in the data

4.2  Large Scale

     The basic types of meteorological  and concentration measurements
required for  the  small scale experiment are also  required  for the
large scale experiment.   The criteria, with respect  to the terrain
geometry and  the  expected frequency of stable flow in the direction
of the terrain, are in principle the same for both scales.  The large
scale experiment  offers  a choice of sources, a  real  source (power-
plant stack plume)  or a simulated source (tracer).  The use of a real
source has the advantage  of incorporating source  characteristics
that must be  ultimately  included in model  applications,  such  as
plume buoyancy.   On the  other hand, plume buoyancy  is not directly


related to the  impingement  process, except  as it relates to  the
effective source height and the dimensions of the experiment.  There-
fore, the disadvantages  of  using a real source are  that the source
strength, effective source height, and  source location  with respect to
terrain cannot  be  controlled.

     The use of a tracer allows a greater degree of control and flexi-
bility and may  also be desirable for other reasons (e.g., simplifica-
tion of concentration  measurements).   The tracer source is  therefore
our recommendation.

      The large scale  experiment also  introduces complexities, with
respect to the  structure of the flow in the stable  layer and  the
boundary layer,  that are not present in the small scale experiment.
Characterization of these  flow patterns  may therefore be more

     Without considering the constraints that may  be imposed by
logistical, budgetary,  and measurement  factors,  the large scale exper-
iment probably should not be carried out until the small scale experi-
ment has been  completed.   This would allow for testing of  the basic
concepts involved  in the terrain impingement process and the develop-
ment of parameterization criteria.

     It is recommended that the meteorological data be collected and
summarized (hourly) for  at  least a one-year period at the  site.

     Again, the terrain  features of the large scale  study  should be
selected so that  there is a reasonable frequency with  which  the plume
centerline will impinge  directly on the terrain  feature.  This may
postpone experiments on  very large two-dimensinal terrain features
(ridges) until  comprehensive studies of large hills are completed.


     It is most important that  the sufficient funds  be allocated to
insure that the experimental work and  the  model development  are
evaluated fully after  they  are  completed.

5.1   Matrix of Tests

     A matrix  of  meteorological, source, and  receptor conditions
should be chosen to be  sure  that  the processes are described  adequate-
ly.  For example, in the  small scale experiment, one might decide upon
a minimum of three wind speed groups, three delta-temperature classes,
three source heights,  and two approach angles.


5.2  Repetitive Tests

     Within each box of the matrix one would want more  than one field
test in order to establish confidence  limits of the result.  It is our
opinion that approximately  six to ten tests in  each  box would  be

5.3  Data Retrieval

     It would be very helpful if most of the concentration data could
be reduced and carefully inspected within 24 hours.  This would permit
a quick review  and  increase the efficiency of the test  program.  How-
ever, the key meteorological data and  selected portions  of  the concen-
tration data should be  available in  real time to facilitate handling
of the individual experiments.

5.4  Statistical Analyses

     We recommend that EPA define a minimum set of statistical analy-
ses needed to establish  the adequacy  of the  model  performance.

5.5  Sensitivity Analysis

     The model  resulting  from the study should  be subjected  to a
sensitivity analysis to insure that it will produce reasonable results
over the full range of  intended applications.

5.6  Comparison with Existing Field Data

     While we recognize that there are few sets of field data suitable
for comparison  with the  new (altered) model, a  serious  attempt to
match model predictions  with such data should be attempted.

5.7  Independent Evaluation

     Because of the complexity of both the problem and  the experi-
ments, we recommend that  EPA arrange for an independent, concurrent
review and evaluation of  the program.  We  do not  mean quality
assurance of the data,  for  that is a separate problem,  but rather,
review of the overall  technical quality of the  program.

5.8  Data

     In conjunction with (5.7) it is most important  that the entire
set of field data be taken, reduced, and described in such a way as
to permit independent  evaluation.



     The contractor should  prepare a technical  document which fully
describes the experiment, the  data,  and the model development.   In
the interests of assuring proper use of any model,  it is also neces-
sary to list limitations, special conditions, and confidence bands
for those using the model.

     Because this study  is  designed specifically to define plume
impingement on elevated  terrain, the results may not be applicable
or transferable to all complex terrain situations.  Therefore,  the
degree of flexibility in the model application  should be described.
Flexibility in the model use is dependent on the skill of the user
in relating the measured flow  patterns to the wind tunnel and tank
studies and in extrapolating the results to other source-terrain

     Potential limitations  are:

     A.  Near-field application, approximately one  hour travel time.

     B.  A source-terrain conf igurataion similar to that upon which
         the model is based.

     C.  Restriction to  those meteorological conditions which existed
         during the tests.

     The input data developed by the user must be compatible with the
model requirements.  These  data cannot be specified until the final
stages of model documentation,  but it seems clear that certain
measurements will be required  regardless of the type of model that
evolves.  These are:

     A.  Onsite measurements of wind speed, direction, and stability
         in the layers that affect plume transport and dispersion.
         These data must be consistent with the averaging  time  of
         the model.

     B.  Necessary meteorological and source input data which will
         permit the user to convert from the model averaging period
         to longer-term averages for direct comparison with regulatory

     C.  Emission parameters.

     D.  Definition of the  terrain.


     The funding  required  for even the "minimal" requirements cited
above will be beyond  the  financial capabilities of  some applicants.
Such applicants should  be  guided as  to the acceptability of meteoro-
logical data from beyond  the environs of the pollutant source.   A
first step toward such  guidelines could evolve  from a study of the
applicability of  the  experimental data obtained at various sites
during the field  tests.   The support document for  such guidelines
should include discussion  of the degradation of model  results  in
terms of the degradation  of  the input data.


7.1  Non-Impingement  Maximums

     The maximum  three-hour  concentrations in complex terrain often
are not associi ted with the  direct impingement  of  stable plumes on
high terrain obstacles.   Rather, the maximum values are frequently
found during transitional  periods when the stable plumes are brought
close to valley walls by  thermally-induced circulations generated by
unequal heating and cooling of major  terrain features.  Such phenome-
non may occur, for example,  when the western wall  of a  valley  is
heated by the sun  in the early morning while the eastern wall is still
in the shadow; a  cross-valley circulation develops,  causing a transi-
tory fumigation situation.

     Another situation  which should not be ignored  is the extremely
persistent moderate to  strong wind neutral condition. This situation
may be more important than the stable case  in  producing 24-hour
maximum values in some  configurations.

     We recommend that  EPA investigate these phenomena, using the
experimental data generated in  this project,  as well  as other
available records.

7.2  Relation to  National  Air Quality Standards

     Even after completion of these studies, few of our panel members
expect the predictions of the highest  second-highest concentrations at
locations different from the test sites to be accurate within a factor
of two.  Factors  of three  to ten are more likely.

     An important reason  for this large uncertainty factor is that
the meteorologists are  being asked to predict an extreme value in
the probability distribution of concentrations.   As Lamb points out
in his written comments on this program, the highest second-highest
concentration is  extremely difficult  to predict.   Grey, in his letter


to Hovind dated June 22, 1979, also  recognizes  this problem,  but
neither he nor Lamb suggests one obvious solution; the meteorologists
could very well insist that the quantity which  they are asked  to pre-
dict be a reasonable one.

     The highest second-highest concentration is  an administrative
choice reflecting the idea  that there are certain maximum concentra-
tion levels below which health and welfare effects are insignificant.
These same maximums could easily be achieved in most cases by relat-
ing them to a reference concentration in the probability distribution
nhich occurs much more frequently  than the highest second-highest
value.  A more predictable  quantity  would make  our regulatory de-
cisions less capricious.   It  makes  little sense to insist that the
emission limitation for an  industrial  plant be  twice as stringent
if based on one set of five-year meteorological  records than it
would be if based on a different five-year set.   As one member of
our panel asked:  "If the predicted  3-hour highest second-highest
S02 concentration for a given plant  is 1,420   g/m  (-10% over the
1,300  g/m  standard) and  the accuracy of the prediction cannot be
specified to better than a  factor  of five, should we deny him a
permit, or require 50 million dollars  worth of  control equipment?"

     The field data needed  to readjust the definition of the stand-
ards, without changing the  desired  maximum levels, exists.   Ju-
dicious use of it would permit us  to employ  a much more orderly
system, based on more predictable values.   This  does  not imply
abandoning the intent of the  existing  standards,  such as allowing
only rare exceedances of 1,300 and  365  g/m   SCX, concentrations for
the 3-hour and 24-hour averaging periods, but  rather, achieving them
in a better way.

     This question is, in a sense, beyond the scope of this Workshop,
but it is not beyond the consideration of the accuracy of complex
terrain (or any other) model.

                   3.   EXPERIMENTAL DESIGN PANEL

                     PANEL LEADER:  Gene Start


     Shep Burton                        Frank Schiermeier
     Warren Johnson                     Tim Spangler
     Ron Lantz                          Dean Wilson
     G. DeMarrais                       Mike Williams
     Fran Pooler                        William Wilson


1.1  Introduction

     A goal of this Workshop is the identification and selection of an
important and tractable aspect of the behavior of airborne effluents
within the setting of  complex terrain.  The  primary focal  point
selected for investigation is the concept of plume  impaction upon
elevated terrain.  Plume impaction is the behavior of a plume as it
encounters the terrain.  Emphasis is directed toward understanding
this phenomenon for plumes  which are emitted well above the ground and
which interact with  higher terrain at  downwind locations.   Uncertain-
ties exist regarding which phenomena are significantly contributing
to the plume/terrain interaction and what magnitude of effect will
result from the action  of these phenomena.  There are several possible
features of the topographical setting  and on-going physical processes
which may be important contributors to the cumulative behavior which
is termed "impaction".  Certain broad categories of terrain  and
meteorology may be considered and the experimental focus may  be
selectively reduced  to include a subset of them.   This subset may be
examined more thoroughly than the full set.  The  qualitative  and
quantitative understanding developed from the subset would provide
sound guidance for understanding these  selected conditions and perhaps
guide related modeling for the remaining situations not investigated.

     It is desirable  to investigate impaction as a function of terrain
types.  Four types of terrain have been identified and ranked in order


of expected complexity.   They are  1) isolated hill,  2) ridge  line,
3) broad valley,  and  4)  canyon.  The isolated hill appears to be  the
simplest, most  easily understood topography and the study of  it is
recommended to  be first.   It also is the easiest to compare to con-
current wind  tunnel  and water tank simulations.  Subsequent studies
should consider the other  topography once understanding (some of  which
should be transferable) is developed for hills.

     Impaction  needs to be studied as  a function of meteorology.
Three atmospheric stability  situations are considered most important;
stable, neutral,  and transitional from stable to neutral conditions.
Unstable stabilities should also be investigated, but stable flow is
the selected  focus of this Workshop due to  its greater importance in
current modeling  evaluations.  Neutral  cases  also have significant
potential for impaction of high concentrations  on elevated terrain.
Such impacts  have been observed and  documented.

     The transitional period from stable to neutral flow is included
because it presents a potential for mixing very high concentrations to
the surface of elevated terrain.  Studies of  plumes originating during
stable conditions,  with airflows over  elevated  terrain, may include
impaction during  transitional periods  (either a diurnal change or a
turbulent episode)  and thereby provide  insight  on other features of
the impaction process.

     The evaluation of plume impaction upon complex terrain must  in-
clude many considerations in order to achieve probable success.  The
experiment must include surface and  upwind aerial measurements of
tracer concentrations.  Central to the experimental design is the need
to discern how  the tracer concentrations measured on the terrain
slopes compare  to the aerial tracer  concentration which would have
existed at the point in space were there no topographic features.  The
essential ideas are summarized in Figure 5. Several observations of
plume centerline  concentration must be collected at distances upwind
of the terrain  in order to unambiguously specify the magnitude of
tracer concentration and the rate of change of  concentration with
downwind distance.   These observations  must yield an extrapolation
(or projection) of expected aerial concentration for the distance of
the elevated  terrain.  A corresponding observation of tracer concen-
tration on the  slope is measured.  The ratio of  observed to expected
(extrapolated)  concentration is termed the impaction ratio.  If  the
ratio equals  one, the terrain obstacle presents no detectable altera-
tion of plume concentration and complete or full-value plume impaction
has occured;  if the ratio equals 0.1 the impacting plume concentration
is only 1/10  of expectations and some diluting or resisting mechanism
has reduced the magnitude  of  the plume  impaction.   It is  very


important  that the same averaging  times  be used  for all  tracer
concentration prior to ratioing them.
                                       Slope measured concentration
                                       Measured concentrations
                               	H  Extrapolated concentrations

                                    = Distance of topographic feature.
Figure 5.   Estimation of ambient  plume behavior  and  the degree of
impact ion  upon elevated terrain.
     If  the  ratio differs significantly  from unity, then more detailed
measurements of magnitudes  and  profiles of micrometeorological  and
tracer concentrations would be  useful  to understand the near terrain
slope processes which alter these plume impactions.  Figure 6 sche-
matically  depicts a possible observed near-slope  profile of tracer
concentration and an extrapolated profile of tracer based upon upwind
measurements.   A divergence of these  profiles from one another is  de-
picted.  Two hypotheses for the differences in concentration profiles
are the  following.   The average observed tracer concentration values
(and therefore the profiles) are less  than expected because of topo-
graphically  induced transport and/or diffusion effects.  These time
integrated (averaged) concentrations  could be less,  due to the tracer
samples  being collected during  alternating periods with full-value
and reduced-value (or even  tracer free air) concentrations.  Under
this situation, the tracer  concentrations in time integrated samples
collected  on the slopes would be less than the  extrapolated tracer
concentrations; but the area of coverage on the slopes could be larger
than expected from extrapolations of the plume cross-sectional area

determined  at upwind points  of observation  if  enhanced meandering of
the plume  centerline occurs  near the topography.  Another manner in
which  smaller concentrations might be sampled on the terrain could be
the result  of the slope  boundary layer  (when it exists).  The micro-
meteorological processes operative within the slope boundary layer may
either produce additional  tracer dilution  or  impede the transfer of
plume  mass  through the  layer.   In either case the time-integrated
tracer concentration would be reduced in the terrain samples.  In all
likelihood, the magnitudes of  plume impactions upon elevated terrain
are the result of all of  the above processes  acting together.  The
dominance  of one or more  phenomena  (or  the subordination of others)
probably accounts for the widely differing observed plume impaction
and postulated behaviors.  The meteorological and topographic factors
and their  magnitudes, which lead to the  dominance or subordination of
certain phenomena related to wind direction meandering, turbulence,
and diffusion, are key  relationships to investigate.
                                 — Q  Extrapolated concentrations
                                 	•  Near slope concentrations
                                  Xj= Distance of topographic feature
Figure  6.   Schematic  depiction of near  terrain profiles  of  tracer
      To concurrently  evaluate and improve the performance of models,
many  factors must be measured.  Transport of the airborne plume may be

a highly important  factor and it is recommended that winds  be deter-
mined in the  form of  a multilevel field of u,  v,  w wind speed com-
ponents.   The dispersive  power of the atmosphere should be parameter-
ized for each  test  through the measurements  of  turbulence, ambient
plume diffusion  and atmospheric stability.   Parameters describing
the tracer sources, such  as its strength,  height  and horizontal
location must  also  be documented.  An effort  to establish the energy
budget  (e.g.,  various turbulent fluxes) might  also be included in the
experimental  measurements.

     The conduct of the experimental  study may be significantly
affected by practical constraints.  The most important constraint
could be the  funding  limits.   The design and budget should be care-
fully prepared to ensure  that the most imporant parameters  are being
included and that the  experiment isn't too limited in scope to provide
sufficient information to obtain meaningful  results.  The design also
must consider  the availability of potential  sites which satisfy the
experimental  requirements.  One type  of idealized measurement site
would have a  power  plant  about 5 km upwind of  an  ellipsoidal  hill
which extends  higher  than the effective plume  height;  transport of
the plume, during stable  flow, would  occur toward the hill 365 days
per year.  It  is doubtful that such a  site exists.  Therefore, the
experimental  design must  consider availability of sites early in the
design process.

     The experimental design must consider the  timeliness and the
applicability of  the results.  Some findings  (significant information)
should be provided after a reasonably short period of time in order to
demonstrate the  desirability of continued  funding of this program.
The information acquired must be applicable to  the real world and have
direct relevance to the engineering design and  regulatory problems
of plant settings within  complex terrain.   The selection of a "full-
scale" setting (typical of a number of operating fossil-fueled power
plants and/or  smelter plants) should  be considered.

     A real concern is the risk of developing erroneous conclusions
due to an inadvertent (and unknowing) subordination of  certain
physical processes.   These physical processes, because of the selec-
tion of smaller  than  typical settings  and  topographic features, may
have an inordinately  small relative contribution to the overall com-
bined effect  by  the full  spectrum of  transport and diffusion mecha-
nisms.  If the relative contribution of a phenomenon to the transport-
ing and/or diffusion  of an airborne effluent is scale dependent, then
conclusions based upon observations at a small hill may not  translate
to conclusions for  a  large hill, etc.  For example, the presence or
absence and size or magnitude of the  effects of  slope flows  and


slope boundary layers are  believed to depend upon terrain obstacle
size.  The ultimate transfer  of  airborne material to the terrain
obstacle surface  (plume impaction) can be significantly altered by the
strength and size of slope boundary layers and flows.  If a choice of
scale for the field study  excludes or subordinates these phenomena,
there is a distinct risk  that inapplicable conclusions (and formu-
lated models) would be applied to larger settings in which these
phenomena would contribute significantly.  On the other  hand,  in-
vestigations of a specific setting will increase understanding of
that scale; a second investigation of a substantially different scale
will provide additional understanding.   There may be partial agree-
ment between study findings and some distinctly different and perhaps
conflicting findings for studies of very different size of topographic

     Some other constraints will be in the areas of instrumentation
and expertise to handle the job.  The measurement and design panels
jointly attempt to avoid  the  development of a plan for which no ade-
quate and proven instrumentation or methodology exists, or whose im-
plementation would be prohibitively  expensive.  Similarly,  the
availability of  qualified contractors must be considered when
establishing a time table  for the experiment.  (They may already be
committed to another activity).

     From an advancement  of science perspective, it seems desirable
to study the simple geometry and setting to gain a clear understanding
of the observed plume behaviors.  This understanding may be a trans-
ferable module which is incorporated (largely intact) into either more
generalized models to be  developed or used as a module for adjusting
some of the existing models to plume transport, diffusion, and impact.
Once an initial understanding is achieved, the  more difficult  and
diverse settings and processes may be examined  through  module by
module systematic investigations, as necessary.

     The advantages and disadvantages of three  scales  of complex
terrain plume studies were considered.   The  scales are  (1) small
(50 to 100 m high) hill study,  (2) power plant  scale plume study,
and  (3) large scale (400-600 m high)  hill  study.  Preliminary
scenarios for scales  (1)  and  (2) are contained  in Appendix A.   A
summary of strengths and  weaknesses for each scale of study follows.

     3.1.1  Small Scale  (50 to 100 m) Hill Study

              •  Advantages.   Source mobility is a decided advantage
over a fixed source in guaranteeing plume  impaction of the hill under

study.  The  logistics  of  conducting such a small scale tracer study
are decidedly easier  than either of the two  larger  scale studies.

     Because of  the small scale, this study has a closer relationship
to laboratory or physical plume modeling.  The relatively low plume
heights would permit  experiments to be conducted in the most stable
regimes which occur close to the ground surface.

            *  Disadvantages.  The small scale of  this study poses
several measurement problems (for example, plumes are of  small size
and travel  distances  are  relatively short) because  measurements of
particulate  plumes by  lidar would be approaching or decreasing below
the lower limits of  resolution.  To alleviate this problem it has been
proposed to  develop an initial volumetric source or to relocate the
source farther  upwind.  This tradeoff may permit improved lidar reso-
lution, but  would increase the difficulty of aiming (impacting) the
plume on the small hill target; the releasing of tracer with a  virtual
size would  also  be more difficult.

     Even if lidar measurements of the particulate  (e.g., oil fog)
plume were  made  possible  by this adjustment, the  determination of
absolute concentrations of plume tracer remains a difficult problem.
Airborne detection systems for tracer  concentrations would  be in-
effective in measuring axial values due to the small vertical extent
of the plume.   Also,  aerial sampling may significantly affect the
small plumes by  the additional  turbulence  due to  the aircraft.
Balloon-borne measurement packages may yield vertical plume dimen-
sions but appear to be unworkable due  to a likelihood of  horizontal
positioning  errors.

     The preliminary  proposal (Snyder, Appendix A) using  five 150 m
instrumented towers,  is believed to be  too costly.   When these costs
are combined with other direct study expenditures, they are estimated
to about 75% of  the $3.3  million tentatively allotted for the field
experiments.  A subsequent proposal to reduce the tower requirement to
one 100 m tower  eliminates the  cost problem,  but  significantly
cripples the information  content of the  small scale study.  To sample
the low-level wind fields  near the obstruction, it may be necessary to
revert to low resolution pibals since remote sensors such as acoustic
dopplers cannot  measure within the initial  30  to 60 m above  the

     Finally, the appropriateness of the scaling of the small scale
study to the real world situation can be  a problem.  Phenomena  such as
wind shears, strengths of the  boundary  layer,  and the size  of
mechanical/convective  eddies are necessarily different between the


proposed small scale  and the larger scale in which power plant plumes
         *  Conclusion.   The panel feels that the small scale hill
study consists of many  valuable experimental concepts, but that the
scale is probably too  small to be workable, clearly representative, or
of immediate applicability.  Therefore, these concepts have been em-
bodied into a large scale hill study.

     3.1.2  Power Plant  Scale Plume Study

         •  Conclusion.   Without describing the advantages and
disadvantages, this option was passed over because of its dependence
on power plant emissions  from a fixed source location.  The occurrence
of useful test days in  which the wind transport was acceptable might
be rare.  The funding for the field experiments  is too  limited to
allow success to be  dependent on the vagaries of transport wind direc-
tion and plant operational characteristics.  Ideally, this scale of
field study would reflect the real world, but it  is not affordable
at the anticipated  funding level and no suitably situated plant has
yet been identified.

     3.1.3  Large Scale  (about 400-600 m) Hill Study

         •  Advantages.   The basic premise  of  this tracer study
is to incorporate the source mobility of the small scale hill study,
but project it toward a  larger terrain obstacle in an attempt to fa-
cilitate supporting measurements.  For example,  the upwind fetch is
sufficient to permit  definitive transport and diffusion measurements
of the combined tracer/particulate plume by airborne lidar and tracer-
sampling aircraft.  Similarly, the plume elevation is sufficient to
permit definitive measurements of the plume structure, the boundary
layer and the low-level wind fields by remote sensing techniques  such
as ground-based  lidar and acoustic doppler sytems.

     More important is  the closeness of this scale to  real-world
situations and the  minimizing of concern regarding scale subordina-
tion of phenomena affected by wind shear, boundary layer existence and
structure, and turbulent diffusivity.  This resemblance to  actual
power plant plume situations and dispersion provides for more imme-
diate applicability of  results, and an immediate credibility to
non-technical and non-meteorologist recipients.

            •  Disadvantages.   Because of the increased scale,  the
large scale hill study  necessarily entails more logistical diffi-
culties in some ways  (but  possibly less in others). Although achiev-
able, this study would  require  more personnel, aircraft platforms,
remote sensors, and increased source strength.   These additions  not
withstanding, the  large-scale hill study (field experiment) would
cost about half as much to the  same as the costs for the small  scale
hill study (as originally  proposed).

            •  Conclusions.   It is recommended that at  least  two
large-scale hill studies be conducted in the complex terrain setting.
For reasons cited  above, this approach is deemed most cost effective,
more acceptable and representative, and would produce  results of
immediate applicability.   The conduct of the necessary measurements
appears feasible   with  existing measurement technology.

     The small-scale  hill  study is believed to exceed (or extend to
the very limits) the  resolution capabilities of most remote and air-
borne measurement  systems.  Fixed in-situ measurement techniques  are
possible but the costs  of  these measurement arrays to  define  the
meteorology and the plume diffusion adequately are believed to exceed
greatly the costs  for the  large hill measurement configurations.

3.2  Design Concepts  for Plume/Terrain Interaction Study

     To examine the interaction between airborne effluent plumes  and
elevated terrain near effective plume height, a setting is desired
with the height of the  topography comparable to or greater than  typi-
cal plume heights  associated with fossil fueled power plants during
stable conditions  in  the Western United States (to avoid controversy
regarding scale size).  The experimental design will be discussed from
the perspective of the  400-600  m hill.

     The work required  for this study can be conveniently separated
into components associated with site selection, frequency and duration
of experiments, and the measurements which must be made in character-
istic zones of pollutant behavior.

     3.2.1  Site Survey and Selection.  An  initial task  will  be
selection of an appropriate site  or sites which optimize the chance of
useful information within  budget, time,  and  design constraints.
The design constraints include  a  400 to 600  m hill  reasonably
isolated from major terrain influences by fetches of  relatively
flat land.  In this context,  releases may be made at distances of
up to 5-10 km from the  base of  the hill; tracer releases should

be initiated at  locations free of wake effects  from other terrain
roughness  influences.

     The hill  should also be relatively  symmetrical (circular to
elliptical). For circular  symmetry, releases  may be made from a  number
of directions  without changing the cross-sectional shape of the
terrain; for elliptical symmetry the contribution of aspect ratio
might be considered.  The intent of the circular  symmetry constraints
is to provide  many  similar stable flow experiments with features as
consistent as possible during study periods.  Some  of these constraints
on symmetry of  the  hill could be relaxed if certain wind direc-
tions are  precluded because of inappropriate upwind terrain. Also, if
crosswind  shape  variation does not significantly detract  from the
measurements or  does not diminish the number of acceptable testing
days which occur, or if aspect ratio does  not significantly detract
from the measurements or does not diminish the  number of acceptable
testing days which  occur, or if aspect ratio variations are desired,
hill symmetry  becomes less important.

     An important  consideration, although  not essential, would be the
possibility that a  given site (hill) may  be situated within a region
of channeled flow  so that the frequency of  acceptable testing condi-
tions is greatly increased along certain preferred wind directions.
Then the logistics  could be greatly simplified  because appropriate
source release points and fixed measurement sites  would be much easier
to locate, and more permanent.

     3.2.2 Frequency and Duration of Experiments.  An important re-
quirement  of the site is a high frequency of stable flow with depths
up to and  exceeding the height of the hill.

     A goal is to achieve 50 stable flow experiments (total) during
conditions of stable flow over two periods  of testing. Each experiment
should include at  least 3 hours of tracer releases and measurements,
and 6 hours is suggested as a usual duration. (Impaction contributions
to the 3 hour air quality standard are to be considered).  The experi-
mental periods would cover two or more seasons  of the year  during
which stable conditions are expected. A  relatively large number of
experiments is required in order to provide information on the details
of plume interaction with high terrain considering  variations of wind
speed, temperature  gradient, height of release, and time of day. In
the case of time of day, nighttime and morning cases may be of special
interest.  Morning  cases are important.  Field experience indicates
that the occurrence of high concentrations upon elevated terrain is

frequently  associated with plumes established during stable condi-
tions which are  transported toward  obstacles during daytime condi-
tions.  Nighttime cases are representative of the highest frequency of
stable conditions.  In order for a site to be acceptable, an examina-
tion of the local  climatology  should suggest an occurrence of a large
number of days with acceptable stable  flow (exceed 30) over an ex-
perimental  season  or period  (in  which about  20 to 25  tests  are
     Once an individual experiment has been initiated  (for an expected
6 hours of  continued measurements),  there is no assurance that the
atmospheric stability and flow condition will persist throughout the
experiment.  In this event,  the  experiment should,  in general, continue
since important  transient behaviors  and understanding  of peak  to
average concentration fluctuations may be documented.

     3.2.3   Characteristic Zones.  It  is convenient to describe the
experimental measurements from  a concept of charateristic zones within
which certain  activities and changes in turbulent diffusion and plume
transport are  expected. Four  zones are identified and are shown in
Figure 7.   Zone  1  contains the release of the tracer plume (and its
plume rise,  stabilizations, etc., if applicable).  Zone 2 is the trans-
port zone.  Within Zone 2 the tracer plume is transported and diffused
by usual atmospheric conditions (those conditions not incorporating
topographical distortions of flow streamlines or alterations of turbu-
lence).  The "ambient" behavior of the plume is established in this
zone.  Zone 3  contains the terrain feature of interest.  This terrain
feature is  instrumented to measure possible plume impaction upon the
slopes; airflow  distortions,   changes  in atmospheric turbulence, and
differing rates  of diffusion  developed here. Zone 4 is the  region
"downwind"  of  the  terrain feature.   Within the wake zone the tracer
plume continues to be transported and diffused in manners which differ
from tne ambient conditions of Zone 2.  However, at  longer distances
downwind, Zone 4 transport and diffusion characteristics converge to-
ward the Zone  2  ambient conditions.  Each of the characteristic zones
and the measurements to be performed are described in greater detail
in following paragraphs.

  Zone 1. Tracer source (plume stabilization, etc. as appropriate).
  Zone 2. "Ambient" transport and diffusion during approach to elevated terrain.
  Zone 3. Plume interaction/impection with elevated terrain.
  Zone 4. Downwind wake transport/diffusion/impact and return toward ambient conditions.
Figure  7.   Conceptual  depiction of  characteristic  zones of tracer
plume transport and diffusion.

            •  Source  Zone (1).  The principal activities required in
the source zone are the release of  gaseous tracer and a particulate
tracer.   The particulate  tracer should be suitable for providing flow
visualization (probably via airborne lidar) at distances beyond 5 to
10 kilometers.  The release platform for the particulate and gaseous
tracers  must be  semi-mobile, with capacity for six to seven hour dura-
tion of  tracer release.  The source height should be adjustable so the
plume height can be varied from about  half-hill  height to a modest
amount  higher than the hill top.  The  horizontal  location of  the
source  should be semi-mobile  (unless  the ideal site was found) so
that it  may be easily  positioned directly upwind of the hill before
the experiment is begun.   Once  the experiment is begun the source will
be fixed for the full  test period  (6  hours).  The effective initial
size of  the plume shall be on  the order of 30 to 50 m in the vertical
and 75  m in width.  These minimum dimensions ensure that known plume
sampling methodology  may  be effectively utilized  to define plume
spread  statistics, concentrations,  and spatial locations within Zone
2 prior  to interaction with the elevated terrain.  Particulate tracer
and gaseous tracer plumes must be coincident downwind of the release

     The use of  multiple release points  for pairs  of separately
identifiable particulate and gaseous tracers  could  provide greater
assurance that a successful test was achieved during each attempt.
A method of distinguishing between the various particulate releases
might be required so that flow visualization  advantages could  still
be retained.

            •  Transport  Zone (2).  This  zone  of meteorological trans-
port and turbulent diffusion is of nearly equal  importance to the
actual high terrain zone of plume influence (Zone 3).  Within this
zone the atmospheric rate of diffusion,  which determines the  upper
limit magnitude  of plume concentration which  potentially may  reach
the slopes, is operative.  Since neither this rate of diffusion nor
the absolute concentration can be predicted  with precision,  the con-
centration  at a  number of successive downwind distances  must  be
measured; uncertainties  in the absolute  concentrations will translate
directly into uncertainties in the degree  of impaction  of  plume
centerline  concentration.

     Documentation of plume transport winds and  the observed tra-
jectories will yield insight regarding peak to  average tracer concen-
tration statistics and the frequency of occurrence of transport to the
terrain object in question.  It is very  important that the measure-
ments in Zone 2 are sufficiently numerous so that the details of  plume
dilution can be  defined  before the terrain begins to perturb the flow
and plume concentration.   Otherwise, it will be  impossible to estabish
what additional  dilution results from terrain interactions.  In  addi-
tion, measurements within Zone 2 will be related to long-term on-site
measurements in  order to define the frequency  of terrain interaction
in a climatological sense.

     There  are two major types of information  to be observed in Zone
2: (1) plume characteristics and (2) meteorological characteristics.
Plume characteristics will be defined in  two ways.  First, the spatial
distribution of  the particulate tracer will be examined by airborne
and ground-based lidars.  The airborne lidar will provide  cross-
sections of the  plume at various distances downwind from the source.
These measurements will  extend into Zone 3,  and  possibly  farther
downwind.   The airborne  lidar system would  provide  plume transport
depictions  and structure in this zone and in  Zones 3 and 4 as  well.
The ground  based lidar will provide multiple  planes of observation of
the plume in a nearly instantaneous sense. A pooling of these obser-
vations will yield averaged time histories  of  concentration (relative)
and plume spreading statistics.  A minimum of  two, and preferably 3 to
5 planes (lateral-vertical) of observation  are  needed.

     In addition  to  the particulate tracer observations,  an airborne
system must sample the nearly instantaneous plume centerline maximum
concentration of  the gaseous tracer by traverses through the plume.
These samples must be at locations which correspond to the cross-
sections of particulate tracer observations so that the particulate
plume (which may  be  averaged in time) becomes  "calibrated" to the
gaseous tracer  concentrations.

     For meteorological characteristics,  three major measurement ob-
jectives are determination of the wind field  (u,  v, w) at various
heights, determination of the vertical  stability, and measurement of
the atmospheric turbulence at various points upwind of the terrain
obstacle.  The  wind  field could be determined by a doppler acoustic
sounder, or by  a  lidar device, or by tethersonde measurements.  The
acoustic sounder might have to be somewhat  mobile to be locatable into
the approximate upwind sector before the beginning of each day of
experiments.  Vertical stability could  be obtained from the tempera-
ture profiles provided by an aircraft, tethersonde, or minisonde.
In addition, a  specially instrumented aircraft would provide detailed
measurements of turbulence at various points.

     All of these aircraft would also make measurements in Zone 3
approximately near the terrain, and possibly in Zone 4.  The doppler
acoustic sounder  could continue to make  measurements over the pro-
gram study period in order to define the  frequency of occurrence and
duration of plume transport  conditions believed favorable for terrain

            •  Interaction Zone (3).  Zone 3 encompasses that area
starting upwind of the hill where significant  distortions of flow
streamlines are thought to begin.  It extends downwind from the ob-
stacle an imprecise  distance (perhaps at the downwind extent  of the
base of the hill  or  to a few height increments farther).  Zone  3 then
indistinctly blends  into Zone 4.

     The plume effluents transported through Zone 2 toward the terrain
may experience a number of possible special phenomena.  The end  result
of the joint action  of these phenomena may be postulated to be any-
thing, varying from no plume  mass impaction upon the elevated terrain,
complete impaction of the maximum possible value of plume concentra-
tion, or something in between these extremes.  The problem is further
complicated by  the need to know the temporal  behavior  of  what is
little understood in the first place.  The flow distortions effects
within the interaction zone must be examined  to parameterize their
contributions to  the variability of concentrations which may  be ob-
served at the terrain surface.  These variabilities should be related


to meteorological conditions.  The resistance (or conductivity) of the
slope boundary  layer to mass fluxes of  airborne (Zone 2)  effluent to
the slope  surface  must also be investigated;  it  probably is scale

              Plume Characterizations.  The transport  and diffusion
characteristics  in the slope boundary  layer may be critical to con-
siderations  (and understanding) of the plume  impaction process.
Requirements  for plume measurements in this setting (all of Zone 3)
include measurements of  maximum tracer concentrations reaching within
1 or 2 meters of the terrain surface (sequential  60 min. average
values at  about  100 locations,  plus sequential 10 min.  averages at
about 10 of  these  locations).  Several  (perhaps 5 to 10) short towers
(on the order ox 10 meters) could be placed at selected sampling posi-
tions to describe  the change of tracer concentration with  height.  As
an initial estimate of the spacing of  samplers upon the elevated ter-
rain, the  following type of  guideline  is presented.

     a)  Horizontal spacing:  determined from expected  plume width
         parameter at the downwind end of Zone 2,  e.g., about 0.5
         to  0.8  ov .

     b)  Vertical  spacing:   determine  from expected plume thickness
         parameter,  in a manner corresponding to  ay , about 0.5 to
         0.8 ' az.

     c)  Samples need not cover the entire hill.   A band or capping
         array  could be  used, as appropriate to the controlled height
         of plume  relative  to the terrain.

Up- and downwind sides of the hill should be  instrumented.   Near-
surface profiles of concentrations should be obtained from 2 or more
tracer samplers  located  on  the few short towers  installed on  the
slopes.  The  cumulative  sampling period for gaseous tracer should be
consistent with  the postulated six hour tracer release  durations.
Several 3  hour  averages  may  be calculated from the six one hour se-
quential samplings within each individual 6 hour  test.

              Meteorological Characterizations.    Meteorological
measurements  in  Zone 3 are needed to define the wind field at several
heights and  positions about and above  the hill.  In a similar manner,
temperatures  should be measured to specify the thermal  stability.

     A tower  should be located on top  of the hill.  Measurements of
the gaseous tracer  concentration profile  and 3 or more levels of u, v,
w, and temperature,  plus turbulence parameters,  should be collected


during the experiments.  Wind  and  temperature  sensors (at 2 levels)
should be placed and operated  on several  of the short (10 m)  towers
located upon the terrain slopes.   The acquisition of turbulence data
at these towers on the slopes could provide additional information of
importance.  If Gaussian formulations are unsuccessful, profile data
might assist in the development of gradient or K-theory models of
turbulent diffusive transfer within  the slope boundary  layers.

     Some portion of the field site meteorological data should be
available to be examined in  near-real time (e.g. , 2 minute averages
updated every minute or two)  to assist in quality assurance and guid-
ance of the test preparations  and  conduct.
            •  Wake  Zone  (4).   The zone downwind of the terrain ob-
stacle tends to lie  outside the primary area of interest.  However,  if
several indirect and mobile  sensing systems are utilized in the con-
duct of the experiment,  or if atmospheric conditions  change the
behavior of the plume  and  local  meteorological parameters,  many
potentially interesting and variable observations of  opportunity  could
be easily collected.   These  data would either supplement on-going
programmed measurements  or substitute for those which would not  be
taken due to a departure  from test window conditions.  Measurements  in
this zone would be  similar to the data collections in Zone 2.  Air-
borne lidar observations  of the particulate plume would be of signifi-
cant value to show  trajectories  and  wake diffusion downwind of the
hill.  Aircraft turbulence,  wind, and temperature measurements  could
greatly increase the understanding of transport and  diffusion in this
zone (at least relative  to the upwind Zones 1, 2,  and 3).

     3.2.4.  Long Term On-Site Documentation.  For the complex
terrain situation,  it  is desirable  to have  an understanding  of
climatology of flows,  stabilities,  and perhaps other  parameters
that control whether an  elevated plume will cause  high ground-level
concentration on a  hillside.   It is  necessary to  determine, for
various time averaging periods, the frequency at which concentrations
occur within twenty-four hour periods and for periods extending out
to the entire year  (second-highest  concept).

     It is also important  that we know what other kind of  terrain
induced flow and turbulence  phenomena might  be occurring  in the
area, but which were not observed during the study period.

     Therefore, it  is  important  to continue some of the more routine
measurements at the study  site for  some additional time,  perhaps
a year, before and/or  after  the  conclusion of the intensive  field


experiment(s).   The most important  parameters  to  continue measuring
may be winds,  as a function of height,  and the vertical stability.
An acoustic  sounder system(s) might fulfill these needs  for wind
and vertical  extent of turbulent mixing or its layered structure.

     3.2.5   Additional Experimental Considerations.  Prior to final
experimental design and the  physical  setup of a field measurement site
(and perhaps  before final selection of  that site) several screening
studies could  be performed.  These  screening studies should suggest
appropriate sampling resolution (temporal and spatial) and some of the
more important physical phenomena to be quantitatively measured.  The
following  examples of screening studies may be valuable before de-
velopment  of the final field study design.  Monitoring data from sites
surrounding  sources of opportunity  should be screened.  If the tem-
poral resolution of the plume(s) of opportunity is on the order of
minutes to an hour or two, meaningful guidance may be gained regarding
peak to average effluent concentrations with some implications for
controlled tracer sampling equipment.

     Turbulence measurements previously collected within complex ter-
rain settings  should be reviewed for insight about  expected phenomena
and their  aproximate quantitative values.  Recently, turbulence
measurements  have been collected by researchers to describe the air-
flow environment for wind energy systems which might be located on the
top of ridges  and hills.  These data should be studied.

     A number of preliminary visual tracer studies should be conducted
on and around  the candidate field study sites.   Some knowledge of the
size and strength of terrain slope boundary layers and airflows may be
gained.  In  this way, the bias due  to selection of a particular size
of terrain feature (scale related subordination of some phenomena) may
be quantitatively revealed.

     Finally,  physical modeling of  the  selected site may  provide
valuable insight for the final experimental layout of measurement
devices.   Focal points for  measurements (characteristic spatial loca-
tions on and  about the hill) may also be suggested.

     Another  approach to the conduct of this plume  impaction study is
the separation  of the investigations  into two component parts,  each of
which is conducted somewhat separately.   (To some extent, the small
hill (50 to  100 m) study may be an  evaluation of impaction behaviors
without the  likelihood of significant influences from slope boundary
layers and flows).  The phenomena which govern the impaction process
may be separated into phenomena which occur either near the terrain
(within the  slope boundary  layer and flows) or not near the elevated


terrain.  Investigation of plume mass transfers  through the slope
boundary layer would be expected to be site and site-scale specific;
measurements  for  several different settings  would be required with
detailed, fine-resolution measurements.   These  measurements would des-
cribe the micrometeorological behaviors within  the slope boundary
layer; the plume  mass fluxes through this  layer would be analogous to
a plume deposition  study (usually conducted  above flat, simple sur-
faces).  The  second component of investigation would study the trans-
port and diffusion  of airborne  effluent  to the  point  of  either
impacting upon the  terrain (if no significant boundary layer exists)
or to the point of  increasing influence of the slope boundary layer
processes.  This  second component of  the  study  relates to the site
climatology of transport and diffusion in  the  general vicinity of the
topography; it describes the concentration of plume effluent,  the
frequency of  its occurrence, and its spatial location. It is analogous
to a potential fjr  impaction; the near-slope  component describes the
receptivity of the  slope boundary layer to a  mass flux through it to
the terrain surface receptors.  Both components of the study must be
addressed; this alternate consideration simply  poses the idea that the
overall study might be decomposed into smaller research modules with
fewer specific focal points within each module. With more but smaller
and specific  research modules, the time period for development of an
overall description (model) of plume  behavior  could be  lengthened
unless several modules may be run concurrently  with each  other.

3.3   Summary and Conclusions

     The understanding of impaction of plumes from tall  sources
against topographical feature.s is the primary  goal of this experi-
mental design.  Thermally  stable atmospheric conditions are the focal
point, but neutral  and transitional conditions should also be under-
stood.  In the first stage of experimentation,  a hill  of  simple
geometry and  relatively isolated from other elevated terrain is sug-
gested; it should have a size commensurate  with real sites about power
plants in the western United States.  The essence of the study is  a
combination of meteorological and gaseous tracer measurements which
must satisfy  the following  minimum requirements (at  least as viewed by
this panel) during  a particular field test.

     A set of tracer data  points must be collected which clearly des-
cribes the magnitude and rate of dilution  of the airborne effluent as
it approaches the elevated  terrain.  A projected (expected) concentra-
tion value must be  obtained, for the position  of plume impaction upon
the terrain slope,  were no alterations of  airflow and rate of diffu-
sion to occur before plume impaction.  The  observed concentration

versus the projected  concentration demonstrates the degree of  impac-
tion.  A null  concentration observation indicates no impaction. More
subtle features,  such as the concentration  gradient in the boundary
layer immediately adjoining the slope,  is an  interesting facet  of the
problem and  should clarify the role of  the  micrometeorology  within
the layer relative to the impaction problem.

     Sufficient measurements of the meteorology, transport (visualiza-
tions both of  the plume and slope flows), and  turbulence should be
collected to document the dynamics of  the problem.   Routine site
monitoring measurements should cover a longer period than the  inten-
sive field studies;  these data may help resolve the uncertainty about
what magnitudes  of plume concentration  impact for  longer period

     Finally, pre-field test physical modeling simulations may guide a
final design of  the field installation.  Also  plume visualization
should be used more frequently than just during  full scale experi-
ments.  Many specific  phenomena may be qualitatively investigated  (and
photographed)  by smoke flows around the obstacle, and by small scale
releases within  the slope boundary layer flows.

3.4   Budget Estimate

     In order  to estimate the general  feasibility of the cost  of the
field experimental design, the following approximate values are pro-
vided.  A. study  about a 400 to 600 m high hill is postulated.  Two 40
day intensive  field study periods are  assumed, with 50 days of field
sampling and measurement operations.   Continuous meteorological data
collection and archiving for an 18 month period  are assumed.  The
costs of centralized  data logging equipment are  omitted from this
estimate and should be included elsewhere.

     3.4.1   Equipment  and Other Direct Costs 	  $ 2,147.600.

     3.4.2   Labor  135 man months @ $30/hr  (22  days
             per  montli)	     712,800.

           TOTAL (Labor, Equipment, and Other
                   Direct Costs) 	  $ 2,860,400.


                     PANEL LEADER:  Roy Evans


     John Eckert                      Gilbert J. Ferber
     Freeman Hall                     Norm Huey
     Rudolf Pueschel                  Ted Smith
     Ivar Tombach


     Measurement techniques appropriate for three scales of experi-
mental design were discussed by the Measurement Techniques Panel.
The smallest scale considered was appropriate to controlled tracer
releases over a small hill, with plume travel distances of km, as
described in the scenario submitted by  Bill Snyder.  The next larger
scale discussed was appropriate to the  concept of controlled release
over a 500-meter hill, with plume travel  distances of about 10
kilometers, as described in a scenario proposed by the Experimental
Design Panel.  The largest  scale proposed was appropriate to  impinge-
ment of plumes on elevated terrain (hills)  near an active power

     The chief differences among these three scales are related to
measurement resolution and plume sizes.  The small "100-Meter Hill
Experiment" would  involve relatively thin  plumes with  initial
vertical sigmas between 5 meters and 15 meters.  The  "500-Meter
Hill Experiment" would involve  plumes with vertical  sigmas of
40 to 60 meters prior to impact on the hill.  The full-scale  ex-
periment would also involve plumes with initial vertical sigmas
on the order of 40-60 meters; however, these would evolve over longer
travel distances (10 kilometers or more) to widths of more than 2

     Investigation on the impingement of a plume on a hill under
stable conditions,  regardless of the scale of the experiment,  was
considered to have four phases:

     (1)  PLUME RELEASE  AND GENERATION  (i.e.,  determining  the
          plume's  source  terms and initial conditions);

     (2)  PLUME EVALUATION  (i.e., the growth and changes  which
          affect plume  dimensions during plume transport);

     (3)  PLUME IMPINGEMENT  (the  actual process  of transport  of
          pollutant material through the  boundary layer);  and

     (4)  FLOW FIELD DETERMINATION (measurement  of wind  speeds,
          wind directions,  turbulence, thermal structure and sta-
          bility,  of the wind field which  actually  transports
          the plume.

     Each of the three scales of experimental  design involves
measurements of these different aspects of plume  generation,  trans-
port and evolution,  and impingement on elevated terrain.  How-
ever, each scale involves  plume  dimensions and resolution  re-
quirements which determine  the choice of measurement techniques.
Table 1 is a summary of techniques and their probable applica-
bilities to the experimental  scales.

     Discussion of  these  techniques is organized  generally  in terms
of experimental scale,  beginning  with the small-scale  experiment
and going on to the full-scale (or Real-World)  experiment.   An
experimental technique  is discussed under the first experimental
scale where it becomes  useful.


     This scale of  effort,  as discussed by the Measurement  Tech-
niques Panel, is similar  to  the concepts described in  the Snyder
Senario for the 100-meter  hill  experiment.  Broadly speaking,
modern technologies (lidar - instrumented  aircraft, remote  wind-
finding systems) are not  appropriate to experiments at this  scale,
and researchers must rely primarily on conventional techniques:
instrumented towers for winds and temperatures, integrated samples
(by syringe or bag)  for a gaseous tracer  (probably SFg), and plume
visualization by smoke  release.

     The panel did  make some  specific suggestions for the conduct
of the 100-meter hill experiment, which  can be summarized as  follows:

     (1)  Little cost would  be added to the experiment by release of
two different tracer species (e.g., SFg  and Freon-13) from  two

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different points, and dual release would enhance chances of observ-
ing a plume within the sampling network  and would very likely improve
knowledge of the wind flow field.

     (2)  The problem of sampling the plume prior to impact on the
instrumented hill is, at best, difficult.  Concentration measurements
can be achieved only by instruments on towers, which are expensive
to install and operate, and which cannot be established with suf-
ficient density to describe the plume prior to impingement.  The
use of a ground-based lidar for this purpose  is not recommended
by the panel for two reasons:  (a) the normal minimum resolution
"cells" for existing instruments are on the order of 3 meters, and
reducing this to 1.5 meters  to  resolve the  small plume as was
suggested in onj of the plenary sessions is pushing the instruments
into operational areas where their performance has not been verified.
Even if the instruments can, in fact, achieve practical resolutions
of this order, a relatively small number of cells would be obtained
within a plume cross-section, and the feasibility of performing
accurate contour mapping of  the  plume cross-section  cannot be
assumed a priori.  The feasibility of any such application  should
be verified before including  it  in the small-scale experiment.
(b) The ground-based instruments are expensive to operate ($40,000
to $50,000 per month in the field), and other methods would be more
cost effective.  A more effective method suggested by the panel is
the "Laser Illuminator" concept,  discussed below.

2.1  Gaseous Tracers

     The proposed experiments to study plume impingement on hills
or ridges require the use of a non-reactive, non-depositing tracer
that can be released at precisely controlled  rates and  measured
accurately at low concentrations.  For the distance scales being
consiiered (i.e., a few hundred meters for  a  "small hill" study
to a few tens of kilometers for a full-scale study at an existing
plant site),  sulfur  hexafluoride  (SFg) appears to be  the most
suitable tracer.  It has been used extensively as a meteorological
tracer and reliable methods of release, sampling, and analysis are
available.  Background concentrations in the  atmosphere  average
about 0.5 parts per  trillion  (ppt)  and commercially  available
electron-capture gas chromatographs can measure SFfi concentrations
accurately down to 1 or 2 ppt.  This sensitivity is quite adequate
for tracer measurements out to about 100 km from the release point.
This tracer is readily available  at  a cost  of about $3  per Ib.

     Other gaseous tracers currently under development, for example,
perfluorocarbons and heavy methanes, with  far greater  measure-
ment sensitivity (.01 ppt or  less), are intended primarily for
use to distances well  beyond  100  km.  If  multiple tracers are
desired, fluorocarbon 12B2 (CF2Br2), 114B2  (C2F4Br2),  fluorocarbon
13B1 (CFoBr) are  available  at somewhat higher costs  than SFg.

     A potential problem in the use of SF_  in meteorological ex-
periments is the variability of the background concentrations.  It
is used in large quantities as an insulating gas in high-voltage
power transformers and switches, hence, there are a large number of
sources that may produce localized  concentrations well  above the
average background level.   A survey of local SFg concentrations should
be included in the site selection process.

     2.1.1  Tracer Release.  SFfi is supplied as a liquified gas in
pressurized cyclinders and can be released  by a gas directly from
these cylinders.

     Required release amounts  would be on  the order of 1 Ib/hr
for the proposed "small hill" experiment; about 10 Ibs/hr  for the
"large hill" experiment (distance scale of  about 10 km)  and about
100 Ibs/hr for the plant site study  (scale  of about 50  km).  In-
dividual release durations of 3-6 hours should be sufficient to
accomplish the objectives of this study.  Elevated releases can
be managed with no great difficulty.

     Since one objective is to study the effect of release height
in relation to hill height and stabililty  profile, it  would be
more efficient to use two or even three different tracers (i.e.,
SFg, 12B2, and 114B2) released simultaneously at different altitudes,
at least for some tracer trials.  Releasing tracers from different
locations might also maximize  the information gained from each trial.

     2.1.2  Tracer Measurements in Plume Evolution.  It is desirable
to measure tracer plume concentrations and  horizontal and vertical
dimensions during its travel from the release point to the terrain
feature of particular interest.

     Real-time continuous SFg monitors are  available which can be
flown in a small aircraft to provide profiles of SFg concentrations
during a plume traverse.

     One version of this instrument, developed at Brookhaven National
Laboratory (BNL), uses the frontal chromatography technique to
provide continuous (but time-delayed) in-flight data for  a period


of 90 seconds or more.  It must then be backflushed  for about  2
minutes in preparation for the next 90-sec plume  traverse.  This
instrument has been successfully flown on many occasions.

     Under contract to the NOAA Air Resources Laboratory, Lovelock
has developed a truly continuous real-time instrument by eliminating
the need for a chromatograph column.  This instrument can  be used
either with SFg or perfluorocarbons and is  still under  develop-
ment by Lovelock as well as by Dietz at BNL.  Lovelock expects  to
deliver a flight-worthy prototype by January 1980.  Its sensitivity
should extend well below the parts per trillion level, with a response
time on the order of 1 second.

     Unfortunately, none of these instruments will have sufficient
resolution to obtain a true profile of the very narrow  plume ex-
pected in the "small hill" experiment.  They will, however, be able
to detect the plume and provide crosswind  integrated concentra-
tions through the plume.  The real-time instruments will be able
to provide a great deal of data on tracer concentration profiles  as
a function of altitude and distance from the source for the larger
scale experiments.

     2.1.3  Plume Impingement.  All three scenarios being considered
will require an extensive array of about 100 samplers to measure
tracer concentrations in the vicinity of plume impingement  on the
major terrain feature.

     Several methods are available for collecting whole-air samples
for SFg analysis.  The NOAA Air Resources Laboratories Field Research
Office (ARLFRO) at Idaho Falls  has developed  a  battery-powered
sampler that pumps air into a plastic bag, providing a time-integrated
sample at $100-200 per unit.   The units must be  switched on and
off manually.  Several hundreds  of these  samplers  are on hand
at ARLFRO.  Automated sequential whole-air  samplers, using bags
or syringes, are commercially  available at  a  cost on  the order
of $2,000.  An automated sequential sampler,  developed at BNL,
collects up to three samples in evacuated  steel  cylinders.  The
system is radio-controlled for simultaneous operation of all samplers.
Twenty samplers are available at present.

     Considering the large number of samplers required  (100) and the
relatively short sampling intervals desired  (10 min to  1/2 hr),  a
commercial automated sampler, providing 24 syringe samples, would
appear to be the best choice.  The other types of samplers  can  be
used to augment this network.

     For the "small  hill" experiment in particular,  the sheer
number of samples required may  be overwhelming (100  samplers x
6 samples/hr x 4 hours = 2400 samples per trial).  Meteorological
data or smoke plume information will have to be used for screening,
to select perhaps 10% of the samples for immediate  analysis in pre-
paration for the next trial.

     An alternative, to provide quicker turnaround, would be to use
analyzers that provide real-time readout (at 2-5 minute intervals
of concentration) to be fed into a centralized computer.  The cost
of such analyzers (about $6,000 each) plus the computer hardware
nould have to be weighed against  the cost  of  manual  processing
(perhaps $1/sample) and the need for rapid data processing.

2.2  In Situ Measurements of Wind, Temperature, and Humidity  from
     Towers and Balloons

     The measurement of meteorological variables — wind, tempera-
ture, humidity, pressure — by in situ  instruments in shelters or on
towers provides the data core for most  field experiments.  This will
oe true for the proposed complex-terrain plume tests also.  A brief
review of the expected accuracies and applicability  of such measure-
ments is, therefore, in order.

     For measurements of mean wind quantities, propeller or  cup
anemometers with vanes as required, are  quite suitable if  the instru-
ments are properly exposed away from flow obstructions.

     Standard cup and vane systems have a general  accuracy  of  +5
in direction and about +0.2 m/s for wind speed.  Resolution of the
wind direction is obtained to one degree.  Wind speed  threshold is
in the neighborhood of 0.25 m/s, but reasonable vane  response  to
wind gusts is limited to speeds above 1-2 m/s.

     Temperatures on the tower are generally recorded with a thermis-
tor or a platinum resistance thermometer in an aspirated radiation
shield.  Absolute accuracy of the thermistor is about  0.5°C with
resolution to 0.1 C; somewhat better accuracy and  resolution  are
available with the platinum resistor. Temperature differences on the
tower are recorded by voltage balancing between the two sensors.
Accuracy of Delta-T with thermistor is about 0.1°C.

     Relative humidity is best measured on the tower by  a dew-point
hygrometer system.   Accuracy  is  in the neighborhood of 0.5°C.

     For the accurate eddy-correlation  measurement  of turbulent
plumes, the distance constant for anemometers and the response time
for temperature sensors must be short enough  to  resolve all eddies
of significant size.  If we are to really understand the turbulent
impact of plumes onto rough terrain through the atmospheric surface
layer, then instruments with at least a ten hertz bandwidth must be
used.  This implies hot-wire or sonic anemometers and fine-wire
resistence thermometers.  Since  three-axis sonic  anemometers-
thermometers have demonstrated their accuracy  (to small fractions of
a degree and a meter per second) at the NOAA/NCAR Boulder Atmospheric
Observatory, they are a logical choice  for turbulent surface layer
measurements.  Data processing algorithms  compatible with mini-
computers are also available.

2.3. Meteorological Towers

     In situ instruments must be appropriately mounted, frequently
on towers, to place the instruments at  the desired heights.  Tower
costs increase quickly with  increasing height.  Estimates  for
costs of installed towers, with no instruments,  were obtained  by
asking for bids from a California-based contractor subsequent  to
the end of the Workshop.  These estimates assume that the towers
will be stressed for ice, wind, and lightning, and that they  have
de-icing heaters.  Each tower  is  equipped  with  four instrument
elevators, with a 19-wire cable to each elevator.  Cost  estimates were
as follows:

         HEIGHT                         COST

         50 meter                       $30k

         100 meter                      $41k

         150 meter                      $75k

     2.3.1  Remote Wind Sensing in the  100-Meter Hill Experiment.
The excellent range resolution and short-range measurement capabili-
ties of FM/CW radar provide important advantages for  monitoring the
the small-scale experiment.  Should there  be fine scale  wind shear, as
frequently occurs in stably-stratified valley atmospheres, this system
will be able to measure it.  Further, the intensity  of the  return
delineates these shear zones, thus providing  a record of descending
temperature inversions and the ubiquitous gravity and shear waves
associated with such interfaces.  Real-time wind readout will also
aid in properly placing the plume sources.

     With the range of the radar  of  several  kilometers,  changes in
the mesoscale or synoptic scale wind structure that might influence
the experiment can also be monitored.   Thus,  the arrival of  warm
fronts, or density currents  riding over and eroding the surface-based
nocturnal inversion, can be anticipated.

     Supplementing the radar  with CW Doppler lidar  or Doppler acoustic
sounders is also attractive.   These  lower cost,  more mobile  sensors
can significantly expand the  volume  of the atmosphere being measured
for winds.

     2.3.2  Wind Measurements with the FM/CW Doppler Radar.   The
FM/CW radar detects radiation backscattered  from index of refrac-
tion turbulence structure in  the  clear atmosphere.   A 10-cm wave-
length unit developed at the NOAA  Wave Propagation Laboratory  employs
phase measurement to detect the Doppler frequency shift  from the
moving turbulence that advects with  the wind. Good signal-to-noise
ratio is obtained  at ranges  up  to  several  kilometers, and the
minimum range can be as short as  20  or 30 meters.  Range resolution
as small as 1.5 m is feasible,  and  radial velocity  accuracy of  0.1 m/s
has been demonstrated.  Ground clutter restricts elevation angles
to 20° or greater.

     To measure both components of the wind, u  and v,  the radar
performs a conical scan about the zenith in a so-called VAD (velocity-
azimuth display) mode.  Asymmetry of the VAD velocity about  zero
provides a measure of the vertical  velocity, averaged  over the
diameter of the scanned circle.   A minicomputer  in the system pro-
vides real-time readout of winds versus height.  Separate transmitting
and receiving antennas are mounted on a trailer,  and a  separate
semi-trailer houses the radar electronics and data processor.  Setup
time for the equipment is approximately one  day on a level  site
20 m x 40 m; three-phase 208V or single-phase 240v, 10 kw is required.
A two-man per shift crew can  operate the radar once it is in place.

     2.3.3  Wind Measurements with CW Doppler Lidar.  A number  of CW
Doppler lidars have been developed  (at NOAA,  EPA,  DOT/TSC,  NASA,
Marshall) to measure winds by monitoring the  frequency shift  in 10.6
m radiation backscattered from atmospheric aerosols.  These CW  units
obtain range information by focusing the infrared radiation at the
desired range,  where the backscattered radiation then mixes efficient-
ly with the laser local oscillator on the photodetector.   These
systems are quite suitable  for VAD wind measurements in the clear
air at ranges to 500 m, although  range resolution is quite coarse
at ranges beyond 100 m because of the elongated  focus for typical
optical apertures of 20 to 30 cm. The units are  all mounted  in


self-contained  trucks.   Setup time on a level  site 10 m x 15 m is
four hours.   Single  phase 220V power, 5 kw, is required.   A two-man
crew per shift  is  required.

2.4  Laser  Illuminator

     •  Experimental  Use.  Plume visualization for the proposed
small hill  experiment can be accomplished using an aerosol  tracer
and several  laser  illuminators with suitable  recording devices.
The measurement technique is only applicable to a nighttime release.
Several laser illuminators are positioned between the source and the
hill, establishing thin planes of light perpendicular to the plume
path (see Figure 8).

     Plume  location  is  readily observable by the  experimenters and
plume dimensions can  be established through conventional photographs
or video taping with  one or more cameras positioned along the axis
connecting  the  source tower and the hill.

     •  Equipment Description.  All components, are readily  available.
Cost of the  laser  illuminator and camera for each plane is estimated
to be $10,000,  with  accuracy not limited by the experimental con-
figuration but by the  effort expended on edge detection in the images.
Illuminators  could be strobed to establish timing.   Another approach
using search  lights  may be possible.

2.5  Detection  of  Small Plumes by Electric Field  Measurement

     Electric field  measurements in connection with plume  trajectory
studies are  a novelty and need further exploration.  However,  if the
artificial  smoke particles are charged electrically, so as  to perturb
the atmospheric electric field measurably, field measurements  can be
a powerful  tool to detect a plume or even measure the concentration
of particles  in a  plume.  This could be done remotely from the  ground
by measuring  the field  as function of distance  from the  centerline
underneath  the  plume  with a field mill mounted on a movable platform
like a car.   This  could also be done airborne  by  a mill  mounted in
the nose of  a model  airplane that is remotely  directed across and
through the plume.  The  model aircraft speed is slow enough  to achieve
spatial resolution of 10   meters.  The technique, therefore, would
be applicable to scales that are expected in the 100- and  500-m hill

                                                    Light Planes
                   of Plume Cross Section
Figure  8.   Experimental  arrangement using laser  illuminators,


     In this experimental scale,  initial  vertical sigraas are on the
order of 40 to 60 meters, with travel  distances  of  the order  of
10 kilometers, and plume elevations  of 250  to 750 meters.  At these
scales, the conventional tower-based wind measurements must be aug-
mented or supplemented by tethersondes, minisondes and remote devices.
The doppler acoustic sounder is particularly well-suited to operations
on this scale, as is the FM/CW radar.   Tetroons  may  be useful  for
defining trajectories.

     Plume dimensions are large enough to satisfactorily use ground-
based lidar unibs for dispersion  parameter  measurements;  airborne
lidar can contribute to mapping the  impingement of the plume on the
hill, provided the plume is  tagged with a conservative particulate
tracer and is large enough.  In situ sampling with  instrumented
aircraft may or may not be useful, depending on the plume dimensions
selected for the release.  To effectively use aircraft, plume dimen-
sions must be of  the  order  of  several hundred  meters to a  few
kilometers; plumes less than a hundred meters are too narrow  to
effectively measure with aircraft.  Turbulence and wind fields aloft,
however, can be effectively  measured with instrumented aircraft.

3.1  Flow Field Determination by  Doppler Acoustic Sounding

     Transmission of an acoustic  pulse upward, and measurement of
the doppler shift of the echo which  is returned  from small scale
atmospheric turbulence, are  the basis  for one technique for  the
remote measurement of winds  aloft.   Such instruments, which are now
commercially available  (at a typical cost of $40 to $50,000) can be
used in a complex terrain study to define the wind and turbulence
field-, aloft, to determine the depth of the mixed  layer, and  to
illuminate localized phenomena  such as shear layers, inversion
layers, and thermal plume activity.  Recently-developed instruments
can be mobile and have a useful range  around one kilometer, which
makes them effective for intensive  or routine  field studies  of
plume dispersion aloft.

     Two different configurations of the Doppler acoustic sounder
are available.  Bistatic configurations,  based on designs  developed
at the NOAA Wave Propagation Laboratory (WPL),   are  manufactured
by the Radian Corporation.   A bistatic unit with a somewhat  different
configuration has been manufactured  by Xonics, Inc.   The  NOAA  WPL
also has several bistatic units of its own design.   (Such instruments
have a maximum range of 600 to 800 meters and a minimum range of from
100 to 200 meters above the  ground).   Monostatic configurations,


based on a design developed at the University of  Melbourne (Australia)
are manufactured by AeroVironment,  Inc.   These instruments have a
demonstrated maximum range,  under  appropriate  meteorological condi-
tions, in excess of one kilometer,  and a minimum range of under 30
meters.  All of  these  instruments  have different signal processing
techniques for extraction  of the wind speed; some of the performance
specification differences cited here depend both on the configuration
and the processing scheme.

     Either type of instrument has a  wind speed resolution of about
0.2 m/s and a maximum wind speed measurement capability of 25-35 m/s.
Vertical resolution of wind  speed  data is typically 30 m, although
resolution down  to 10 m is attainable.

     These resolution  scales make  acoustic sounders best suited for
studies around larger  terrain features,  although they can  provide
useful data on the higher level winds over smaller (100 meter) hills.
The absolute accuracy of  these instruments  is not well known.
Tests of acoustic sounders next to the NOAA  WPL 300 m  tower in
August 1979 should provide  some  information on this question.

     The choice  of bistatic  versus monostatic  configuration depends
on a number of factors.  Bistatic  units require a substantial area
(several hundred meters on a side) for laying out three or four
antennas; the monostatic antennas  are all  located at one point,
and mobile units are available.

     The bistatic system measures the wind in a single vertical column
of the atmosphere; monostatic units make measurements in several
directions from  the antennas,  and  then require  an assumption of wind
field homogeneity to construct all wind components.  In either case,
the wind measurement reflects an  average value over a substantial
volume of air.

     The lower height  limit  of bistatic systems is substantial, and
depends on the lowest altitude at which  the transmitting and receiving
antenna beams cross; monostatic system measurements,  on  the  other
hand, can begin  very close to the  surface.

     The maximum range of  bistatic systems is  also defined by the
antenna geometry, while signal-to-noise considerations define the
upper limit of monostatic  configurations.

     Because of the siting considerations, monostatic doppler acoustic
sounders are probably  best suited  for the proposed complex terrain

study.  Their versatility probably  outweighs the disadvantages of  this

     The routine recording  of  turbulence aloft by doppler acoustic
sounding should be  possible by 1980.  With the support of the Electric
Power Research  Institute, AeroVironment is  currently evaluating
various algorithms for  the  derivation of diffusing turbulence levels
from doppler acoustic signals.  This  evaluation  includes testing of
these algorithms against  in situ  turbulence measurements made on an
instrumented tower.  The resolution of such data should also be on the
order of 0.2 m/s (or better)  for  the  root-mean-square wind speed
variation.  This resolution will  be adequate for defining diffusion
under all but the  most  stable  conditions.

     Derivation of the  mixing  height  from the turbulence field is
straightforward.   In addition,  display of the amplitude of the return
signal in the traditional time-height form of a non-Doppler acoustic
sounder record, can illuminate the  atmospheric structures (shears,
thermal plume, inversions, local fronts) influencing the transport and
dispersion of the  plume.

3.2  Flow Field Determination  by  Tethersonde

     For measurements of  the structure  of the planetary  boundary
layer, a sensor package  carried aloft under a tethered kytoon was
developed several  years  ago at the  National Center for Atmospheric
Research.  This  instrument is now commercially  available from
Ambient Analysis,  Inc.,  in  Boulder, Colorado, under the trademark of
Tethersonde, for $8,000.00  to  $10,000.00,  depending on the options

     The Tethersonde instrument package consists  of sensors  for
wind speed, temperature,  pressure,  wet  bulb temperature,  and  the
orientation of the  package relative to magnetic north (which serves as
an indicator of wind direction since the instrument package orienta-
tion follows that  of the  kytoon as  it points into the wind).   An
optional thermal structure  function,  CT  sensor  is also available.
A rechargeable battery  provides enough  power for about four hours
of continuous operation.
     The package is carried aloft by  a  small, 3.25 m  kytoon.   With
relatively light winds  aloft (less  than 10 m/s)  the Tethersonde can
reach an altitude  of 1  km above the surface at a cool,  sea level
site.  To provide  additional  lift for use in stronger winds or at
higher altitude launch  sites,  a 4.25  m   kytoon is also available.
A motorized winch  handles the  tether  line.


     A radio-telemetry system  cycles through all data  channels
once each 30 seconds and transmits the signals to a ground based
receiver.  The data is printed on paper tape, along with the time  of
each scan.  An optional programmable calculator can be attached to the
system to calculate the balloon altitude by integrating the barostatic
equation, using data obtained during the ascent, and can also record
all data on a tape cassette for subsequent computerized analysis.

     The Tethersonde is a versatile sounding tool for  exploring
the structrue of the planetary  boundary layer in all  scales  of
complex terrain.  It is particularly useful  for study of  the  flow
over and around a hill.  Since it can be tethered at a relatively
constant height, it can be "parked" at the altitude of a plume and
will then provide a continuous record of the direction and speed  of
the plume-transporting wind.

     The system is portable, and can easily be operated by one
person with some practice, as long as surface winds are not strong.
The ground station requires 110V, 60 HZ electricity, which  can  be
provided by an inverter and a car battery.  launching and retrieval
in strong surface winds (above 10 m/s) is difficult, as is operation
when winds aloft exceed about 20 m/s.

     The response ranges and precision for the various components
recorded by the tethersonde are:

     Wind Speed          0.5 - 20 m/s          +0.25 m/s

     Wind Direction        0 - 360°            +5°

     Temperature         -50 - +50°C           +p.5°C

     Pressure  (Dif-        0 - 100 mb          +1 mb
     ference Relative
     to Surface)

3.3  Minisonde

     Simple, expendable instrument packages,  similar in concept  to
the Tethersonde package, can be  carried aloft  by  pilot balloons  to
provide soundings of temperature to heights  greater  than those
attainable by  the Tethersonde.   Tracking of  the minisonde balloon
by theodolite  allows calculation of the wind speed and  direction
profiles, provided that the ascent rate of the balloon  is known.
In flat terrain and a slightly stable atmosphere, the ascent  rate
can be assumed to be constant.   In complex terrain, or in unstable


or strongly stable atmospheres, a pressure  sensor  on  some makes of
sondes provides a direct record of the balloon  height or a  second
theodolite is needed to determine the balloon height.   Some sondes
also record wet bulb temperature.

     The rainisondes are similar in concept to radiosondes,  but
are easier to handle and much cheaper.  Although automatic radio
tracking of the sondes is not possible, the ground  stations  for
minisondes often provide for digital data recording  on cassettes,
and can contain all of the features of the  automated  Tethersonde
ground station.  Minisonde sensor performance specifications  are
generally almost comparable to those of the Tethersonde:  The wind
data derived from theodolite tracking is less precise,  however, and
its quality depends continually on operator skill.

     Minisondes are useful  for all scales of  complex terrain studies.
Because of the discrete nature of the soundings, and  their cost,
the sondes are best used to study slowly varying phenomena,  such
as flows well above the surface.

3-4  FM/CW Wind Finding

     All that has been said about the FM/CW radar for wind measure-
ments in the smaller scale experiment applies here as well.   The
range of the radar to several kilometers  is even more important here,
where towers cannot reach into the plume heights.

3.5  Flow Field Determination by Aircraft

     Within the framework of the "medium hill" experiment, the light
aircraft can extend the meteorological observation of  the plume en-
vironment.  This can be best accomplished  through horizontal traverses
perpendicular to the plume trajectory.  Sampling flights through the
plume can be used for this purpose, although it may  be desirable
to extend the horizontal traverses somewhat.  Principal objective
of the measurements would be to determine the homogeneity of the wind
and turbulence environment at plume level.

     Parameters of concern are:

     1.  Three-dimensional velocity components  (u,v,w) sampled at
100 HZ so that turbulent components as well  as average  values can be
determined.  Turbulence parameters are measured  by  a gust  boom
referenced to gyro-accelerator system which provides  a measurement
platform stable to low frequency fluctuations.

     Turbulence data  can be processed into OQ and a.  values for a
range of averaging  time.  Thirty second averaging  (about 1 km  of
flight path) is probably the longest time acceptable for  horizontal
mapping.  Accuracy  is reported to be + 0.1 m/s (Gilmer, McGavin and
Reinking, 1978).  Through these measurements, a horizontal  map  of
wind and turbulence can be obtained at plume  level  to be used  in
modeling inputs.

     2.  Flux parameters can also be measured if desired  during the
horizontal  traverses.  Both vertical height and moisture  fluxes can
be obtained by cross  correlation of temperature and humidity fluctua-
tions with  vertical velocity variations.  These data form an indepen-
dent measure of the diffusion environment.

3.6  Tracer Measurements Via In Situ Instrumented Aircraft

     The space resolution of aircraft measurements depends  critically
on aircraft speed and response-times of the instruments.   Light-twin
aircraft can be flown at speeds of 50 m sec   .  Time constants  of
instruments and gas measurements must be of the order of one  second.
Hence, the  space resolution of the sensing equipment is of the order
of 50 m.  This is probably good enough for tracer experiments of the
scales in question  for this experiment.

     Instrumented aircraft can be used to measure in situ the  concen-
tration perpendicular to the axis of the plume of tracer gases
and particles  (total  concentration, flight scatter  coefficient).

     It is proposed to measure centerline concentration and horizontal
dispersion of  particles  and gases.  Repeated measurements result in a
mean centerline  concentration and horizontal dispersion (ay ) of plume
effluents.   Repeating the measurements at  different heights from the
axis gives the vertical  dispersion  (pz ).

     Performing  the measurements at different distances from  the
source upwind  and downwind of the obstacle (hill) results  in  the
downwind dispersion at both sides of the hill, indicating the effect
of the hill  on plume  movement.  Aircraft tracer measurements,  includ-
ing data processing, will cost about $8,000/day, for most contractors.

3.7  Lidar

     •  Equipment Description - Several ground-based,  van-mounted
lidar systems  are available which are suitable for this type  of
experiment.  Systems  are available with calibrated scanning mounts,
a feature necessary for  obtaining detailed plume  cross-sections.


Spatial resolution of current systems  approaches several meters,
adequate for all experimental  scenarios  considered.   All  lidar
systems have real-time display  capabilities  and thus can be  used
to locate plumes  or  to direct  other  experimental  efforts  into
plumes.  Data output is in the  form  of hard copy  line profiles,
density plots, density contour  plots,  and processed and unprocessed
magnetic tapes.

3.8  Ground Based Lidar

     •  Experimental Use - The  ground-based lidar would find utility
in both the middle-sized hill  experiment,  and  in  a full-scale
experiment involving an actual  power plant source.  Much field work
of this nature has been routinely  performed  for a number of years,
and the methodology and equipment  are  well proven.   The spatial
resolution of existing devices  is  comparable to the  dimensions of
the small-scale experiment, but other  methods  of determining plume
location or dimensions may be more cost effective at this  scale
(see LASER Illuminator).  The  ground-based lidar  can be  used primarily
to determine plume dimensions  and,  in particular, the behavior of the
plume as a function of time.   A  workable method  of determining source
content is plume sampling by aircraft,  with subsequent extrapolation
and averaging of plume concentrations  using  lidar information taken
over extended time periods.  The lidar can also be used to determine
plume impact points with proper safeguards for  eye safety of experi-
mental help.

     Some features of specific  systems might  have additional benefit
to the experiment depending on  the actual site  chosen.  For example,
one available system (NOAA) has  the capability of measuring depolari-
zation ratios and thus discriminates between spherical particles
(i.e., combustion particles, oil droplets, etc.)  and background
fugitive dust.  Another system  (SRI) can be  used in  a mobile mode
pointing vertically upward.   If extensive road networks exist and
the scale of the experiment is  large,  this might prove of benefit
over scanning systems.  The lidar systems could also be used to obtain
meteorological information when not  being used  to for plume measure-

     •  Costs - Ground-based  lidar  systems can be operated for around
$50K/nionth excluding travel cost.

3.9  Airborne Lidar

     The airborne lidar maps  aerosol distribution beneath the air-
craft.  In particular, the airborne  lidar can be used to find the


dimensions and location of plumes.   In  the context of the  three
scenarios considered,  the airborne  lidar would only have  utility
in the medium hill controlled  release and the  monitoring of the
effluent from an actual power  plant.  The airborne lidar  and the
ground-based lidar can be used to determine  plume location,  cross-
sections between the  source and the plume, and  in addition, the
airborne system can be used to position a sampling aircraft  within
the plume for source  term determination.   Flights over the subject
hill in either the controlled  release middle size hill, or full-scale
hill experiments, would yield  plume impact information.  Figure 9
shows airborne lidar  returns  several kilometers  downwind from a power
plant source.  The second trace from the left  side of the photo shows
little scattering at  ground level,  whereas,  the third trace shows
considerable scattering due to plume  impact.
                  -   2km-
       CLEAR AIR
                  <   1km-
         REGION    Ground
                         Om    60m   120m   180m   300m  360m
                                Distance Along Ground Path
Figure 9.  Downlooking airborne lidar  showing  plume  contact with
ground.  Note ground level scattering  on  center  trace.
3.10 System Description

     •  System Description - At the present  time  two operational
airborne lidar systems exist and are  operated  by  the EPA Research
laboratory in Las Vegas (EMSL-LV).  The  system of interest is the
latest device developed by that laboratory;  a  two-frequency Lidar

utilizing a Nd-YAG Laser with  a  doubling crystal.  The device has a
vertical resolution of  10 m  and  horizontal  resolution dependent on
aircraft ground speed and the  highest  frequency of operation  (10
Herz).  The system's weight  and  power  requirements are compatible
with small twin-engined aircraft.   In  this type  of  platform  the
horizontal resolution is approximately 6-10 meters.  The device has
real-time display capabilities on  board the aircraft, thus enabling
the operator to tell other personnel  the plume location and height
and to position other sampling aircraft into  the plume.  A ground-
based computer system is used  to display and  to provide hard-copy
output in short time turnaround  after  the aircraft lands.

     Another airborne lidar  system is currently under development by

     •  Systems Cost - A rough  estimate of total system costs includ-
ing aircraft and ground-based  data system is  $4,000.00 per day of


     All of the instrumentation  mentioned so  far can be used with
full-scale tracer studies and  studies  of the  active  power plant;
however, the scales of  measurement are now  large enough that remote
and aircraft measurements become  most economical for most parameters.
The panel recommended that some  fixed  meteorological tower measure-
ment sites be established and  operated to collect a  lengthy  wind
record in this case also.

     The measurement of S0~  or other  combustion emission is so ex-
pensive, both in terms  of hardware and monitoring operations costs,
that :.s should be considered as  a  tracer species only if sufficient
funding becomes available for  a  "second-phase" or "verification"
study where models developed in controlled-release experiments
would be verified on actual  power  plants.  However, an investigation
of existing S02 monitoring  data around S0r> sources in complex terrain
may be desirable, and this concept receives further attention below.
Measurements at an active power  plant  would necessitate continuous
measurement of relevant stack parameters:  302  and/or NO  stack-mouth
concentrations, flow rates,  and  exit  temperatures.  These data are
available through conventional techniques but are very expensive to
obtain.  They are essential  to any "real-world" study.

     Other techniques become useful in measurements  on  an active
plant; Van-based correlation spectrometers  can be used  to locate


plume trajectories and estimate horizontal  dispersion  parameters.
Tetroons should be released to examine valley-flow  fields.

     Ground-based and airborne LIDAR become extremely useful  in
mapping plume cross-sections and impingement  of  the plume with the

4.1  Meteorological Measurements by Aircraft

     A light aircraft can be used  in the  "real world" experiment to
supplement the fixed and balloon-borne observations,  the principal
objectives are the horizontal mapping of  the  diffusion and the ex-
tension of sounding data above the  1 km level,  as needed. The latter
information, coupled with data from ground-based systems, could
provide the needed wind-diffusivity profile for model calculations.

     4.1.1  Horizontal Mapping Data.  During  the horizontal traverses
made by the light aircraft to sample the  plume concentrations, wind
and turbulence data can be gathered to permit horizontal mapping of
the plume environment.  Such a map would  give average wind and dif-
fusivity inputs into the model and would  permit an evaluation of the
spatial homogeneity of the environment.

     Wind and turbulence measurements are made by the airpraf,t bv
means of a gust boom, coupled to a gyro  or  INS system. U , V , W
are recorded at a  high data  rate suitable  for processing  into
(U'2 , V'2 , W'2 ) after arbitrary averaging times.   Wind  measurements
are made with the same system.

     In the real-world experiment, marked differences in wind and
diffusivity environment are expected as  the result  of terrain in-
fluences.  The light aircraft offers the potential of exploring
these variations within the limits of safe  flying.  The mobility of
the aircraft also permits its use  to explore  up-wind turbulent in-
fluences which may be advected into the  experimental area.

     4.1.2  Sounding Data.  The doppler  acoustic radar is expected
to provide wind and turbulence profile data to a height of 1 to 1.5
km.  At many sites, wind and diffusivity  data will be required to a
higher elevation.  The aircraft can be used to extend the sounding
data above the doppler acoustic radar so  that a  diffusivity-wind
profile can be obtained within the plume  environment.
       t   i    t
     U , V  , W   measurements,  together with an  INS  or similar
system, can provide both wind and  turbulence  information  for con-
struction of this profile.  It is  suggested that this might best be


accomplished by a series of horizontal  aircraft traverses (of about
30 sec each) at elevation intervals  of  100 m above  the acoustic
radar.  These data could then be  processed into  profile form  and
fitted to the acoustic radar data  to form a complete vertical profile
of wind and diffusivity.

4.2  Tetroons

     Tetroons are balloons  balanced  to  fly at  a  constant-density
level.  Tracking is accomplished  by  a tracking radar which records
azimuth and elevation at uniform  time intervals.  Winds can readily
be obtained over one-minute time  periods at the  level of balloon

     The tetroon is useful  in indicating parcel trajectories and in
providing detailed wind measurements along the trajectory.  Wind
speed accuracies of the order of  a few  tenths of a meter per second
can be obtained.

     The tetroon, however,  suffers from a few disadvantages.  Under
strong heating conditions,  the  constant density  surface tends to
decrease in above-ground-heights  as  the surface  temperature rises.
The balloon trajectory, therefore, may  not correspond to a plume
trajectory.  In  addition, tetroon oscillations may occur as the result
of the attempts of the balloon  to find  its appropriate density  sur-
face.  These oscillations may lead to wind measurements and tra-
jectories which do not represent  constant elevations above ground.

4.3  In Situ Aircraft Measurement

     It is suggested to measure in situ the horizontal distribution
of gases and particulates perpendicular to the plume axis.  Typical
gases are S02 and NO  (both reactive) and, if desired, SFg (inert).
Typical aerosol parameters  are  total particle concentration  and
light-scattering coefficient.   Due to negative  electric charges,
which the effluent particles acquire during or before exiting  the
stacks, they strongly alter the atmospheric electric field.   This
effect can be sensibly and  accurately measured with electric field

     Aircraft speeds of 50  m sec   of a light-twin and instrument
response times of the order of seconds for direct sensing of particles
and gases result in space resolutions of  50 m.  The response times of
field mills of 60 Hz gives  a space resolution  of  0.83 m.

     Repeated measurements  of  horizontal distribution at given alti-
tudes result in mean  concentrations and in horizontal  dispersion
parameters (°y) of the  aerosols and gases.  Repeated measurements
at different altitudes  give the vertical dispersion (az).  Repeating
these measurements at  different distances from the source gives infor-
mation of the downwind  dispersion (
                   PANEL LEADER:  Ronald E.  Ruff
         Jesse  Coleman
         Robert C.  Koch
         Donald W.  Moon
         J.  B.  Tommerdahl
V. E. Derr
Thomas F. Lavery
Joan Novak


     Data management and quality assurance,  QA,  programs are essential
ingredients  in  the conduct of the field experiment.  Though normally
treated separately,  we recognize the necessity for their integration
in the manner illustrated in Figure 10.   The  illustration shows  the
major phases of  data management and how information is fed-back as a
quality control  measure.

     The first feedback occurs after the routine data review conducted
in the field.   This review is the focal point  of data management  and
qualify control  in the field conducted  in a  near real-time environ-
ment.  The first review consists  of analyzing the data  for  (1)
relevance to the field objectives,  (2) planning  of future experi-
mental activities, and  (3) improper equipment  operation.  This latter
point serves as  a baais for the primary QA feedback wherein mal-
functions are detected on the spot.  Immediate  repair action can then
be undertaken by the appropriate field  personnel.

     The second  QA feedback occurs during the  final checking process.
This is normally accomplished off-site at  the  end of the activities.
Its purpose is primarily meant to eliminate  bad  data or flag question-
able data and replace these data with  correct values, if possible.
Lastly, an independent data review is normally  conducted by some user
other than the  field studies contractor.



     In describing the  various activities associated with data manage-
ment, we have distinguished field activities from off-site activities.
However, we  strongly  recommend that both activities be conducted by
the same group through the final data  archiving process.  One excep-
tion is our  recommendation for independent quality assurance audits
conducted by a separate group.


2.1  Introduction

     Requirements for  supporting field operations  are reviewed for
two extremes.  On one  extreme, only a  minimal number of data are re-
quired during real-time and other data processing  is  restricted to
rudimentary  displays of data.  On the other extreme,  real-time acqui-
sition, reduction,  and display of many parameters are  performed; in
addition, other  tasks  are supported such as initial reduction and
display of remote sensing data, back-up copying of all data, incor-
poration of  manually  entered  data, and selective editing.   In
accordance with  Workshop recommendations, we have  assumed a  two-
phase experiment will  be conducted.  Phase I would be the small hill
experiment;  Phase II would be a full scale experiment at a power
plant site.

     The determination of the data processing scheme  depends  upon
(1) the specific  requirements of the experiment,  and  (2) similarities
between the  Phase I and Phase II experiments.   If  the Phases  are
similar, the selected  field data system and procedures  should be the
same for both phases  so that Phase I serves as  a shake down of the
system for Phase II.

     Quality assurance procedures remain essentially the same regard-
less of the  complexity of the experiment.  However, data  review is
more easily  accomplished with  the aid of adequate data display
facilities on site.   Also,  the ability to enter manual  calibrations,
corrections, or  logistical information while still  in the field is
desired.  A  small computer system may not support such field entries.
Hence, these functions must be performed offsite with perhaps some
loss in data integrity.

     In the  following  sections, we describe general  requirements for
three field  functions.

     (1)  Data Acquisition,  Preliminary Reduction, and Archiving —
          specifying the forms of data acquisition, what field calcu-
          lations must  be  made,  and the data product that is gener-
          ated in the field.

     (2)  Data Review — specifying the on-site information required
          to  (a) check  the validity of the data in a timely fashion,
          and  (b) to support the  planning of future field (experi-
          mental) operations.

     (3)  Procedures and Calibration — describing the pre-field and
          field activities required to maximize the quality  and
          integrity of  the data.

     Lastly, we recognize  the special  requirements posed by remote
sensors.  Accordingly,  we  address  these in the last sub-section.

2.2  Data Acquisition,  Archiving,  and  Preliminary Reduction

     In discussing the  requirement for the field data  management
system, we have resticted ourselves  to generalizations to some extent.
The actual requirements are directly related to the complexities of
the field measurement plan.

     2.2.1  General.  The  following features are described for most
types of field experiments that  are foreseen:

         •  All data should be available in semi-finished form within
            12 to 24 hours for experimental planning and review.

         •  Those data  required  for decision making and the general
            management  of experiments in progress should be displayed
            in real time.   These data  should include  sufficient
            meteorological information to determine if conditions
            are favorable  for the  conduct  of other measurements
            (e.g., tracer  release). It is highly desirable, but not
            necessarily cost effective, to display real-time ground-
            level concentration  values.  Graphics display  of  real
            time is also highly  desirable but not necessary.

         •  All data should be archived in the field in  raw  form
            (without necessarily being converted to more usable
            parameters  such as diffusion coefficients, plume height,
            and so forth); this  stage  of data reduction and conver-
            sion will be reserved  for  a later time.

            All data  should  be  backed up by duplicate records;  data
            tapes should  be  duplicated in the field or off-site as
            soon as possible.

            Strip charts  should not be used for the primary  data
            record although  they are acceptable as backup.

            Handwritten records of  maintenance and  calibration teams
            should be carefully maintained for later use  in error
            flagging,  quality  estimation, and editing.

            The data  archival  system should include a quality index
            technique to  flag  poor quality data and data that  have
            been edited.

            Certain sensor and system status information  (e.g., power
            critical  voltages,  flows) should be routinely acquired
            and entered on  the  raw data tapes.

            The data  acquisition system should include  an automatic
            error flagging  system for "obviously" erroneous  data
            (i.e., extreme  values or rates of change).  This  will
            help to identify and correct malfunctioning  instruments.
     2.2.2  Different  Types of Data  and How  They Are  Archived.

            a.  Continuous Data.   Continuous data are considered to
be hard wired  (or otherwise transmitted) into a data logging computer
that records basic  signals representing wind speed, temperature,
continuous ground-level  concentrations,  and so forth.   These  data
should be stored on disk or magnetic  tape, automatically  checked for
errors, and made available for real time display.

           b.  Batch Data From Self-Contained Systems.  Batch  data
include those  data  from  remote sensors,  mobile or remote systems
(such as aircraft,  tethered balloons,  pibals,  etc.),  and batch
processing of  bag samples.   Some  of the data may be available  on a
nearby real time basis (such as remote sensing systems).  Others may
not be available  for hours.  These  data will be available in different
forms and it is not  necessary that  they be combined  onto a  common  tape
in the field.   Care  should be taken,  however, to insure that all tapes
can be easily  read  by  the central,  off-site computer at a  later date.
All data from  these various systems should be processed, on-site,
to the extent  required for program management.  For example, lidar
data should be processed for examination of trajectories and plume


cross-sections.  All systems  measuring the same thing (such as FM/CW
radar,  tower wind instruments,  and tetroons) should be  compared for

      2.2.3  Data Acquisition  and Archival System.   The configuration
of  a  data acquisition and archival system can be  outlined in only a
general way  until the field data requirements are  specified exactly.
As  a  minimum requirement, key meteorological parameters should be dis-
played  and stored on a  real-time basis.   (If such parameters are to
be  routinely monitored at times other than during the intensive field
periods,  it  may be cost effective for the field computer  to remain in
the field.  At the other extreme, a more comprehensive computer could
be  needed to process more real  time data,  display  auxiliary remote
sensing data, and extensively support  data archival. For this more
demanding requirement,  we estimate that a more comprehensive field
mini-computer facility  will be  required.   Peripherals could include
a disk, three magnetic  tape drives, interactive  graphics display
terminal  (perhaps two), and a high speed (electrostatic) printer/

2.3  Data Review (Field)

      Non-real time detailed review of data is expected to  be conducted
off-site  incorporating final checks of consistency, extreme value and
other automated data checking techniques.  Final calibration adjust-
ment  of data is also expected to be accomplished off-site.

      Real-time and near real-time preliminary on-site field review of
data  is limited to that necessary  to determine the  proper working
order of  instrumentation and  recording equipment,  and that necessary
to  operationally plan the successful  conduct of  the experimental

      Preliminary quality assurance of  instrument  recording,  conver-
sion, and transmission may be accomplished by spot check comparisons
of  manually  reduced analog information and recorded  digital informa-
tion.   Computer graphics may be  beneficial for reproducing the analog
trace for comparison with back-up chart recording.   Real-time compari-
sons  of wind and temperature  field data for consistency should also be
accomplished in the field.

      Real-time wind and temperature  field data available in the system
provides  an  exceptional operational planning  tool.  While it  is
important to assess the possible  overriding effect of  synoptic weather
situations on operation of the  experimental  program,  it is essential
also  to assess the diurnal effects of  topography  and temperature


gradients as reflected in the wind and temperature field data recorded
for the past 24-36  hours.   The trends established concerning the
timing of drainage  flow,  the intensity and  height of the nocturnal
surface static  layer,  break-up, and wind  direction and speed provide
good indication of  whether the day's activity  should be devoted to
intensive measurements or  perhaps maintenance  and calibration and
other activities.

     Some meteorological and other measurements essential to meaning-
ful description of  the wind and thermal  field, such as pilot balloon
observations, by nature require manual entry  into the system for near
real-time operational  planning.  These should  be reviewed and compared
with other wind data  for  consistency.

     Additionally, it  is assumed that sufficient climatological infor-
mation for the  immediate  area  of  concern  is made  available for
operational planning  purposes.  Such data should be entered into the
system for recall and display in a meaningful form by  the field
program director.

2.4  Procedures and Calibrations (Quality Assurance Program)

     This section covers the essentials of  the QA program as conducted
in the field.   Our  purpose is to delineate  some  general (and a few
specific) procedures which  are applicable  to the field preparation and
field activities phases of the program which  will be useful in assur-
ing data quality.   In this regard, it is recommended that a general
quality assurance program  be activated which will have as its basic
elements:  (1)  review of  instrumentation and system specifications;
(2) the review  of the calibration and operational procedures for the
various instrumentation and data acquisition  systems; and  (3) the
independent audit of  all  measurement and data systems, where appli-
cable.  The individual elements of such  a recommended program are
discussed in the following paragraphs.

     2.4.1  Review  of the  Instrumentation  and Data Acquisition System
Specification.   After  the program design is firm, including a prelimi-
nary selection  of instrumentation and data systems, it is recommended
that a review be conducted of the measurement and data system speci-
fications and operational  characteristics to determine how well they
meet the performance  requirements as dictated  by  the program plan.
This analysis should  include an evaluation of such specifications as
instrument accuracy,  resolution,  response  time,  range,  minimum
detectible limit, environmental constraints and data output configura-
tions as imposed by the program requirements.

     Implementation of such a review may  be  best accomplished by a
panel of several people who have collective experience and expertise
in the areas as dictated by the final program plan.  It should include
people knowledgeable in the individual instruments, data systems, and
the utilization of such systems in  the  field environment.

     2.4.2  Instrumentation Calibration Techniques Review.  Prelimi-
nary to the actual field  operations, a  review of the calibration
techniques should be conducted.  This should consist of a review of
the calibration techniques and procedures as proposed to be used by
the field unit  for each individual  type of  measurement  and data
system.  Information should include the frequency of calibration,
type of calibration, traceability to an NBS  standard, where appli-
cable, and a functional  diagram of sufficient detail  to allow
understanding of techniques employed and identification  of major
components; a calibration procedure document including an example
calibration formation record form,  should be included.

     Submission and review of these documents should be sufficiently
early in the program to allow for revision as required.

     2.4.3  Review of Operation of  Field Systems Procedures.   A
field program of the type under consideration may impose several
requirements on one or more of the  measurement  systems.  A proposed
field system operational  plan should be developed which would de-
lineate the expected deployment  of  instruments,  indicating the
expected range  of environmental conditions, operating modes, use time
or duty factor, primary power supply voltage and frequency range
expected and the calibration and maintenance schedule.

     A review should be made of the expected degree of degradation
that these combined factors may have on data  quality.  Experience in
operation of similar instruments under the expected operational condi-
tions is needed to make this assessment.

     The effect of electromagnetic  interference should also be in-
vestigated.  Such things  as high power  radio stations  and radar
installations can cause noise in the recorded data.  This noise may
be coupled into the system via electric field interference in high
impedence circuits and/or magnetic  field coupling through long data
or signal lines.

     Recognition of this  problem and logging of operational infor-
mation can be very useful  in identifying these artifacts in the data.

     2.4.4  Measurement System Audits.   In-field  audits of  all
measurement and  data systems are recommended.   Audits should be
conducted for  both  the sensor outputs and key  status  measurements
(e.g., flow rates for collection devices).  The frequency of  the
audits depends on the desired degree of independent assessment of
the data quality commensurate with the type  of instrument  being

     Audit procedures for most of the gaseous analyzers,  such as SO,,,
NO-NO , and 0,,,  have  been developed by EPA.   A considerable amount of
information is available to guide  the designer in the expected
accuracy and stability of some of the instruments.   Audits of meteor-
ological and remote  sensor measurements systems are also  necessary for
this program aud some reasonable effort  should be expended in review-
ing and improving audit procedures for these devices.   For some of
these sensors  "injected signal" techniques should be used where over-
all performance  cannot be  verified.

     An audit  of the data acquisition system should be carried out to
determine the  correctness  of the transfer of the output signal from
the respective measurement systems through data processing.  This may
be accomplished  by  monitoring the output of the respective sensors
for selected increments of time and then  comparing these  values, which
have been independently corrected for  calibration functions, etc., and
then comparing these data to the output at the central  data processor.
This allows also for the checking of the proper applicability of all
calibration equations and  correction factors.

     If any unit fails to  respond correctly to an audit, an appro-
priate notification must be made to the  Field Director.   Every effort
must be made to  ascertain  the cause of the failure  and to document
the circumstances, duration  of the failure (if known), and procedures
to correct the data,  if possible.

2.5  Special Considerations  for Remote Sensors

     The following  material  is keyed to the outline of the  panel
recommendations.  It  consists of recommendations for  the special
consideration  that  must be given to the  data from remote  sensors such
as radar, lidar, and  acoustic sounders.  In general,  each remote
sensor has its own  data acquisition system and will provide  a
computer tape  (probably 9-track,  phase encoded, 1600 bpi) on which
will appear files containing calibration  runs, background  information,
and data.

     In the case  of  ordinary lidar, this data will  be  backscatter
coefficients as a function of range,  perhaps with separate files for
separate wavelengths and separate polarizations.  One or  all of these
may be present depending  on the files.  The lidar data  must be pro-
cessed to remove  the effect of the inverse square of the range, all
drifts must be removed,  the zero point  identified,  and the calibration
factor applied.   Programs exist to perform these  functions.   They
can be applied by the lidar  crew outside  regular working  hours or the
programs may be adapted to use on the field director's computer.
Because of the differing  formats for tape storage,  it  is  probably
most useful to use the field director's computer.   Hard  copies of
graphs of a few shots can be produced quickly by the lidar crew for
evaluation of plume  spread.  After the above, processing data may be
displayed, averaged, or otherwise processed.

     A Doppler radar (e.g., FM/CW) produces information on back-
scatter coefficients versus range and the radial  velocity versus
range.  The data  is  displayed in the field and digitized and placed
on magnetic tape.  Data processing programs exist and can be adapted
to the field director's computer.  Increased  information  on  three
dimensional velocity fields can be obtained by  using dual-Doppler
radars.  In this  case,  the  outputs of  both radars must be combined in
a computer; probably the  field director's  computer must be  used
because the existing radar  computers don't  have  this capacity.

     Acoustic sounders also produce magnetic tapes containing infor-
mation, on repeated  scans, on the backscatter coefficient vs. range,
and the Doppler shift versus range.  Probably some development of
programs is required here because the field director's  requirements
for display must  be  considered.  The acoustic sounder data is often
usefully displayed in a facsimile form to obtain an immediate view of
the structure of  temperature inhomogeneities.  Extraction of acoustic
Doppler information  is available to present wind velocity vs. height.

     2.5.1  Objectives.  The objectives of data management for the
remote sensors are essentially the same as for  other data sources.
However, remote sensors are often called on for data to  guide the
field director in the choice of operating parameters at his disposal.
Some of the data  must be  available in real-time and most of the data
must be available for review within twelve hours in a form from which
good, but not necessarily  final, estimates of relevant parameters can
be made.

     2.5.2   Requirements.

            a.   Phase I  - The Small Hill Experiment.  Probably,  at the
most, one remote  sounder will be present,  and only a small computer
facility under  the field director (part of  the remote sensor system).
In this case the  remote sensor computer must produce hard copy  graphs
or photos or charts or tables of its  output for use by the  field
director as well  as a complete tape record of its data.  A sampling
of theses must  be available in essentially  real-time to the director.
More complete processing must await transmittal to a central  facility.

            b.   Phase II - Full Scale Experiment.  Probably one  or two
lidars, one or  two radars,  and one or more acoustic sounders will be
employed.   The  additional complexities of  this  experiment, and its
multiple objectives (depending on weather  conditions and where the
plume is going) require the same essentially real-time availability
of remote sensor  data to the director as  in Phase  I.

     2.5.3   Data  Review Support.  Each remote sensor data acquisition
system must possess the capability of automatic rejection of data
(non-recording) when the predictable mishaps occur, such as misfires,
intolerable power fluctuations or other debilitating failures.  This
minimizes bad data on tapes.  Each remote sensor system must periodi-
cally test  for  correct  operation in such a way that the result  shows
up on the data  tape and is  identified as  a calibration file.  The
results of  these  tests  must be  examined  by the computer during
processing.   The  remote sensor operator must also  supply standard
tests to apply  to data while processing.   Whenever possible,  known
physical measurements that  test entire systems  should be employed.
Error estimates must be supplied by the remote  sensor crew.

3.1  Introduction

     The general requirements off-site consist of provision for final
reduction, completion (i.e., merging, organization,  storage,  re-
trieval), final quality assurance checks, and  data products useful
to the model development and evaluation  community.   The complexity
of this activity is  direcctly proporational to the overall complexity
of the experiment  and what is accomplished  in situ,  while  it is
preferred that some  final  reduction (i.e. , conversion and validation)
and some compilation is performed in the  field,  it is recognized  that

some may be required at an off-site facility.  Clearly, a large off-
site facility (e.g., EPA's Univac 1110) is needed to store the final
archive and thereby serve as a clearing house  for future data

     The field team should have  the primary  responsibility for the
initial off-site activities because,  simply  stated,  they are most
familiar with the data and hence in the best position to validate
it.  Their participation  should  continue through the establishment
of the final archives.

3.2  Compilation

     The compilation phase of  data management involves accession of
all data collected during the  study period and all associated conver-
sion, reduction and error checking.   The first  consideration is the
type and form of the collected data which may  obviously be contingent
upon the availability of  an on-site computer during the experiment.
The following is a  list of the general data types — (1) continuously
monitored data which can be directly fed into  the on-site computer or
collected on data tapes;   (2)  manually reduced data such as  lab
analysis or pibal soundings;   (3) self-contained systems  such as
Lidar, Sodar or Radar;  (4) equipment  logs, calibration and audit in-
formation; and  (5) preliminary  analysis and error detection used
during the field planning review meetings especially if an on-site
computer was available.   If an on-site computer was not available
during the experiment, some additional conversion equipment (e.g.,
A-D) may be required for  data reduction.

     The basic functions during the compilation phase are as follows:

     1)  Collect all data tapes, logs,  etc., and associated documenta-
         describing format and content of the data tapes.   Enter
         all marually collected  data  onto the computer.

     2)  Make backup copies of all original  data tapes.  label and
         store these along with  copies of associated  logistical
         documentation.   An informative leader at the beginning of
         each tape  should be  included.

     3)  Perform preliminary  automatic error  checks.   Devise a
         system to  incorporate status,  calibration,  and  log book
         information.  Develop preliminary error flagging schemes.
         Correct obvious  errors.

     4)  Perform appropriate data conversions and  reductions  to
         produce raw data in standard file formats.   This  results
         in the first level of data archive.

     5)  Perform required  time  averaging  and preliminary data
         analysis to calculate intermediate parameters required  by
         the modelers.

     6)  Design and prepare second level archive which may include
         merging of certain data sets.

     7)  Acquire or develop a data management system for simple
         retrieval and display of the second  level  archive data.

     8)  Develop software to produce higher  level  archives and
         data products.

     In order to perform these functions it is necessary to receive
from the modelers a specification of the required temporal and spatial
resolution and a list of calculated parameters that are required  as
input to the model.  In addition to data collected  during inten-
sive periods, two other types  of  data must  be managed.   First,
climatological data may be collected for a prolonged  period.  Pro-
cedures must be developed to verify and archive this long term data
set.  Finally, an effort should be made to obtain all data available
from other studies which may shed some light on the complex terrain
problem.  A method of archiving and retrieving this  data should  be
developed to provide easy access for the modelers.   A special effort
should be made to obtain and integrate data from the  DOE and EPRI

     The data management and quality assurance panel recommends that
the contractor provide EPA with all original  data  and at least two
forms of the archieved data and associated software so that EPA may
act as a clearing house for distributing the  data  to  modelers and
other contractors.

3.3  Final Checks and Analysis^

     One of the principal components of the data management task  is
to assemble and guarantee a valid, reliable data set  to be used  by
the model developers.  Inherent in these tasks are  error checking
and analysis procedures  at  three fundamental levels  in the chain from
field measurement  to model development.   These  levels  include
1) Analysis in the field (see Section 2.3),  2) Analysis by the data
manager, and  3) Analysis by the  modeler after the  data set  is


final.  In this section  some automatic, computerized, and analyst-
invoked error-checking procedures contained in the data base manage-
ment system  (DBMS)  are described.  The  DBMS should include a modular
set of error checking procedures from simple range checks to sophis-
ticated numerical  techniques while maintaining a human decision
factor in any data  modification.  The system should contain a formal
process for updating the data base and reporting all  modifications.

     Separate procedures can be developed for  single and  multiple
sensor error checking.

     3.3.1   Single-Sensor Error Checking.  There are five  basic error
checks for individual sensors:

               Range Checks

               Rate of Change Checks

               Calibration Analysis

               Outlier Detections

               Time Series Forecasting Techniques

The first two can  be computerized to provide an automatic method for
flagging potential  errors in  single-sensor data.  Range  checks include
searching for both certain and possible  errors:  For example, include
negative air quality concentrations.   Possible errors can be deter-
mined by comparing  the measurements with  established climatological or
"reasonable" values. For example, solar radiation data should follow
a diurnal cycle and exhibit  a reasonable daytime maximum.  Similarly,
maximum daytime temperatures at a particular locale should not exceed
35 degrees C, for  example.   The temporal rate of change  of selected
variables can be compared to probable maximum rates, e.g., a tempera-
ture change  of 10  degrees/hour.  Similarly, most operational instru-
ments display certain small  random changes.    If these are  not
exhibited in the data,  it could indicate a stuck or  frozen instru-
ment, excluding those with natural constant states,  e.g., zero air
quality measurements.

     Analyst invoked (manual) error checks could include  an examina-
tion of the  calibration  history of an  instrument.  Rapid changes in
calibration  constants  are probably indicative of  malfunctioning
instruments.  Unfortuantely, it may be necessary to apply nonlinear
correction factors to  recover valid data.  Outlier detection pro-
cedures include polynomial  or  spline  curve  fitting to the  time


varying data points.  Most  real aerotnetric data  samples  should
reasonably approximate the predicted curve (Figure 11).  Outliers from
the predicted curve could indicate  incorrect samples which  could be
corrected by the "predicted" values.  (Such  corrected values must be
flagged accordingly in the  data  record).  Time  series forecasting
techniques include trace analyses  (useful for  determining  drifting
calibrations) and principal component analysis.  Table 2 summarizes
some of the available single sensor  error checks.


Range                                   ^ > Q

Rate of Change                          JZ < 20°C/hr


Calibration                             Spline Fits

Outlier Detection                       Polynomial Fits

Time Series                             Fourier Fits

                                        Baseline Offset

     3.3.2  Multiple Sensor Error Checks.   Again,  multiple sensor
error checks can include both automatic  and analytical procedures.
Some of the automatic checks include  a comparison  of  pairs of data
to established identical or probable  physical  relationships, e.g.,
N0x = NO + N02 ; T _> TQ.  Statistical relationships derived  from
climatological data can be used  to  isolate  low probability events
that can be flagged for further examination.  Manual checks  of
multiple sensor data can include graphs,  tables,  scatter  diagrams,
line plots, contour diagrams and perspective plots.   These simple
exhibits for visual pattern recognition will  enable the rapid evalua-
tion of the data.


           Data Point
Curve Fit
          Figure  11.  Example of outlier detection.

     3.3.3  Update Procedures.   The simple automatic analysis-invoked
error checks should be  designed to  detect possible errors.   Only
the analyst should be allowed  to actually change a suspect value.
Each change should be identified in  a report and in the  archive,
as follows:

               New Value

               Date/Time  of  Change

               Old Value

               Reason for the  Change

Values that are suspect and  not changed in the archive should be
flagged (according to a prescribed  code) for the  modelers' informa-
tion.  The updated report then becomes a permanent part of the data

3.4  Data Products

     There will be three basic  data products coming from each experi-
ment including an archive of raw data, a model  development  (and
analysis) data set and  a  summary report describing the data.  The
data archive will be a  corrected and edited compilation of all data
acquired in the field program.   It will be available in total and in
subsets without further processing  to meet requirements not met by
the model development data set.   The  model development data set will
include such parameters as are needed for model development, evalua-
tion and diagnosis, which are  specified prior to and in the course
of the program.  The parameters will be averaged over specified  times
and vill include values derived from combinations of archived values,
such as plume spatial distribution parameters a   and o   and various
stability parameters.   The summary  report will describe the experi-
ment, the types of data available,  the accuracy  of the  data (as
indicated by audits and parallel measurements),  and a quantitative
summary of the data available  in each intensive  period.

     Another data product will be processed data from other  field
studies.  It is desirable to prepare data from other field studies
at least for model evaluation  if not also  for model development

     3.4.1  Data Archive.  An archive of raw data should be maintained
so that it is available for  special  purposes not foreseen in the


present study.  Selected  subsets for designated time periods or ob-
servation systems should  be  available on request.  The  volume  of
data can be condensed  by  eliminating useless data,  e.g., lidar
scans which do not  intersect the plume and which are not required for
background data.   The archive will be  edited and corrected for instru-
ment calibration and audit results so as to contain the  best possible
measured values.  The  contents and organization of the archive should
be described  in the summary  report.

     3.4.2  Model Development Data Set.  A model development data set
should be derived from the archive to meet the specified requirements
of model developers and model evaluators.  This  data  set will  be
significantly reduced in volume from the data archive to  be  convenient
for data handling purposes.   The parameters will  be averaged  and
otherwise characterized over the period of  interest.  Specified
parameters will be  derived;  e.g., ground lidar observations could be
transformed into  cross-sections of hourly mean back scatter for fixed
distances from the  source.   Each cross-section could also  be charac-
terized by a center  of  mass position and    and    values.   Similarly,
wind observations can  be  transformed to mean  values and  specified
turbulence statistics.  Any  number of stability indices can be com-
puted and placed  on the file.  It's  desirable that modelers be given
parameters expected to be useful to  fit a priori model concepts and
to be useful  to diagnose  why the expected  concepts do  not work.

     A program must be developed to  create the model  development
set.  In view of  the complexity and  variety of  types  of  data anti-
cipated for use in  the planned programs, it is  recommended that on
the order of  6 person-months be allowed for  development of  this
program.  A modification  of  the program used  to  generate the model
development data  set could be used to process data from other field
studies in complex  terrain.   The primary modification  would concern
interfacing with  different data formats.

3.5  Summary  Report

     A summary report should be prepared to describe the  data in order
to help modelers  and others who deal  with the data to select portions
of the data and to  comprehend its scope.  The report should include
at least the  following











     The effort required to summarize data is  highly dependent on the
volume of data required.  However, the summary  is not expected to be
a major part of the data management and  quality  assurance effort.
Perhaps 5 percent of the overall data management effort should be
allocated to generating a summary.

4.   COSTS

     Costs are proportional to the complexity of the experiment,
requirements of the field crew, requirements  of the model developers
and evaluators, and the number of intensive  field periods.  For our
purposes, we have assumed an upper-bound of  likely requirements for
two field study periods.  It should be noted  that  once the  data
management software and QA procedures are established for one ex-
periment, costs are much less  for a  second similar experiment.

     In general, we anticipate that 12 to 13 person-years will be
required for the two phase approach  suggested  by  various panel
members.  Personnel and support costs (i.e.,  travel and subsistence,
report reproduction, miscellaneous supplies)  could consume about one
million dollars.  Taking into account the need  for a field  data
facility (about $130,000) the above costs are  consistent with general
estimates that data management and QA costs each  account for about 10%
of the total budget.  If Government Furnished Equipment is available
for the field  data  facility,  the above $130,000  data facility
estimate can be reduced accordingly.


     During the course of the Workshop the panel became quite con-
cerned that the experiments would not satisfy the primary objectives


to improve modeling in a complex  terrain setting.   Specifically, a
better understanding of plume impaction is desired as  a  first
priority.  Towards this goal,  field  studies are planned to collect
the necessary data which will enable us to refine existing or develop
new and improved model formulations.

     Other panels have presented  details and recommendations  on the
above topics.  They describe alternatives to achieving the stated
objectives.  However, our panel would like to address some of the
issues.  In particular, we would  like to express  the need  for a
consistent approach in the follwing  two areas:

     1.   The measurements should be consistent with the  need to
improve the model in  settings of  complex terrain.   Therefore,  we
need measurements to  verify  model performance (observed air quality
concentrations) and to verify our estimations  of  certain inter-
mediate derived parameters.   In particular, if we  are considering
Gaussian models, there is a  need  for measurements  of the vertical
and lateral spread of the plumes  as  a function  of downwind distance
(or time).  There is  also a  need  to measure the  flow characteristics
of the plume in the vicinity of the  terrain  obstacle as  well as
upwind and downwind.

     Flow visualization is one means of describing the above
parameters and is essential  in our opinion.  If we rely solely on
measurements of ground-level tracer  concentrations and conventional
meteorological parameters, we fall into the pattern of many previous
field experiments whereby we  obtain answers for a specific regulatory
problem but fail to sufficiently  enhance our understanding of the
basic processes that  are occurring.

     2.   The scale of the experiment shoud be consistent with our
ability to measure the required parameters.  We support the concept of
first conducting a simple experiment,  fixing certain parameters  (i.e.,
height of the plume,  source  strength, and characteristics of the
obstacle).  However,  having  gone  to  this trouble,  it seems only
appropriate that we adequately measure other non-fixed parameters to
the extent practical.  In this respect,  the scale of the experiment
should be consistent  with measurements needed to parameterize the
model input parameters (e.g,  meteorological tower  measurements),
verify model predictions (e.g. , ground-level tracer concentrations),
and verify parameterizations within  the model (e.g., visualization
of plume spreading and flow  patterns).

     3.   It is essential to  develop  a method of  routine meteorologi-
cal monitoring to characterize plume  dispersion in rough terrain.  In


principle, wind speed and  direction,  turbulence data (vertical and
lateral), and mixing height are sufficient (assuming adequate spatial
resolution).  Of course, there is  the problem of  relating turbulence
data to the plume dimensions.   The horizontal wind direction varia-
tion, aQ  , may be appropriate for  quantifying  the lateral plume
dimension, normally quantized  as a .   For quantifying the vertical
plume dimension, a   we may wish to consider measures of the vertical
wind variation such as  
                             APPENDIX A

     During the early  stages  of planning for the Workshop, EPA per-
sonnel in the Meteorology and Assessment Division in Research Triangle
Park began preparing scenarios  on various field study approaches.
The first "strawman" plans  were prepared by Mr. George C. Holzworth,
Chief, Geophysical Research Branch,  and Dr. William H. Snyder, Chief,
Fluid Modeling Section;  Holzworth's plan addressing a  full scale
measurement program and  Snyder's plan a small  (100 m) hill experi-
ment.  Subsequently, both  scenarios were combined into one "straw-
man" plan and distributed  to  the Workshop participants  for their

     A third document  was  prepared by Dr. Robert G. Lamb of the EPA
Atmospheric Modeling Sciences Section immediately prior to the Work-
shop.  It was distributed  during the Workshop for consideration with
the other scenarios.

     These "strawman"  plans are presented below in the same format
as distributed to the  participants for use as reference material to
the panel statements and recommendations presented in Section 5.  They
should be considered strictly in light of their original intent,
namely to provide the  panel members with specific ideas and sugges-
tions for deliberation and not as documents intended for publications
which have been subjected  to  editorial reviews and corrections.





     Mathematical models of atmospheric dispersion are relied upon
heavily to evaluate compliance with air quality standards and preven-
tion of significant  deterioration.  Although the economic consequences
of model results  can be very large, it has been difficult  to demon-
strate that available models have a reasonably high degree  of relia-
bility, especially  in regions of complex terrain.  This chronic prob-
lem is becoming acute as energy development and utilization  expand in
mountainous areas.   The total problem is overwhelming, not  only from
its complexity of meteorological conditions  and  terrain configura-
tions that occur, but also from the expense  of obtaining  adequate
experimental  data.

     The Meteorology and Assessment Division (MD) of EPA's Environ-
mental Sciences Research Laboratory has been  charged by the EPA with
the development and execution of a five-year, multi-million dollar
program designed  to produce atmospheric dispersion models that are
applicable to large sources in complex terrain and that have a demon-
strated higher degree of reliability than existing models. Current
(preliminary) plans  for carrying out this charge are contained in this
document, which will be presented to a Workshop  of invited experts
during July 16-19, 1979.  The Workshop is directed to make recommenda-
tions for improving this plan.   Some components of the program plan
have been adopted from the recommendations of the ERDA Workshop on
Research Needs for  Atmospheric Transport and Diffusion in Complex
Terrain (Albuquerque,  1976).


     Reliable mathematical formulation of transport and diffusion of
atmospheric pollutants has proven to be an extremely difficult task.
For example,  for  individual plumes emitted  under  the relatively
simple and optimum situation of flat terrain and steady meteorological
and emission  conditions, model validation of ground-level, maximum,
one-hour average  concentrations at downwind  distances to several
kilometers is generally within a factor of two.   But for complex


terrain settings, where many large  individual sources are  locating,
simulation model results sometimes are not  within a factor  of ten of
measured concentrations.  This  happens because of (1) the distortions
in air flow, (2) the distortions  in turbulence  that occur in  the
vicinity of terrain obstacles  of  all sizes,  and  (3) because terrain-
level concentrations are highly sensitive to the height above under-
lying terrain of the maximum concentrations in  the plume  (i.e., at
plume center line).  These three  terrain effects  are basic to the
overall problem.

     The first basic effect of irregular terrain on atmospheric  dis-
persion (i.e. , transport and diffusion)  deals with the transport,
knowing where the plume is located  in three-dimensinal space  and
time.  While it is obvious that air must go around or over  obstacles
(the latter typically during stable atmospheric conditions and the
former more readily during unstable/neutral conditions),  terrain
features also commonly  influence  the local  circulation through the
diurnal cycle of heating and cooling that  occurs  at the ground-air
interface.  During daytime, upslope flow is enhanced over sun-facing
terrain and downward motion is favored over shadowed areas; during
non-cloudy nights, downslope flow is enhanced over elevated terrain
in association with the development  of strong temperature inversions.
Under weak large-scale  flow conditions these  ground-based flows,
which vary in depth from tens  to  hundreds of meters, induce counter-
flows aloft.  With moderate large-scale  conditions the flow aloft
resembles that of the large-scale,  and with sufficiently strong
large-scale conditions, the low-level,  thermally-induced  flows are
likely to be overwhelmed or markedly modified  by  the  large-scale
flow.  In addition, during certain  conditions  with critically  fast
winds, terrain features can induce  aerodynamic effects which distort
the usual three-dimensional flow  in the vicinity of  the terrain

     The second basic effect of irregular  terrain on  atmospheric
dispersion concerns the extent to which turbulence and diffusion are
altered from their values over  uncomplicated terrain.  Recent limited
investigations in mountainous  regions have demonstrated  that  the
Gaussian diffusion parameter values,  which are  often expressed  as a
function of the Pasquill-Gifford  stability classes, are  generally
larger over complex terrain  than over flat terrain,  especially
during stable conditions and at relatively short  downwind distances
from the plume source.  But these differences  are not necessarily
in the same proportion  for the horizontal  and  vertical components
of diffusion.  The appropriate diffusion parameter values likely
depend upon the details of the complex terrain, not only over the

terrain beneath  the  plume  but also upwind of the plume source.  Fur-
thermore, the diffusion  parameter values are expected to vary with
height above the terrain,  at some level decreasing to the  corres-
ponding values for flat  terrain.

     The third basic effect  of irregular terrain on dispersion is in
reality a combination of the first two; it concerns the small-scale
features of plume interaction with a terrain obstacle in the immedi-
ate vicinity of  the  obstacle surface;  it involves transport  and
diffusion, but for practial  purposes  at some  close distance  of
plume approach to obstacle surface the transport becomes indistin-
guishable from diffusion.   This effect is particularly  important
because of the frequency with which plume center lines (where con-
centration gradients are relatively large) abruptly approach terrain
obstacles.  For  example, a fundamental issue among modelers is the
extent to which  plumes,  that are  well  above the ground where  they
are emitted, interact with higher terrain at downwind  locations.
Various models (e.g.,  Valley, Cramer,  ERT) that have been adapted/
developed for use in complex terrain  handle this situation by main-
taining the plume center line at  1) a  constant height  above  sea
level, or 2) a constant  height above  the underlying terrain,  or
3) a variable height above the terrain  that is some fractional value
of the height difference  between the terrain at the source and beneath
the plume trajectory;  the  use of  these techniques usually  depends
upon atmospheric  stability.  For the case of a plume within a tempera-
ture inversion,  technique  (1) results in relatively very high concen-
trations, technique  (2)  ignores  the  terrain,  and technique  (3)
produces intermediate results.  The technique that is most appropriate
remains controversial because adequate,  full-scale field measurements
have not been made.

     Some additional  questions that may be posed about terrain effects
on dispersion are:

      1.  What are the maximum concentrations on a terrain obstacle
          that is in the apparent path of and at a higher elevation
          than a plume embedded in an unstable or neutral layer,  with
          or without an  inversion aloft?

     2.   How do terrain features affect "diffusion coefficients",
          a  and  a ?
           y     z

     3.   In what manner does complex terrain affect mixing heights?

     4.   How does complex terrain affect plume rise?

Answers to those questions are  likely  to  depend upon the wind fetch
over irregular terrain, the  details of  terrain  features  (e.g.,
variously inclined hills and ridges, individually and in combination),
atmospheric stability, wind  speed, and plume  height with respect to
that of terrain features.

     Clearly, the total problem of understanding and modeling atmos-
pheric transport and diffusion  over  complex terrain is  extremely
difficult, but not unsolvable.   With the resources that are emerging
to support such a research program and the wisdom of the scientific
community, we believe  that a very significant impact on the problem
can be achieved over the  next few years.

     At this time it  seems  inappropriate to tackle the total problem
in detail, but rather to  focus  on modeling individual phenomena.  In
this approach each phenomenon modeled may be viewed as a module of a
Mathematical Air Quality  Assessment System (ultimately, it would be
desirable to have a single  equation appropriate to all phenomena
modules, but such an  approach here  appears premature).

     As its first priority  module the TEB proposes to model the one-
hour-average, ground-level  concentrations that result from plume
impaction on elevated terrain.   More specifically, we mean "fanning"
plumes  (i.e., within  a  temperature  inversion)  that encounter a
terrain obstacle(s).  This  phenomenon  has been difficult to model
satisfactorily and has  occurred often  in assessing the satisfaction
of air quality requirements.  The  focus is on maximum terrain-level
concentrations since  typically  they occur relatively closer to
pollution sources than  lesser concentrations,  and therefore  are
easier to study and model.   The model  that is to be developed must
have demonstrated reliability and  specified applicability; it must
be reasonable to apply  in terms of  computer resources and required
meteorological input  information.   However, because meteorological
conditions are more variable over  complex than flat terrain, it is
likely that for a given degree of reliability,  complex terrain models
will require more meteorological input than comparable flat terrain
models, and than currently  is available in most real situations.

     We propose to develop  this modular model from the results of
field experiments which are essentially on two scales and which are
briefly described here:

     1.  A small hill  about 100 meters high in otherwise uncompli-
         cated terrain would be  highly instrumented  to measure
         meteorological  variables and the  concentrations from  a
         movable tracer source.  This experiment essentially would
         expand into the real  atmosphere the scale  of  laboratory
         fluid modeling that has been done by Hunt  et  al.  (1978).

     2.  Full-scale field measurements would be made of  meteoro-
         logical variables and pollutant concentrations from an
         operating power plant in complex terrain.  Tracer studies
         on terrain obstacles  in the vicinity of the power plant
         would be employed also.  This experimental strategy is
         intended to provide a direct  link between  idealized experi-
         ments and actual operating situations.

     It should be emphasized here that model production is the ob-
jective of this effort.   While the required model(s) clearly cannot
be developed with inadequate experimental information, the necessary
experiments must be kept  within bounds  that assure adequate resources
for model development  and evaluation.   We believe that our modular
approach to the total problem provides a means of achievability within
available resources and it provides a logical basis upon which to
build if additional resources  develop.

     Since model  development is paramount in this effort, the modelers
must be active throughout the project.   They must specify requirements
for measurements early in planning experimental operations; they must
be involved in archiving  and documenting the data to assure  that
their requirements are being met; and they must be immediately in-
volved in the experimental data analyses in order to  thoroughly under-
stand the results for  effective incorporation into future experiments
and inclusion in the mathematical models that are under development.

A.   Field Study Design

     Experimental field  studies will  be carried out in three designs
in order to quantitatively  establish  the process of plume impaction.

     1)   Small Hill Tracer Study.  This study will provide a tie-in
between the real  atmosphere and the laboratory, scaled, fluid modeling
studies that have been done by Hunt et al.  (1978).  Meteorological
conditions and the impact  of an inert tracer plume will be measured
on a three-dimensional hill, no higher than 100 meters and located in


otherwise flat terrain.  The tracer (e.g., ethane,  SFg, etc.) will be
dispensed from a portable tower or tethered balloon.   About five 150-
meter towers, instrumented  at several levels, will  be placed around
the hill and a shorter  tower will be positioned on  top of the hill.
All monitoring data  will  feed directly to a central  minicomputer for
immediate analysis and  real-time graphical display  so that  source
location, height, and strength can be altered to achieve  the desired
impaction characteristics.   This study is designed  to enhance the
acquisition of data  by  simplifying the logistics and terrain com-
plexities; it differs from  the laboratory studies of Hunt et al. by
necessarily including the turbulent boundary layer  next  to the hill
surface that occurs  in  real situations.

     Meteorological  measurements would be made of  the three-dimen-
sional wind, temperature,  and other variables that  the modelers may
specify.  It is estimated that tracer samples will  be required at
about eight levels on the hill.

     The hill size required for this experimental  study and  for
general applicability of the results is not believed  to be important,
except the hill should  be completely immersed in a very stable layer,
the hill should be large  with respect to the surface boundary layer
depth, and the ratio  of  hill base-diameter to height should not exceed
eight.  Theoretically,  the flow structure will be dependent upon the
Froude number
where U = wind  speed,  h = height, g = gravity, and T = temperature.
If the vertical  temperature gradients and  velocity  profiles  are
linear, which frequently occurs, the Froude number is independent of
hill height.  Thus,  the entire range of  atmospheric stability varia-
tions may be obtained  by performing the experiments on a single hill,
one perhaps even smaller than 100 meters high.

     We believe  that a large and adequate amount of experimental data
can be obtained  during about three months of field operations after
the equipment is set up.

     2)   Full-Scale Plume Study.  This study  is  designed to link
the idealized,  small-hill, experimental results with those focused
on the plume of  a large operating power  plant.  The principal pollu-
tants to be measured will be S02 and total particulates,  including
sulfates, which  will permit calculation of the sulfur budget.  SOp
transformation  over  travel t^mes up to a few hours, however, is not
expected to be  significant.  While pollutant  transformations  and


depletions are important  factors  to  be  included in comprehensive
models, they need not necessarily be studied  in complex terrain,
and are under study elsewhere.   The  measurements of total  par-
ticulates and particle-size  distributions in  the plume will  be
especially useful in conjunction  with lidar measurements of plume
configurations.  Measurements of  meteorological variables,  S02 and
particulate concentrations will be made from  ground-level and aloft
through the plume, using  sophisticated  (but currently available) and
conventional sensors carried on mobile and fixed platforms as neces-
sary to define plume configurations  and meteorological conditions.
For ease of operation it  is desirable that potential plume impaction
terrain obstacles be relatively close to the power plant,  preferably
within 25 kilometers.  Candidate  power  plants for this full-scale
experimental study should be screened carefully  for the desired
terrain features and meteorological  conditions.  In addition, the
operators of the power plant(s) selected for  study must be  willing
to cooperate completely since pollutant emission  rates, effluent
temperature and volume-flow  rates, other chimney/plant character-
istics, and meteorological conditions in the  immediate vicinity of
the plant must be  known  continuously  during  field measurement

     S02 may be measured  remotely by the Barringer correlation
spectrometer method and directly  by readily available, EPA reference
methods; particulate aerosols can be measured indirectly by lidar
and directly by light scattering  (nephelometer) as well as  by con-
ventional filtering techniques.   Although accurate measurements of
particulate concentrations over short-time intervals are difficult,
the main reason for requiring them is for tie-in  to lidar measure-
ments of plume configuration.

     Meteorological measurements  will require several towers ex-
tending to about 50 meters.   Besides the usual  measurements of trans-
port and turbulence, the fluxes of  heat,  momentum, and moisture would
be determined.  Indirect  measurements of wind fields would  be made
by doppler acoustic or laser techniques.  Frequent double-theodolite
pibal and temperature soundings would be required.  Consideration
would also be given to the use of  acoustic sounders to record growth
and decay of nocturnal temperature inversions.   Several aircraft
would be used not only for plume sampling and meteorological measure-
ments, but also for servicing and transporting mobile ground-based

     This full-scale study will be  conducted intensively during four-
to six-week periods of at least one  winter and  summer season and at

other power plants in succeeding years as necessary and dependent on
available resources.

     In conjunction with  the  full-scale plume measurements,  tracer
studies will be conducted in  order to optimize the measurements of
impaction on terrain obstacles  in  the vicinity of the power plant.
These experiments will also be used to resolve complex, site-specific
questions about modeling  assumptions and to broaden the  range of
applicability of the results.   For the most part we expect these
tracer experiments to be  carried out when transport conditions are
inappropriate for full-scale  plume measurements, although  in  some
situations they may be extremely useful in augmenting the full-scale

B.   Laboratory Simulation

     Careful consideration needs to be given to the further use of
laboratory scaled  (physical)  modeling techniques to complement the
field studies and model development.   This relatively economical  tool
can provide essential detail and data for correlation with and exten-
sion of computational model development, field investigation, and
definitions of basic aerodynamic characteristics.  For example, it
would be extremely useful to  model specific terrain features in the
vicinity of the plant(s)  selected for study,  as well  as in the
vicinity of other plants.  Such laboratory modeling would  also be
used in developing mathematical modules of other important plume
phenomena such as  "fumigation"  and "trapping".

     This effort could be performed at ESRL's Fluid Modeling Facility
at Research Triangle Park, especially in view of that group's contri-
butions and on-going interest in  the overall problem as well as the
administrative convenience of being co-located with the MD.

C.   Potential Field Sites

     From practical considerations it will be desirable to conduct
the small hill tracer  study in the vicinity of the power plant
selected for full-scale  study,  although this approach should not be
pursued to the extent  of  compromising the basic requirements for the
small hill experiments.   In any case, it is believed that an appro-
priate site can be  found  without  great difficulty.

     For the full-scale  plume study, the specific details of the
experiments would  be designed around the power plant that is selected
for study.  A prime factor in this selection must be the willingness
of the plant operators  to cooperate.  At the present time, because


of anticipated  energy resource development  and utilization in the
West and because  of  presently operating plants that are relatively
isolated from one another, a western plant  is favored for the initial

     As points  for discussion, two possible power plant sites are
described.   However,  their potential for plume  impaction on elevated
terrain should  be studied further.  The Navajo Power Station near
Page, Arizona,  is an example of a power plant on a plain with nearby
prominent  terrain features.   With a capacity of 2250 MW, Navajo has
three 236-meter stacks that emit about 200 tons/day of 302.  The plant
elevation  is 1300 meters MSL,  and there is  a variety of terrain ir-
regularities within  30 km.   At their closest point about 22 km west,
the steep Vermillion Cliffs and the plateau  behind them rise to around
2000 meters; the  cliffs trail  off to the southwest and northwest for
10-15 km.  There  are numerous singular peaks fairly close  to  the
plant, e.g. , Lechee  Rock reaches 1800 m at 7 km to the southeast and
Tower Butte  is  almost 1600 meters in elevation at 10 km to the north-
east, as well as other obstructions at greater distances.  The terrain
in this region  is so rugged that many locations cannot be reached by
surface vehicles.   This site has good potential  for studying plume
impaction as well as other types of plume interactions with individual
terrain features.

     The Mohave Station, on the Colorado  River near Bullhead City,
Arizona, is  an  excellent example of a plant  in  a very deep and broad
valley.  This plant has a capacity of 1500 MW  and emits about 44 tons/
day of SOg from a single 150-meter stack.   The plant elevation is 200
meters MSL and  the terrain generally slopes up to the east and west
of the north-south Colorado River, reaching 900-1200 meters within
15-25 km.  There  are also numerous smaller  terrain features within
30 km of the plant.   The weather at this  site is  dominated  by a
diurnally varying mountain-valley circulation, which could serve as
the focus for field  experiments.  With suitable  large-scale flow,
aerodynamic  effects  on the plume are expected.  During summer, tem-
peratures well  above 100°F are common at  Mohave  and likely would
cause some problems  for field operations.

     It should  be mentioned that both these sites are in the southern
Rockies where moisture is sparse so that  precipitation depletion of
the plume and SOg tranformation (as enhanced by high humidity) would
be small.  Furthermore, the infrequent occurrence of precipitation
is highly desirable  for field operations.

     The question arises whether to conduct the  complex terrain plume
study intensively at only one location for  the study duration,  or


whether to progress  to a second (and maybe  third)  site based on
terrain peculiarities.   While it would be  highly desirable to operate
at two or three  different sites in order to  increase the  general
applicability  of the models developed,  resources might not be suffi-
cient to allow this  portability at the anticipated  funding level.

D.   Model Development and Testing

     For emphasis,  it is mentioned again that  the models to be  de-
veloped must be  reasonable to apply  in terms of  required computer
resources, input meteorological and plant operations data, and other
information, and the models  must have demonstrated reliability.  Since
production of  mathematical models is the  basic objective that drives
this project,  the modelers must be active in all phases.  They must
prescribe the  initial modeling approach and the required input vari-
ables (including any new but practical concepts); they must partici-
pate in field  study  designs so as to build upon earlier results; they
will be responsible  for field data analyses/interpretation and  for
incorporating  them into the modules  of the air quality assessment
system that they are developing.  The models will be tested for sensi-
tivity to dependent  parameters, validity of calculated concentrations
and transferability  to other complex terrain  settings.  In addition,
comparisons will be made to  "off-the-shelf" models (e.g., EPA's Valley
and CRSTR models and Environmental Research and Technology's variable
height model), as well as to other models  under development,  in order
to demonstrate modeling accomplishments.

     At this point in time it seems unlikely  to expect the emergence
of basic new modeling concepts.  Rather, the Gaussian distribution of
time-averaged  concentrations within the plume  is expected to persist,
but with distortions and modifications,  due  to terrain, somewhat as
modeled now but  supported by experimental data.  Perhaps the concen-
trations can be  calculated in successive phases of  dispersion as
effected by elapses/types of underlying terrain.  For example,  plume
impact ion on elevated terrain is likely to be  a function of the maxi-
mum terrain-level concentrations within  the  plume just  before it
significantly  interacts with the terrain.  Thus, the plume centerline
concentrations could be calculated in  the first phase  much as in
the usual manner and the terrain-level,  impaction concentrations in
the second phase by  consideration of  the terrain characteristics.

     Because of  terrain effects, it  seems clear that considerable
effort will be required to  adequately model plume paths, particularly
at greater distances from sources.   It also  seems likely that more
input information will be required to satisfactorily apply the models
than is normally available in complex  terrain.   In  terms of  input


data, consideration  should be given to using them to generate reli-
ability factors in the model applications.  For example,  wind fluctua-
tion and/or other  meteorological measurements, taken over appropriate
averaging times,  may  be  indicative of the reliability of  the estimated
plume location as  well  as the diffusion rate.  Diffusion rates, as
functions of terrain features,  height, and stability  probably will
have to be determined experimentally as in the past.

E.   Complex Terrain Modeling Workshop

     During July  16-19, 1979, a Workshop (conducted under an EPA con-
tract with North  American Weather  Consultants) will be held in
Raleigh, North Carolina for the purpose of commenting and developing
further recommendations on .the program plan presented  in this docu-
ment.  About 45 participants have been divided into five panels:

     1.   Model Development and Analyses

     2.   Model Evaluation and Application

     3.   Experimental  Design

     4.   Measurement Techniques

     5.   Data Management and Quality Assurance

The final report  on  the Workshop recommendations is due  from the con-
tractor in September 1979, for subsequent publication and  distri-
bution.  An initial  draft  of the document is expected at the close of
the Workshop.

F.   Schedule and  Budget

     A schedule of research milestones appears on the following page.
Notice that the modelers  will be active throughout the project.  The
small-hill impaction study will be conducted at  only  one  site, as
presently conceived,  although such studies of other plume configura-
tions might be warranted  at a later time.  Full-scale plume impaction
studies would be  continued as necessary, although  we  believe that
after one year sufficient progress will have been  made to focus on
other modules  (plume phenomena) of the assessment system.  The first
year's (FY-80) resources  are expected to produce fundamental results
based on the small-hill tracer impaction study.   Continuation into
the full-scale plume measurements will depend upon continuing re-
sources.  Assuming funding of approximately 2 million dollars per year
for three years  (beginning in FY-80; to be expended over about five


                          IN COMPLEX TERRAIN

                   (ASSUMING RESOURCES BEYOND FY-80)




                                         MODELING: DO
APRIL 1980
           JAN 1980-DEC 1980

                  AND OTHER MODELS
                  JUN 1981

           JUN 1980

           CONDUCT FUL
           JAN-FEB 1981

           JUL-AUG 1981

           JAN-FEB 1982

                  PUBLISH  INITIAL
                  APR 1982

           JUL-AUG 1982

                  DEC 1982


years), we believe that  significant progress in the development of a
complete model assessment  can be demonstrated.

G.   Management and  Implementation

     Responsibility  for  directing this complex-terrain,  plume-
modeling study has been  assigned to  ESRL's Meteorology and Assess-
ment Division.  A high-level  steering committee will be formed to
provide overall guidance toward program goals, to monitor progress
at frequent intervals, and to provide a liaison between the program
and the user community.  In addition, an in-house working group com-
posed of modeling and  measurement subcommittees will be available
to MD personnel to help  assess the validity of the modeling effort
and to assist in reviewing technical  proposals and reports.

     As presently  foreseen the  entire program plan will be carried out
under contract, probably with a prime contractor responsible for the
overall modeling effort  and with  provision  for subcontracting.
Monthly progres reports  from the contractor will be required and will
form the basis for  reports/presentations to keep the  steering
committee informed of  program accomplishments and immediate plans.

     Although this mo del-development program plan has focused on the
important plume-dispersion phenomenon of impaction on  elevated
terrain, it is appropriate to point out for completeness that models
for other plume phenomena  may be developed through the same basic
approach; that is, through laboratory  scaled physical modeling (as
appropriate), tied in with full-scale  plume measurements.

     Data collected in  the full-scale  field study will be useful for
this purpose.  Reference to the  schedule shows that the program is
designed to implement the small scale hill study first and to initiate
detailed planning for the  full scale  field study at the same time.
The full scale field study will  be initiated in late FY-80 and  will
overlap the conduct of  the small scale studies.

     The site selected for the full scale field study will be selected
to maximize the opportunity to incorporate the findings of the small
hill study and to maximize the opportunity to collect data useful for
developing other modules of the  final  model equation.

     Two major areas of  uncertainty by the presence of complex terrain
are the transport wind  field which may vary significantly over small


distances, particularly in the vertical direction and an altered tur-
bulence field which may drastically  affect the dilution rates.  Thus,
the long-term goals of  the  modeling program must consider a satis-
factory description of  the  transport wind and turbulence fields as
well as the joint  frequency of occurrence of a wide range of meteor-
ological conditions and topographical configurations.  The frequency
with which certain events occur,  are of course pertinent to  the
question of whether or  not the Air Quality Standards are violated and
must therefore also be studied.  A separate document has been prepared
by Dr. Robert Lamb which addresses  the frequency question and will
be available  to  participants at the Complex Terrain  Workshop.



                         DR.  ROBERT G. LAMB

     Regardless of whether one is concerned with flat  or complex
terrain, the objective of air pollution modeling efforts is to develop
a means of predicting the second highest concentration  that will occur
in any year from a source  of  given location  and specifications.
Actually, no one can say what the highest or second  highest concen-
tration will be at any  site in any future year because  the physical
processes that control  concentrations,  principally the  weather,  are
not deterministic.  At  best one can estimate the probability that a
particular concentration will occur based on projected  source emis-
sions and historical weather  data.  Thus, in the discussions that
follow, we will view the pollution modeling problem from  the pro-
babilistic standpoint.

     One reason for doing  this is to get away from  the prevalent
notion that understanding the dynamics of plume impaction on hills is
the key to the complex  terrain modeling problem.  We will  discuss
below two other equally important aspects of the problem  that must be
resolved before the above  stated goal  of diffusion  modeling can be

     Another motivation is to illustrate the magnitude of the overall
modeling objective.  There are 8760 hours in a year so the task of
estimating the second highest hourly averaged concentration in a year
is essentially that of  finding  the value C2  that  satisfies  the
               p(C)dC   ==
where p(C)dC is the probability that the hourly averaged concentration
at the given site  is  in  the range C to C + dC.

     It is evident  from  this expression that the stated objective of
pollution modeling  is an ambitious one in that it requires a rather
precise knowledge  of  the form of the upper tail of the concentration
probability density p(C).   Under the best of conditions  they  are


limited to the accuracy with which the probabilities of  the extrema
of any process can  be  estimated.  Consequently, we should  devote part
of any modeling  effort to the question of whether, given the inherent
uncertainties with  which we can describe the phenomena  that effect
pollutant concentrations in complex terrain, we  can ever achieve a
model of the second highest concentration that  provides estimates
reliable enough  to  form the basis of highly costly emissions control
procedures.  Stated another way, we should compare the magnitude of
model uncertainties,  translated into dollar costs of control equip-
ment, with the cost of alternate methods of estimating  the second
highest concentration, such as long-term tracer monitoring studies
conducted at prospective plant sites.   The results of these types of
analyses might lead to the abandonment of complex terrain modeling

     In any case it is desirable to determine as soon as possible
(if it is determinable at all) the inherent  limits on the predict-
ability of the probabilities of concentration extrema in complex
terrain.  This knowledge gathered early in a multi-year model develop-
ment program could  guide the redesign  of those  studies  planned for
subsequent years and thereby circumvent the expenditure of  large
amounts of money and manpower pursuing goals that are unattainable.
Thus, one criterion for the design of  a long-term complex terrain
modeling program should be that the information  required to analyze
the predictability  question be gathered during the initial phase of
the study.

     The remaining  design criteria can best be formulated by examin-
ing the information needed to solve the equation  that gives the pro-
bability density p(C).

     For this purpose it is convenient to collect the physical pro-
cesses that affect  transport and diffusion into several groups as

     Firstly, we isolate the geostrophic (or synoptic scale) meteoro-
logical conditions over the  given site at a given time.  The important
variables are the wind speed and direction, temperature and dew point,
all measured at  the geostrophic level (say 700 mb); cloud cover; and
elevation of the subsidence inversion base.  We will denote this set
of variables by  the symbol  G and refer to it often in the  probabilis-
tic analyses as the "event"  G, to signify the occurrence of a specific
set G of these variables.

     Secondly, we  isolate the micro-mesoscale meteorological condi-
tions at the site.   The important parameters here  are the three-
dimensional flow and temperature fields  in a layer roughly  1 km deep
based at the source elevation and extending over the entire horizontal
region in which significant concentration levels are likely  to occur.
We will represent  these fields by the symbol M and refer to  them
occasionally as the "event" M.

     Thirdly, we consider the plume rise  and buoyancy generated plume
spread processes.   The three-dimensional coordinates  of  the  plume
centerline; the plume's width, depth and material content as  functions
of distance along  the centerline; and the  frequency and lateral extent
of plume meander will jointly be denoted  by the symbol (and  event) P.

     Finally, we have the processes that govern plume impaction.  We
are not interested in the details of these processes themselves, but
rather with the ground-level concentration they produce for given P.
Thus, we define the event C as the occurrence at the given  site of a
particular concentration value, say C.   The impaction  processes are
implicit in C.

     The four components of the problem we have  just  defined  are
interlocked: a particular set G of geostrophic conditions  occurs at
the site; these acting in concert with physical  properties of the
local terrain give rise to a particular micro-mesometeorology M; in
this flow the power plant emitting material at a given  rate and tem-
perature from a stack of given height and diameter produces a plume
of specification P;  boundary layer processes bring this plume into
contact with the ground causing a concentration C.   Thus, the task of
estimating the probability that a particular concentration C will
occur at some point is simply that of determining  the total  pro-
bability that all  combinations of these four events that produce
the value of C will occur.

     The probability that M, say, is in the range  N to N + dM  is
p(M)dM.  Since M is dependent on G, p(M)dM is different  if we are
given that a particular G has occurred.   We represent this condi-
tional probability by p(MJG)dM.  Similarly, we can define the condi-
tional densities P(PJM) and p(C|p,M).

     Using these functions and basic statistics theory, we  find that
p(C) that enters in Eq. (1) is given by

      p(C)  =  |/p(C|P,M)p(P|M) / p(M|G)dGdPdM.          (2)

     Equations  (1)  and (2) are the basic form of  the  "second highest"
concentration model that will serve  as  the focal point for the dis-
cussions that follow.   We wish to emphasize here  that (1) and (2) are
not an esoteric set of  equations of academic value only.  Rather, they
embody in highly  condensed form all  of  the physical processes that
are believed to be important in the complex terrain dispersion problem
and therefore any model that is to yield reliable  estimates of concen-
tration extema  probabilities  is reducible to the  form of (1) and (2).

     In order to  provide a better understanding of the physical mean-
ings of each of the probability kernals in (2), we shall discuss each
below.  From these discussions will  emerge a picture of many of the
current needs in  complex terrain modeling.
A.   The  Impingfeaient Kernel, p(C|P,M)

     Recalling the definitions of P  and M,  we see that p(c|P,M) is
essentially  a relationship among the concentration at some ground-
level site,  say a hillside,  and the height, width,  depth, and material
content of the plume and the ambient flow speed, direction and tem-
perature  stratification.  It is precisely this relationship that has
been the  subject  of nearly all the  laboratory and field studies of
complex terrain dispersion that have been conducted to date.  In keep-
ing with  the established terminology,  we shall  call  p(CJP,M)  the
impingement  kernal because it embodies only the processes that bring
a given plume into contact with the  ground.

     Over flat terrain, which incidentally is also within the scope
of applicability  of (1) and (2), this kernal is frequently assumed to
have the  conventional Gaussian form.  In this expression, P is re-
presented by the  effective source height, a ,  a  and source emission
rate Q; and  M is  represented by the  wind speed u and the atmospheric
stability, that establishes the magnitudes of a  and a  .   In this
instance,  the mean flow is everywhere  parallel to the ground and hence
material  impinges on the surface only as a result of the action of
vertical  velocity fluctuations, or eddies, in the turbulent boundary
layer.  It is the universal  character of steady-state turbulence over
a flat surface that is manifested in the universal Gaussian expression
assumed for  p(C|P,M) in smooth terrain.

     In complex terrain the mean flow is not everywhere parallel to
the earth's  surface and therefore it  can act in conjunction with tur-
bulence to transport plume material  to the ground. In this case the
form of P (C|P,M) is influenced strongly by the size and shape of the
hill, by  its surface roughness, and  possibly by  the  nature  of the


terrain just upstream of the hill.  It is  speculated that if  time and
length variables  are  non-dimensional by  the proper combinations of
flow variables and characteristic length scales of the hill, universal
forms for the  relationship p(C|P,M) exist that will be applicable in
complex terrain just as the Gaussion plume  formula is assumed  to apply
over flat areas.   However, if we consider  in detail the physical pro-
cesses that affect concentrations on the  side of a hill, we  see that
previous laboratory studies are not adequate in themselves to estab-
lish the true  form of p because they do  not account for the effects
of turbulent boundary layers.

     No matter how large  or small a hill may be  and no matter how
stably stratified the flow may be, there  exists a turbulent  boundary
layer adjacent to the hill's surface.  The turbulence is generated
in part by the shear  in the. velocity field; partly by obstacles such
as boulders, trees, etc.  that  may dot  the surface;  and partly  by
heating and cooling of the hillside.   The last process is  probably
very important on hills the size of those that are likely to exper-
ience plume impingement.   (Considering the fact  that power plant
stacks are typically 200-300 meters high and that plumes commonly rise
300-500 meters in stable  conditions, we estimate that the character-
istic hill size of interest is 500-800 meters).  On the sunlit side
of a hill, heating generates upslope flows that produce a convective
boundary layer that increases in depth from the base to the top of the
hill.  Conversely,  on the shadowed side and at night, surface cooling
generates a downslope flow that is  deepest at  the  base of  the hill
and very shallow  at the hill top.   On  the windward side of a hill
this downslope flow would  accentuate the surface  layer wind shear
and possibly enhance  turbulence levels.

     Furthermore,  hills several hundred  meters tall usually  have
smaller hillocks  superposed on them and  ravines cut in their sides.
These features generate turbulent wakes  that are  shed and  advected
along the hill's  surface  to further augment the depth and intensity
of the turbulent  boundary  layer.

     The essential point here is that when  a plume impinges on a hill-
side, it must  travel  through this turbulent surface layer  to reach
the ground.  In the process plume material is diluted by mixing with
clean air in the  boundary  layer; and depending on  the character of
the turbulence in the surface layer, for example, the extent  to which
it is composed of wake turbulence,  the plume material may  meander
across the surface of the  hill and  thereby produce quite  low time
averaged concentrations.

     Figures A-l and  A-2 depict the processes we have just described.
The main purpose of these figures is to illustrate that the process of
dispersion within the  immediate environment  of the hill is practically
identical to that  of  plume fumigation from a  stable layer  aloft.

     They also  illustrate  that concentrations at the surface of the
hill are dependent upon the depth of the hill's boundary layer (HBL)
at the point of  plume entry, the intensity and  scale of turbulence
in the HBL, the  mean  flow  speed in  the  HBL, and the rate at which
plume material  is  fed into the HBL from the laminar layer above.  The
latter is dependent upon the angle  that streamlines in the  laminar
region make with the  top of the boundary  layer.   Since laboratory
simulations have purposely suppressed boundary  layer formation by
using very smooth  hills and approach planes (they have also  ignored
thermal boundary layer effects), it would seem  that those  studies
cannot produce  meaningful  expressions for  hill surface concentration
values.  However,  they should be able to yield quantitative informa-
tion on the manner in which hills distort the mean steamline patterns
in the laminar  flow regions around them.  Even this  information must
be used with caution  until it is demonstrated that the  turbulent
boundary layer  does not significantly alter the flow in the  laminar

     In summary,  we have argued that to obtain  the functional  form of
the impingement  kernel p(C|P,M) under stable  conditions in  complex
terrain, we require both a  quantitative description of the mean steam-
line patterns  in the  laminar flow regions around hills and  certain
characteristic  features of the surface turbulent boundary layer.  The
specific quantities required are (1) the depth of the boundary layer
as a function  of distance  along the hill, (2) the intensity and scale
of the turbulence  and the  mean flow speed in  the boundary layer as
functions of location, and  (3) the  rate at  which  fluid  from the
laminar region  enters the  boundary layer at each point.  As we stated
earlier, the last quantity  is dependent upon the angle that steamlines
in the laminar  region make with the outer surface of the boundary
layer.  This is information that laboratory and specially designed
field studies  can provide.

     Such studies can also  provide the boundary  layer  information out-
lined above and with  it the diffusion experiments necessary to relate
that information to the rate of dilution  of plumes that enter the
boundary layer and impact the ground.  As we noted earlier, this dilu-
tion process is fumigation-like in nature. Having all this informa-
tion as a function of M, the physical characteristics of the hill
(including its  surface roughness and that of immediate  upstream
areas), and cloud cover and albedo from which we  can  estimate  surface


        Turbulent Boundary Layer

Figure A-l.   Diagram showing flow pattern of stack plume - nighttime.
  Turbulent (Convective)
    Boundary Laye
Figure A-2.  Diagram showing flow pattern of stack plume-daytime.

heat flux, we can formulate  the kernel p(C|P,M)  required to predict
the desired concentration  probabilities.   Later we outline field
studies that can address these  subjects.

     By virtue of its  definition,  p(C|P,M) tak«s into account only
those processes that affect  a plume during its transport across the
surface boundary layer to the ground.   The point where the plume con-
tacts the outer boundary layer,  the plume's dimensions at this point,
its rate and envelope  of meander,  etc., are variables that are in-
cluded in the P event  that we consider next.
     Before proceeding,  we  should add that although  the discussions
above dealt exclusively  with the stable flow case, the same sets of
information are  required for neutral  and unstable flows as well.  It
has been observed  in  the Geysers area of California, for example,
that maximum ground-level concentration occurs under stagnant, con-
vective conditions. This  situation may be typical of sources in long,
deep and relatively narrow canyons or  valleys where all of the stably
stratified flows transport  material approximately parallel  to the
contours of high relief  features.

B.   The Plume Rise/Transport Kernel, p(PjM)

     The event P was defined as the occurrence of a specific, detailed
plume structure  from  the point where material  leaves the source to
the point where  it just  enters  the boundary  layer  of  a terrain
feature.  The probability density p(PJM) of this event is a function
of M and also of the  stack  height and diameter, and  the temperature
and velocity of  the exhaust.  Thus, loosely speaking, p(PJM) is a
plume rise and transport model for complex terrain.

     Over flat regions,  empirical expressions are available for esti-
mating plume rise  under  stable and neutral conditions.  Under these
conditions, it is  assumed that once a plume reaches  its equilibrium
level, it follows  a straight path indefinitely far downwind from the
source.  Neither this assumption nor the flat  terrain  plume  rise
formulas are applicable  a priori to complex terrain.  One reason is
that low-level stable flows in complex terrain  are  not  generally
horizontally homogeneous like they are over uniformly flat ground,
and thus plumes  are often observed to wind along irregular paths and
to meander horizontally.  Furthermore,  in rough terrain regions,
vertical profiles  of  wind and temperature often exhibit extreme vari-
ations with height.   The extent to which these  variations affect
plume rise and spread is not known, but it must be  established in

order to obtain reliable estimates of p(P|M).   In  addition, the magni-
tude and frequency  of plume meander  must also  be determined and
related to M  and  characteristics of the topography.  For example,  the
meander phenomenon  may be due to vortex  shedding  behind large hills
or it may be  caused by "sloshing" of  cold air in  a valley under  the
influence of  the  wind stress exerted  by  the geostrophic flow aloft.
In these cases  it might be possible  to establish  at least bounds  on
the meander magnitude and frequency  based on hill size, flow speed,
valley width, geostrophic wind speed, etc.

     We will suggest field measurements to investigate these phenomena

C.   The Micro-Mesoscale Meteorology  Kernel, p(M[G)

     It has long  been known that the differential heating and cooling
of the sloping surfaces in complex terrain generates local circulation
regimes much  like the differential heating  and  cooling of adjacent
land and water  surfaces gives rise to lake  and  sea breeze circula-
tions.  It is the three-dimensional  structure (speed, direction  and
lapse rate) of  these local flows that is embodied in our definition
of M.

     One of the problems that complicates the modeling of dispersion
in complex terrain  is that M does not normally exhibit the horizontal
uniformity that it  does over flat areas well  inland from large bodies
of water.  In other words, over smooth,  inland  sites the  smallest
horizontal spatial  variations that exist in  flows  have length scales
of several tens of kilometers; whereas, in complex terrain the corres-
ponding scales  can  be an order of magnitude or  more smaller.  Thus,
over flat, inland terrain meteorological data from a rather coarse
network of stations  are adequate to piece  together a reasonable three-
dimensional description of the flow,  i.e.,   M;  and if  sufficient
quantities of historical data are available, the probability density
p(M) can be estimated.

     By definition

      P(M)  =  lp(M|G)p(G)dG,     cf  Eq. (2)              (3)

     In complex terrain the density  of  meteorological stations  is
generally much  to small to determine M.  However, there is sufficient
information to  obtain G and p(G).  This  suggests  that there are  two
avenues of approach to the gathering of data needed  to determine p(M).

     One is to undertake an extensive  study of the physical processes
that govern micro-mesoscale  flows in  complex terrain with the objec-
tive of developing  a  model  of p(M|G)  applicable to  all  types  of
terrain.  The processes  involved are  almost totally  dominated by the
terrain features, which  incidentally  have been  documented by  the
U.S.G.S. with extreme resolution for  the entire country.  This study
would involve field  projects, physical  modeling in the laboratory, and
numerical simulations.   At  this juncture, there  is  evidence  that
a usable model of p(M|G)  cannot be developed.

     The second  approach to gathering  the requisite data  is to deploy
at every proposed site of  a power plant a network of meteorological
stations dense enough to resolve M, and to collect  data for a long
enough period  (at least two years),  to determine p(M). This approach
would be expensive  and time-consuming, and unless  the  measurement
network were designed properly, the information  gathered might not
be useful at any other locations.  One might argue that  if this type
of an approach were taken,  it would make more  sense to bypass the
meteorological measurement  altogether and  to perform  the tracer
studies necessary to  determine p(C) itself.   For example, one could
erect a tall, tower, at least as tall  as the lowest anticipated plume
elevations, and  release  a different  inert  tracer  steadily  from
various levels of the tower.   Automatic syringe  samplers  deployed
over the surrounding  area and collecting hourly air samples on a con-
tinuous basis would provide the information  required to  determine
p(C) directly.   No  aircraft observations or mobile  measurements of
any sort would be necessary.  " The obvious advantage of this method
is that it circumvents the  uncertainties that attend model calcula-
tions and thus it provides  a much more reliable  basis  for making
control decisions.

     The preliminary design, planning,  site selection, etc., necessary
for large power  plants require several years to perform.  Thus, if a
monitoring study such as this one were begun at, say, the three most
preferred sites, by the  time plant construction was ready to begin,
adequate concentration data would have been gathered to determine the
degree of emissions controls required.  One problem with this method
is that a plume  of  passive  tracer material does  not expand as much
under stable conditions  as  that of power plant emissions because it
lacks the buoyancy.  For this reason, measurements of wind and tem-
perature on the  tracer release tower  would be needed to  estimate the
degree to whch buoyancy  would enhance dispersion.

     The purpose of this digression was to point out that there are
alternatives to  modeling dispersion in complex terrain.  We believe

that a critical  evaluation of these various  methods should be  con-
ducted as a part of  the proposed modeling program, weighing the un-
certainties that attend model predictions, translated into dollar
cost of control  equipment, against the cost  of  monitoring studies
where uncertainties  are greatly reduced.  Results of predictability
studies like  those  suggested earlier in this report would be of value
in this task.

     Returning to the discussion of M and p(M), we can view M as the
resultant of  a local,  thermally induced  circulation superposed  on a
terrain augmented geostrophic flow.   In  instances where  the  geo-
strophic flow is weak,  the local circulation will dominate,  and hence
M will reflect the  characteristics of the  local terrain.  Since these
features are  constant,  we would expect that  for this set  of "weak"
geostrophic flows and given cloud cover  conditions and hour and day
of year, there is negligible variation within the corresponding set
of M.  It is  likely  that in many areas the highest ground-level  con-
centrations occur during the "weak G" situations.  Where this is the
case, being able to  describe the local circulation regime and knowing
the probability  of  "weak G" are all that  are  required with  regard to
p(M) to solve (2).

     Another  simple  case is that where the local  circulation is so
shallow that  plumes  are able to break out of it and enter the  geo-
strophic flow above.   In this case we replace p(M) in (2)  with  p(G)
(see also Equation  (3)) and M in p(C|P,M) with G.  Recall  that  p(G)
is usually known.

     In situations where plumes are frequently confined to  the local
flow; i.e., the  layer described by M,  and  neither the terrain nor the
geostrophic flow dominate M, the modeling problem is much  more  com-
plicated.  It is this class of problems in which the highest modeling
uncertainties will exist.


     We have  shown that there are three  basic  components  of  the
complex terrain  modeling problem and  have emphasized that  all three
must be understood  to meet current modeling objectives.  One of these
components, namely  the impingement processes, has already received
a great deal  of  attention.  The other two have  not.

     We have  also emphasized the uncertainties in model calculations,
especially in complex terrain environments, and have stressed the  need
for studies aimed at assessing quantitatively the inherent  limits on
the predictability  of concentration extrema  in such areas.   The


results of this study should be used to perform cost/benefit calcula-
tions to determine whether  there are possibly methods  other  than
modeling that can best  meet existing regulatory needs.

A.   Studies Relevant to the Impingement Kernel, p(C|P,M)

     The major information  required to formulate p(C|P,M) is the

     1.  A characterization of the three-dimensional  streamline
         patterns in the laminar flow region around  hills during
         stable conditions,  expressed in terms of Froude  number, hill
         height and  aspect  ratio, surface roughness, surface heat
         flux, etc.

     2.  Depth G.J the boundary layer adjacent to hills as  a function
         of distance along  the hill, expressed in terms  of mean flow
         speed and stability in the laminar region,  surface roughness
         and heat flux.

     3.  The intensity  and  scale of turbulence in the  boundary  layer
         as a function  of distance along the hill, expressed in terms
         of the same parameters as  (2).

     4.  Mean flow speed in the boundary layer  and fluid transport
         rate into the  boundary layer from the laminar  region, both
         expressed as  in (2).

     5.  A mathematical relationship among the parameters listed in
          (2) -  (4) above and the rate of dilution of  material as it
         moves across  the boundary  layer from the laminar region to
         the ground.

     6.  The range of  variation in  the dilution rate  parameter (see
          (5)) and the laminar region streamline patterns (see  (1))
         resulting from upstream random arrays of hills and depres-
         sions of heights and depths less than  that  of  the  study
         hill under  various conditions  of stability, heat  flux, etc.
          (This information  is needed in the predictability studies,
         to formulate an estimate of the magnitude of  uncertainty
         in model calculations.)  These bounds  would be  expressed
         in terms, say, of  rms height of upstream terrain,  Froude
         number of study hill, etc.

     There have already been a number of  laboratory studies conducted
to investigate  (1).   However,  the applicability of those  results to


complex terain is questionable because the Reynolds numbers  achievable
in the laboratory  are  many orders of magnitude  smaller than those
characteristic of  rough terrain.  Also, previous laboratory  simula-
tions have not included upstream turbulent boundary layers or non-zero
heat fluxes.

     Below we outline  an experiment that can address all  six of the
subject areas listed above and, in addition, provide virtually a con-
clusive answer to  whether the results of  the laboratory studies
mentioned are applicable to the atmosphere.

     The basic experimental design involves  a simulated  hill  con-
structed of flexible material such an canvas, mylar, or other suitable
material stretcned over metal hoops or rods  to  achieve particular
shapes.  The hill  is hung from a cable stretched between  two towers
and, being flexible, it can be  raised or  lowered  to any  height
desired (see Figure A-3).  The hill would be erected on  a dry lake
bed; e.g., Lake   Bonneville, where the ground surface is very flat for
many kilometers  around and stably stratified winds  are frequent.

     Tracer material would be released from  desired elevations and
distances upwind of the hill and sampled on  the hill's surface by
instruments accessible through ports in the fabric that composes the
hill.  All monitoring  and recording of concentrations and flow pa-
rameters would be  performed at a central facility located  inside the
hill that is connected to all instruments by cables.

     The boundary  layer of the flow approaching the hill would be
controlled by raising  fences of fabric panels as  shown in Figure A-3.
These "roughness"  elements could be replaced by or used together with
arrays of small  hills,  perhaps inflatable structures,  to  study dis-
persion on a hill  surrounded by very rough terrain in its immediate

     Positive and  negative heat fluxes could be  achieved on the hill
using perhaps fine water sprays on the exterior surface and gas space
heaters exhausting into fabric ducts on the  inside  hill  surface.

     Instruments to measure concentration and flow variables in the
hill's boundary  layer  could be attached to poles 2-3 meters long and
placed in position from ground-level inside the hill as the  hill is
raised in place.   These poles would be secured to the metal  framework
that supports the  fabric.

     Some of the advantages of this experimental design over  others;
e.g., instrumenting a  real hill, are:



     1)  It provides  a laboratory with complete  control  over hill
         size,  shape,  roughness and heat flux.  For example, the hill
         height could be changed gradually during a single  experiment
         to examine Froude number effects.  Equally important is the
         control possible  over the characteristics of  the turbulent
         boundary  layer of the approach flow.  None of the  parameters
         just  tested  is  controllable with a real  hill.

     2)  Wide  scope of experiments.  All six of  the subject areas
         that  require study to formulate the impingement  kernel can
         be investigated.

     3)  Having the monitoring center located inside the  hill mini-
         mizes  the  logistics problems of servicing  the instruments
         and relaying data to the monitoring site (e.g., cable rather
         that  radio data  transmission is used).   The  flat  terrain
         site  and  the support towers that suspend the hill  facilitate
         measurements of  the approach flow and filming operations.

     The maximum hill sizes and flow speeds used  in the  EPA Fluid
Modeling Studies are  25  cm and 50 cm sec  , respectively.  The fluid
used in water,  v  - .01  cm  sec   .  The hill  size envisaged  in
the present experiment is  25 meters (larger ones  are  possible) and
flow speeds of  4 m sec   are possible.  Thus, Reynolds numbers 100
times larger than  those achieved thus far in laboratory  studies could
be obtained.   Favorable  comparisons of results obtained  over this
range of Reynolds  number  would provide strong  justification  for
continuing and  expanding  laboratory simulations.

     The experiment just described is restricted to studies of stably
stratified flows.  Modeling dispersion under free convective condi-
tions may be possible  using numerical models currently in development.
To apply those  models to  complex terrain, we require  at  least the
following information:

     1)  Probability  density of vertical and horizontal  velocity
         fluctuations over heated hill surfaces  of  various heights
         and widths and  the same information over shadowed surfaces.

     2)  Horizontal scale  and characteristic vertical velocity of
         thermals  as  a function of underlying hill and  ravine sizes.

     3)  The parameters  listed in 1 and 2 as functions  of  sun angle,
         cloud  cover, albedo, and surface slope and height of hills.

     These three  sets of information could be  gathered from aircraft
measurements of the 3-D velocity components taken at various altitudes
above complex  terrain.  The instantaneous data samples would have to
be correlated quite precisely with the horizontal position of the air-
craft so that  the velocities could be analyzed as a function of the
terrain features.

     The case  of  forced convection;  i.e.,  strong surface heat flux
together with  moderate horizontal winds,  might  possibly be modeled
numerically, but  there are no studies of  this sort in progress now.
The theoretical problems to be surmounted in developing such a model
are significant,  and we must conclude that large uncertainties in
concentration  predictions under these conditions will always exist.

B.   Studies Relevant to the Plume Rise  and Transport Kernal, p(PJM)

     The major information requirements  are:

     1.  The effects of vertical variations in wind speed and direc-
         tion,  temperature stratification, and turbulence energy on
         the plume entrainment rates of  heat  and mass.

     2.  The effects of these same parameters on plume meander; i.e.,
         spatial  oscillations in the plume centerline.

     The first studies conducted should be an  exhaustive analysis of
the ability of current plume rise models to predict accurately plume
heights, widths,  and thickness as functions of  travel time in complex
terrain.  Adequate data for this purpose exist in the Mohave, Navajo
and Four Corners  data sets.  These studies should correlate model per-
formance with  the stack height and diameter buoyancy flux, etc.; and
the characteristics of the flow, such as wind shear magnitudes, verti-
cal variation  in  Richardson number,  etc.

     This study would expose the weak points in current models.  For
example, the current methods of parameterizing  entrainment may not be
adequate.  Subsequent field studies using lidar probes of the plumes
that models simulate most poorly could  gather the data necessary to
refine the rise and spread models.  The error levels still present in
refined models would be used in the  predictability studies.

C.   Studies Relevant to the Micro-Mesometeorology Kernel p_(MJG)

     To formulate this function requires a fundamental knowledge of
the processes  that govern the three-dimensional  structure of flows
within the first  kilometer over valleys  in complex terrain.  There


are two complementary  approaches to formulating p(M|G).  One  is
physical and numerical  modeling of the physical processes involved.
The second is an empirical  approach based on extensive  measurements
of key variables in  complex terrain sites of various  types.   The
latter approach is necessary in any event because only  it  can supply
the data required to validate numerical and physical  models.   An
empirical model developed from field data would be used  primarily to
estimate the frequency,  given the climatology of the local geostrophic
flow G, with which a plume  from a given plant might impact a parti-
cular terrain feature;  and  the type of vertical wind shear and tem-
perature stratification profiles, necessary for performing the plume
rise and spread estimates (i.e., P),  that would occur in  these cases.

     We recommerd that physical and numerical flow models  be developed
in the event that empirical formulations prove  to  be unacceptable.

     Some of the questions  that a field program should attempt to
answer are:

     1)  How deep are  valley drainage flows and how does the depth
         vary during the night?  Can the depth  be  correlated  with
         the depth of  the valley, distance down the valley,  etc.?

     2)  Are the speed  and  direction of drainage flows  at any level
         functions of  the slopes of surrounding terrain features of
         a particular  scale?

     3)  Is the temperature stratification within the drainage flows
         strongly dependent on terrain features,  or it is roughly the
         the same from  one  site to another and one hour to another?

     4)  How strong  must the geostrophic flow be at a particular site
         to eradicate  the drainage flow regime?

     5)  During weak geostrophic flows, does the same drainage cir-
         culation regime occur at a given site  (given the same time
         of year, cloud cover, snow cover, etc.)?

     6)  Is there evidence  that wind stress on  the top of the cold
         drainage flow  produces a sloshing phenomenon  that could
         cause plume meander,  and if so, is the sloshing frequency
         relatable to  geostrophic flow speed, valley  dimensions,

     7)  Are the radiation  inversions and vertical wind speed pro-
         files that occur over  high mesas that contain deep gorges
         similar to those found over uniformly flat terrain?

     8)  To what horizontal  distance from the base of an isolated
         ridge does the  drainage flow penetrate?  How does the depth
         vary along the  ridge  face?

     To answer these questions  and to gather the data required for
model validation, we recommend  the following experimental approach.

     1)  Locate a geographical  area that contains terrain features
         of various types within an area small enough for the geo-
         strophic conditions G  to be assumed constant at any instant.
         For example, valleys  of various widths,  depths and lengths;
         mesas with river gorges;  isolated ridges; etc.  (One such
         area exists near Prescott, Arizona.)

     2)  Within the various terrain types deploy a network of instru-
         ments to measure vertical profiles of wind speed and direc-
         tion and temperature  up to about 300 m AGL continuously
         through nighttime  hours.

     3)  Release and track groups of tetroons at various levels with-
         in and above the drainage  flows (these data are necessary to
         check the accuracy of  particle trajectory predictions based
         on fixed site wind observations).

     4)  Monitor meteorological variables on high terrain, make
         radiosonde measurements,  acoustic  sounder probes, etc.

     The experimental setup is  shown in Figure A-4.  Gathering the
vertical temperature and wind  data continuously at numerous sites
would be very costly using  conventional methods.  In the insert of
Figure A-4, we have sketched a system that utilizes a captive balloon
to gather these data at  unmanned sites.  The concept of the design
is based on existing technology,  but as far as is known, such a system
does not now exist.  We  recommend  that some portion of the modeling
effort be devoted to developing low cost means of gathering the data


     The suggested work  is  divided into two programs operated  in
parallel:  One develops  the required model and the other monitors
the model development progress and steers  the overall  effort.


                                                      Tracking Aircraft
                Control Center

(Radio Communication with Unmanned Remote Stations)
                                                Typical Remote Station
  Figure  A-4.   Experimental  design  for studying the  micro-
  mesometeorology  of complex terrain.

3.1  Year 1

     3.1.1  Model Development.

        A.  Select site and construct simulated  hill.  Perform
            hardware  tests and begin preliminary experiments.

        B.  Comprehensive analyses  of ability  of current  plume
            rise and dispersion models to predict  accurately plume
            rise  and  expansion rates (a (t),a  (t)) in complex
            terrain.  Exercise models using all  available  data
            from Navajo, Four Corners,  Mohave, etc.  Correlate
            model errors with magnitude  of wind speed and  direction
            shear, inversion depth,  stabililty,  etc.

        C.  Investigate possible techniques for inexpensive routine
            ground-based measurements of vertical wind and tempera-
            ture up to about 300 m.   Begin instrument development
            program if necessary.

     3.1.2  Monitoring of Model Development Progress.

        A.  Begin theoretical studies of predictability of  second
            highest concentration.

        B.  Investigate alternatives to modeling that  can meet
            regulatory needs, such as long-term tracer  studies.

3.2  Year 2

     3.2.1  Model Development.

        A.  Full scale operation of simulated hill facility. Experi-
            ments to include:

               (1)  Flow patterns around hills of  various shapes at
            various Froude numbers for comparison  with laboratory

               (2)  Develop empirical relations  between plume dilu-
            tion rate and turbulent boundary layer characteristics,

               (3)  Establish the range  of dilution  rates caused by
            random distributions of  upstream terrain  irregularities.

   B.   Based on outcome of plume rise studies conducted during
       first year, perform lidar probes of power plant plumes
       at sites and under met conditions where plume rise and
       spread models were found to perform worst.   Measure
       entrainment constants, energy dissipation rates and
       other parameters needed to refine the model.

   C.   Field test instruments for vertical  wind and temperature
       measurements.  Begin analyses of existing complex terrain
       data looking for influence of surrounding terrain on
       depth of surface inversion and flow speed and  direction
       profiles at night; threshold of  geostropic  flow for
       micro-meso regime breakdown,  etc.

   D.   Begin development of physical and numerical models of
       flow in complex terrain sites to be  studied in  the  field
       next year.

3.2.2   Model Development Progress.

   A.   Formulate impingement kernel  for cases studied to date
       and test against Mohave, Navajo, Four Corners,  etc.,

   B.   Compare refined plume rise-spread  model predictions
       with existing complex terrain data.

   C.   Using results of tasks A and B  above and first  year
       predictability study, estimate modeling error assuming
       perfect meteorological data,  i.e.,  perfect p(M).   The
       outcome will be:

          •  Modeling objectives are achievable if  p(M) can
       be determined with accuracy E.   (This will lead to the
       procedure in Year 2, Model Development, Section D).

          •  Modeling objectives unattainable even if p(M) is
       known precisely.

             1.  Examine cost-effectiveness of alternatives to
       modeling investigated last year,  such as long-term
       tracer study.  If viable method found, abandon  major
       modeling effort.

                  2.  Reformulate air quality standards to achieve
            predictability — resume model development  at Task  D
            of Year 2.
3.3  Year 3
        A.  Continue studies at simulated hill experimental center.
            Examine heat flux effects on flow patterns and boundary
            layer turbulence.

        B.  Final  refinements  of plume rise and spread model,
            culminate in final form of p(P|M).

        C.  Begin full scale study of  micro-mesometeorology at sites
            chosen previous year.

        D.  Begin validation and  refinement operations on physical
            and numerical flow models  using results from field study
            of Step C.

        E.  Begin aircraft studies of free convection  for use  in
            formulating p(C|P,M)  for unstable  conditions.
3.4  Year 4
     3.4.1  Model Development.

        A.  Concluding impingement studies at  simulated  hill  site
            culminating in final form of  p(C|P),M) for stable cases.

        B.  Develop empirical formula for p(M|G) using field data.

        C.  Formulate expression for p(M|G)  from refined physical
            and numerical models.

        D.  Continue developments of p(C|P,M)  expression for  free
            convective case.  Begin numerical model  study  for forced
            convective case.

     3.4.2  Model Development Progress.

        A.  Test these expressions for p(M|G) against  data  from
            Mohave, Navajo, Four Corners, etc.  The  outcome  will

               •  p(M) can be  specified  with  required accuracy E,
            in which case, continued  model  development.

               •  p(M) cannot  be specified  with accuracy E  using
            model only, in which case:

                  1.  Prepare  guideline  for performing necessary
            meteorological measurements  at  any proposed plant site,
            i.e., measurements needed to determine p(M).  Resume
            model development.

                  2.  Investigate alternatives to modeling, such as
            long-term tracer studies  —  if  viable  method,  abandon
            modeling effort.

                  3.  Reformulate standards  — resume model develop-
3.5  Year 5
        A.  Amalgamate all studies into final form of model of second
            highest concentration and  specifications for input data

                             APPENDIX B

     On June 13,  1979,  NAWC forwarded a Workshop package to all the
participants with information pertinent to the tasks  facing  each
panel.  Of particular  concern was the need for the panels to quickly
focus upon the critical issues and to facilitate the flow of infor-
mation between the panels  in order to achieve the goals of the Work-
shop.  The information package included the "strawman" document by
Holzworth and Snyder  (Appendix A); publications by Barr,  et  al. ,
(1977) from the Albuquerque Workshop on Complex Terrain Dispersion,
by Argonne National Laboratory (1977) from the Chicago Specialist
Conference on EPA Modeling Guideline; and by Hanna, et al., (1977)
from the Boston Workshop on Stability Classification and Dispersion

     In addition,  NAWC  prepared material  for distribution to the panel
leaders on June 28, 1979,  which is presented below.  Subsequently,
each panel leader contacted their respective panel members with both
•written and oral  instructions prior to the start of the Workshop in


                          PREPARED BY NAWC


1.1  Model Evaluation  and Application/Model Development and Analysis

     These panels  must generate the basic approach of the Workshop as
a whole during the first session (Tuesday AM).  They must review and
select from  the  basic  scenarios which approach EPA should follow in
their overall program.

     Specifically,  the goals of modeling must be considered and es-
tablished and the relative importance must be given on such topics as:

     •   Centerline plume impaction

     •   Maximum concentration value

     •   Type of models to be considered and their relative merits

     •   Measurement needs

     •   Scale of  experiments -
          Simple controlled (Snyder) versus full-scale power plant

     •   Required  resolution

     •   Priority  of various parameters

     •   Physical  modeling

     •   Plume rise/initial dilution

Furthermore, the Model Evaluation and Application Panel must address
such topics  as peak/mean ground-level impacts and  locations of im-
pacts; i.e., the overall  goal of a model development program relative
to the users.

1.2  Experimental Design  Panel

     Initially this panel  should discuss in general the ramification
of carrying out simple, controlled tracer experiments versus large
scale power plant experiments.   They must address the relative pro-
grams and budgetary requirements and provide interaction with the
Measurement Techniques Panel  on what is required to carry out dif-
ferent programs.

     Once the scale,  resolution, and emphasis of the experiment have
been decided, discuss:

     •   Type of tracer and gas measurements

     •   Ambient measurements

     •   Potential  locations

     •   Logistics  and costs

     •   Surface measurements and instrumentation

     •   Aircraft instrumentation

     •   Tracer samples

     •   Physical modeling techniques

1.3  Measurement Techniques Panel

     Again, this panel will have to start off with general assessments
of measurement requirements for different types of field programs.  Of
particular concern  is the area of turbulence versus meteorological
parameter measurements.   A lack of knowledge of relative rates of
diffusion for different elevations and stability,  as well as different
terrain, has resulted in  difficulties with  model verification.

     Once the experiment  design parameters have evolved,  discuss
methods of data acquisition and recording.  Discuss accuracies and
calibration techniques for meteorological measurements, gas analyzers,
and tracer analyzers. Discuss the applicability of various types of
techniques and potential for using newly developed remote sensing de-
vices for augmenting  experiment usefulness.

     Discuss practicality and  costs.   Interact  with

     •   Data Management - Discuss  data reporting  formats,  data
          control, instrument  accuracies.

1.4  Data Management and Quality  Assurance  Panel

     Before this panel receives clear indications of the basic goals
and concepts which the Modeling Panels  will zero  in on,  this panel
should address such questions  as  how  to utilize the wealth of data
collection in the past by government,  utility industry, and private

     •   Discuss potential methods of  collecting  and utilizing
         data from past tracer and  measurement  programs

     •   Discuss quality assurance  methods  in view  of experiment

     •   Discuss methods of data  management  which allow easy display
         and correction

     •   Consider costs, material requirements


     1)  Discuss best data formats  for  data from  past and future
         experiments with model application and evaluation  panel.

     2)  Discuss reporting methods with measurement techniques
         and experiment design panels.

     Guidance provided by George Holzworth,  the EPA Project Officer
for the Workshop, suggests that both source-oriented (as per example
in Holzworth's "strawman"), and receptor-oriented (as per example in
Snyder's "strawman"), can be accomodated in the long-term EPA research
plans.  However, specific experiment design,  scheduling, priority of
research, and interaction with other  programs  (i.e., EPRI, DOE, and
NOAA) are major considerations for  the  Workshop.

     The present Workshop plan calls for alternate panel and plenary
sessions arranged so that after an initial plenary session on Monday,
there are at least three separate feedback  loops between individual


and assembled panels on the succeeding days: Tuesday through Thursday.
Separate panel  leaders meetings are part of the  loops,  with their
closing session on  Friday.   Figure B-l diagrams the  information
flow in each  loop.   Arrows  pointing both ways . indicate flow  be-
tween panels  at plenary  sessions.  The single direction arrows,
on the other hand,  are meant to emphasize the natural flow  of develop-
ing ideas from  panel to  panel.   The MD&A Panel heads the column be-
cause it has  to be  the original source of a well-defined quanti-
tative demand on the other  panels for development  and critiquing
of the MD&A panel's particular idea.  It seems natural for  MD&A to ask
ED how they would  test the  idea in an experiment;  then  ED asks MT
about possible  measurements techniques, and MT passes the  idea in its
current stage of development to DM & QA to acquire their input on how
the data can  be managed.  Finally, ME&A plays some conceptual simula-
tions to see  whether the particular idea, at  this  stage, will fly,
and if so, whether  it meets their set of applicability criteria.  In
succeeding loops the particular idea is either refined or discarded.
Finally, on Friday,  the  panel leaders polish a draft report covering
the surviving ideas and  fit them together as  a  consistent  set of
program recommendations.

     Probably not all ideas finally developed will appear in  the first
loop, but may be appended as inspiration produces them along the way.
The inspiration for a new idea may come from any panel and  should be
inserted into the  pipeline  at the first available  plenary session.
At the initial plenary session on Monday many ideas will be formulated
and these will serve as the initial "seedbed".   Some ideas  not meeting
wholehearted  support at  this session could  still  be subject to
processing at least once through the loop to make sure everyone has
a chance to think  the matter through.

     A more specific example of how the Panels  will interrelate is
shown in Figure B-2, which  is a flow chart showing how some specific
recommendations would evolve.  This would begin with listing of the
general objectives and parameters to be measured by the Model Develop-
ment and Model  Applications Panels.  Their ideas would be  passed on
to Experimental Design,  who would devise an instrumentation array
design and recommend sampling modes (time of day,  time of  year, dura-
tion, etc.).   Their list would go to the Measurement and Data Manage-
ment Panels,  who would  recommend specific instruments and  list data
handling/QA-QC, respectively.  Those recommendations  would  go back
to the other  panels again,  and each would refine the original design
and develop a summary of recommendations.

     A suggested schedule for the week is shown in Figure  B-3.  The
specific recommendations,  as shown in the flow chart,  are  connected





(DM & QA)

(ME & A)
•^ /
s ^
/• s
*v f
s- -s
X '
/ •>)
>s ^
x V
Figure B-l.  Flow diagram for Workshop,

         & ANALYSIS
               MODEL EVALUATION
                 & APPLICATION
                   1.  GENERAL  OBJECTIVES
                   2.  PARAMETERS TO BE MEASURED
                                TUES. A.M.
                   1.  INSTRUMENTATION ARRAY
                                 WED.  A.M.
WEb.  EVE.
               DATA MANAGEMENT
3.   QA/QC
                        TO OTHER PANELS
Figure B-2.   Flow  diagram for  specific complex terrain model study
recommendat ions.

#1 #2 #3 #4 #5








G E r



1 E R A L C C
V1 P I
\ ^


' S E S S I [

. E N A R Y^

) N S
^ T I 0 N S







FOR #1



FOR #2.
>^ ~y

FOR #3

FOR #4


FOR #5
Figure B-3.  Suggested schedule for Workshop as detailed by Panel Leaders in
their letters to Panel Members.

with clashed lines.  In addition, each  panel  should have a list of
selected discussion topics for  the  periods  noted on the schedule.
The Panel Leader should  select  the day's topic(s).  Also, each panel
will address the anticipated costs  for the  program recommended by
that panel and determine the percentage of total  program funds which
should be allocated to each aspect of the study  (e.g., Model Develop-
ment 25%, Experimental Design 15%,  etc.).   Each Panel Leader would
be responsible for summarizing  the  consensus of recommendations of
his panel and interfacing with  other Panel Leaders.   Continuing
dialogue between the  leaders will allow the panels to continually
update and refine their  design  recommendations.

     Already a variety of ideas have been proposed and  appear in
various memos and letters that have been distributed to Panel Leaders
and participants.  These  ideas represent responses to questions about:

     1)  Deformation  of  streamlines and parallel deformation of
         the concentration pattern  in  passing  over complex terrain,
         under different stability  regimes.

     2)  Changes in dispersion  over complex terrain from that for
         flat-land stability types.

     3)  Changes in entrainment and plume rise factors over complex

     4)  The nature of slope flows  in  complex  terrain, and the  role
         of radiation in producing  them.

     5)  The nature of flow separation and its effect upon dispersion.

     6)  The validity of using  stagnation point concentration in
         the case of  direct  impaction  of  a plume on a  cliff  (and
         how thit type of flow  can come about in nature,  if at

     7)  The problem  of  transport and dispersion of  stagnation

     The preparation  of  a final smooth report  on this Workshop  will
be greatly facilitated if there is an  orderly recording of ideas and
their development, including reasons for their discard, if that is the
action taken.  It would  also be useful to name the persons in the
notes responsible for initial introduction of  an idea  and those
responsible for various  seminal amplification of an idea.  It is not

necessary to record al 1  the nuances  of a. debate,  but  careful record-
ing of technical details  (especially with instrumentation) would be
helpful.  It is easy  to  assume  that  everyone is familiar with code
names and jargon.  The principle on  which an instrument works should
be given along with its  standard specifications.

     It is most critical to the successful conclusion  of the Workshop
that there are adequate  opportunities throughout the Workshop  for
interchange of information  between the panels.

     Since the Experimental Design,  Measurement  Techniques, and the
Data Management Panels are  very  much dependent on the  specific
directions to be generated  by the Modeling Panels, these directions
must be conveyeu  early, no later than  at the Tuesday  Evening Executive
Panel Leader Session.

                            APPENDIX  C


     During a two-week period  immediately following the Workshop,
the panel members had an opportunity  to review and comment on the
written Panel Recommendations  to  EPA.   Appendix C contains specific
comments, received by Panel Leaders and the Project Director, which
are presented for the purpose  of  amplifying the viewpoints by panel
members which they believed required  further clarification.

                               3  August 1979
Mr. Maynard E. Smith
Meteorological Evaluation  Services,  Inc.
134 Broadway
Amityville, New York   11701

Dear Maynard:

     As we agreed  in  our telephone  conversation concerning the
report of our panel,  I am  writing  you about a potential problem that
was not discussed  by  the panel.   This  potential problem is the
generation of turbulent wakes in the vicinity of the terrain interface
during the field  experiments by the  hardware (masts, sampling devices,
support equipment) and by  certain  activities  within or  near the
sampling arrays that  would significantly enhance  turbulent mixing or
otherwise alter the boundary  layer characteristics during the stable
regime.  These wake effects are most likely to be significant for
the small scale experiment but  may be  significant for the intermediate
and large scale experiments as well,  depending on  the relative height
and density of the natural roughness  elements that are presented.  It
is clear that the  potential  wake effects  or flow disturbances
attributable to the measurement techniques, hardware and support
activities should  be  carefully evaluated as part  of the experimental
design process and that these effects may limit  the scale of the

                               Harrison E.  Cramer




                        William  H.  Snyder
     As originator of the small  hill  study concept,  I take  this
liberty to defend the plan.   I feel that  many aspects of the plan
have been misunderstood, indeed,  misconstrued, perhaps only because
all have not had the opportunity to  perceive the plan as first
proposed.  Numerous questions were  raised at  the Workshop; I will
attempt below to answer  the most frequent and serious ones.

     1.  Cost of Meteorological  Towers:   I have  been assured by Mr.
Michael Fleissner of Rohn Mfg. Co., Peoria,  111., that the erected
cost of a 152 m (500 ft) meteorological  tower,  complete with  guys,
lights and ladder, would range between $32,000  and $35,000.  An
upper estimate of the cost of installing  anemometers is 6 man-weeks
or $6000 (this estimate  does  not include the cost of the anemometers
themselves).  It is evident that substantial savings would be  achieved
by constructing 5 towers at essentially  the same site and  the same
time.  Hence, the cost of 5 meteorological towers is well within the
constraints of the budget (~  5%).

     2.  Scaling to a Large  Hill:  The primary  goal of the small hill
study was to understand  the physical  mechanisms involved in the
impingement and/or diffusion  of  plumes to a hill surface.   It was
definitely not conceived as a study whose results would be applied
ipso facto to the larger hill or "real"  terrain.  (From that  point
of view, however, it is  interesting to note that often the results
of fluid modeling studies conducted at scale ratios of 300:1, 1000:1,
even 10,000:1, are  applied  to  full  scale situations, whereas,
scaling the small hill results by factors of 2:1,  5:1, at most  10:1,
appeared to be an insurmountable obstacle!).  The point  is  that
once we understand the physical  mechanism involved in plume  impinge-
ment/diffusion onto a sloping, three-dimensional surface,  we will
then have a much more clear idea of how  to construct a mathematical
model to handle the problem.

     An example may help to clarify the  point.   Laboratory  studies,
guided by fundamental principles, have shown  that,  under strongly
stable conditions, fluid is  constrained to move in horizontal planes.
A plume with an elevation lower than a nearby hill, therefore, cannot
go over the top, but must, irstead, travel around the sides. If the
wind vector at the source is  aimed  precisely  at  the centerline of


the hill, laboratory studies have shown that resulting surface con-
centrations will be essentially equal to what they would have been
at the centerline of the plume in the absence  of the hill.   The
laboratory studies have also shown,  however, that surface concentra-
tions are drastically reduced  if  the wind  direction is  changed
only slightly.  What is obviously lacking in the laboratory studies
is the natural wind meander, which can only be  obtained from field
experiments.  Once the physical  mechanism,  i.e., wind  or plume
meander factor, is understood, it will be a relatively simple matter
to extend the concept to larger hills, where the standard deviation
of wind direction fluctuations has been measured.  The small  hill
study was conceived as a project wherein detailed and extensive
measurements con Id be made on a manageable scale.  The size of the
hill (100 m) was chosen to be large enough to frequently  be much
higher than the very thin  (sometimes absent)  jLurjcml^nt^ surface
layer under very stable atmospheric conditions, yet small enough
to eliminate the horrendous  logistics problems of large scale

     Plume meander is obviously  not the only  missing factor in
laboratory or mathematical models.   We also need to know the effects
of anabatic and katabatic winds; how closely the  plume centerline
approaches the hill  top as the  stability  is  reduced from very
stable through neutral; how frequently does  "strong" stability
occur and how is wind meander related to stability; how  are the
rules changed as the wind profile  shape or  the  density  profile
shape vary, etc.  If these kinds of questions can be answered from
a small hill study—and I believe they can from a properly conducted
one—we will have progressed a long way  towards our goal of construct-
ing a model suitable for use in complex terrain.

     3.  Real-Time Data Collection:  At least  two panels at the
Workshop indicated that time averages, not to exceed 10 minutes in
length, were essential to understand that some real-time data would
be very useful,  but dismissed the idea of total real-time data collec-
tion because of a perceived excessive expense.  I contend that a
real-time feedback system can be established that will be relatively
simple, reliable, and of quite reasonable cost—even more economical
than any other system when all factors are considered over the total
duration of the small-hill study.  There are three questions to be
answered here:  (1) What tracer/sampling  system could  be used?
(2) What time resolution is necessary?  (3) How much would a real-
time feedback and recording system cost?

         (a)  Tracer/Sampling  System:  I  propose to use ethane
     (COHC) as the tracer and flame ionization  detectors  (FID's)
       ^ O


for concentration measurements.   Ethane is neutrally buoyant,
sufficiently inert chemically and readily available at reasonable
cost.  FID's (total hydrocarbon analyzers)  are we 11-understood,
reliable, readily available,  fast response (~ 1 sec), linear
in the range of 0.5 to  10,000 ppm (i.e., can measure dilutions
on the order of 2x10 ),  and are not terribly expensive (~ $2500/
unit).  They produce an analog output voltage that is readily
digitized.  Adequate surface  concentrations (i.e., above  back-
ground) may be obtained with  reasonable release rates of ethane
(calculations are easily  made).   It appears quite feasible  to
rig a tubing network such that samples from 10 locations on the
hill surface are continuously pumped past  each of  10 FID's.
Through a switching network,  then, the FIDs are able to repeti-
tively sample each of the  100  locations on a once-per-ten-second
basis—conceivably much faster than that—as laboratory studies
have rather easily obtained  frequency responses of 300 hertz.

     (b)  Time Resolution  Required:   To fully understand the
physical mechanisms, resolution of concentration fluctuations
as well as wind speeds  on time scales  much  shorter than  10
minutes is  essential.   The necessity for time resolution of the
wind fluctuations is obvious.  The necessity for  resolution
of concentrations is not  so  obvious, but  laboratory studies
and some large scale field studies have shown that semi-coherent
vortex shedding may occur in the lee of hills under  strongly
stratified conditions.  This vortex shedding in the lee causes
an oscillation of the plume on  the upwind side of the hill,  which
can markedly reduce surface concentrations.  The vortex shedding
period is expected to be  on  the order of a  few minutes, so that
this physical mechanism would  be completely obscured by observing
only 10 minute averages.  Similarly, any other physical mecha-
nisms taking place on time scales smaller than 10 minutes would
be obliterated by 10 minute  averages.

     (c)  Data Feedback  and Recording:  The above  discussion
points towards 10 second  averages at each  of 100 locations for
a presumed study period of 3 hours,  leading to  a total  of
100,000 samples/day.  This  sampling rate and number of samples
obviously points to a  mini-computer  recording on magnetic
tape.  A system to handle this job would  cost under $100K.
It can easily be set up to automatically and periodically
sample each analyzer, to  record each sample on magnetic tape,
and  to display real-time and/or running-average information
at all sampling locations simultaneously.   At the end of each
study period, all information is immediately available for
comparing with models and for user distribution.  This system


     is to be compared with something equivalent to syringe sampling,
     where a new syringe  is  filled every 10 minutes at each of  100
     locations for a period  of  3  hours,  yielding 1800 samples that
     must be individually  labeled,  handled, analyzed,  recorded,
     flushed, etc., each  day.   The choice is obvious.  A comparable
     system for wind measurement  and recording  is likewise in order.

     4.  Source Configuration and Management:  If the vertical width
of the plume is too large  compared to  the hill height, we will be
unable to learn much about the  flow structure over the hill,  because
surface concentrations would be  essentially uniform.  If its vertical
width is too small, it will  not be possible to resolve  the plume
structure as it approaches or encounters the hill, e.g.,  lidar
measurements would be unable to resolve  the plume  as it approaches
the hill, and similarly,  too many samplers would be required on  the
hill surface.  An  appropriate  number appears to be a   = 10 to
15 m for a 100 m hill.  Such plume  widths could be obtained oy placing
the source an appropriate  distance upwind for the existing stability
class.  From Turner's workbook, indicated distances are  1  km for
F-stability and 400 m for  D-stability  (this is another reason for
having a mobile source).   An alternative would be  to configure  the
source to obtain the desired initial plume widths,  for example, by
emitting the tracer through an array of tubes spaced in a rectangular
matrix in the y-z plane.

     Several Workshop participants expressed the opinion that once
the source was fixed and  sampling began,  the source should  not be
moved again for the duration of the  study period,  i.e. ,  3  hours.
I agree with this concept  in principle,  but, in practice,  it may
be entirely appropriate to move the  source.   Suppose,  for example,
after collecting samples  for a  one-hour  period, there is an obvious
and permanent shift in the wind  direction of 180°.  This could be  the
case (and possibly, quite  predictably) shortly after sunrise if  the
100 m hill were located in a broad sloping valley.   It seems to me
fruitless and wasteful of  resources to continue the scenario another
two hours; it would be far better to move the  source 180°  around
the hill and begin a new  scenario,  obtaining useful data.  It would
be obvious from the wind  records,  in any event, that the three-hour-
average concentration for  the first  scenario  would be  one-third
the one-hour-average concentration.  Of  course, strict  protocols
would be mandatory and decisions  would have to be  based  on prior
experience, but a rigid specification  of an absolutely fixed source
position is too restrictive.

     5.  Anabatic and Katabatic Winds.  The lack  of knowledge concern-
ing the nature, strength,  and thickness  of anabatic and katabatic


winds was apparent at  the Workshop,  but the general consensus appeared
to be that they would be  small to insignificant on the  100 m hill,
yet predominant  on a  500 m hill.    Because  there  are numerous
physical mechanisms to be understood before constructing  an adequate
mathematical model  (the nature of the impingement process, the close-
ness of approach  of streamlines to the hill surface,  the wind meander
factor, anabatic  and  katabatic winds, etc.), it is  logical  to
eliminate as many variables as possible in order to fully understand
the remaining processes.   If anabatic and katabatic winds are insig-
nificant on the 100 m hill, it is therefore a  logical first  step.
In any event, a few smoke studies before any equipment  is set  up
would provide very useful knowledge on the existence and nature of
any such thermally generated surface winds, so that we may  be prepared
to quantify them  as necessary.

                               August  9,  1979
Dr. Bruce A. Egan
Environmental Research  & Technology,  Inc.
3 Milata Drive
Lexington, Massachusetts   02173

Subject:  Your memorandum  AQC-833  of  July  25,  1979,  concerning EPA
          Rough Terrain Workshop

Dear Bruce:

     I was away from the office until your deadline for comments so
I am sending a copy of  this  letter to Einar Hovind.

     I find no fault with  the  panel  report.  It appears to reflect
most of the concerns that  were expressed at the  panel sessions.

     Upon reflection and a plotting to scale I  am  concerned that 100
tracer samplers will not be enough  to  define the ground level concen-
tration pattern and concentration  gradient normal to the hill.  For
examp1e, an oval hill that peaks at  120  meters with a six to one
slop,, .vould require 25  samplers at 20 meter spacing along the 50
meter contour level for just one quadrant.  The  recommendation should
be 200 samplers.

Dr. Bruce A. Egan              page 2               August 9, 1979
     The Workshop was enjoyable and I  look forward to seeing  the

                              Very truly yours,

                              TRC - THE RESEARCH CORPORATION
                                     of New England
                              Norman E.  Bowne,
                              Vice President & Chief  Scientist
cc:  Einar L. Hovind
     North American Weather Consultants

                               August  13,  1979
 Mr.  Einar L.  Hovind
 Vice President,  Air Quality
 North American Weather Consultants
 600  Norman Firestone Road
 Goleta,  California  93017

 Dear Einar:

      I am enclosing a copy of my  letter of August 1  to Maynard.  Note
 the  circled third paragraph*.   If  such a distance range is not already
 covered under the group that  waas working on project design, I think
 it is important  to show how  difficult  it will be to have the tracer
 "hit the hill" as the release point  is moved from  two km to four km
 up wind.

      For your general information Gerard DeMarrais telephoned Montana
 Power last week  to inquire as to the availability  of the small hill
 upon which the meteorological tower is  located for field experimental
 work.   Unfortunately that hill is not  100 meters high and it is more
 conical in shape than the 3 to 1 aspect  ratio recommended by the Work-
 ing  group of  which Maynard Smith was the head.
*"Perhaps an item 8 under the  Small  Scale effort should indicate  a
 distance range up-wind from the  hill  be recommended for tracer re-
 lease.  I personally would  like to  see some data collected at  both
 2  and  5 km up-wind from the first  possible impingement point on the
 hill.   Such an investigation will clearly illustrate  the less precise
 air  flow pattern for a greater distance.  Perhaps it could be better
 stated as not less than 2  km  up-wind  with a second release  effort
 not  more than 6 km up-wind."

Mr. Einar L. Hovind               page  2              August 13, 1979
     I appreciate  the  opportunity to join with others at  the Workshop
in North Carolina.   However,  I remain unconvinced that  the findings
of a detailed  study  project using a hill in the  center of a valley
will answer  the  real life problems of the imagined impingement on the
shoulder terrain many  kilometerss away from a power plant in  the
center of the  valley.

                               Sincerely yours,
                               Loren W. Crow, CCSJ

                                   TECHNICAL REPORT DATA
                           (Please read Instructions on the reverse before completing
                                                          3. RECIPIENT'S ACCESSION-NO.
   November  1979

  E.  L.  Hovind, M. W. Edelstein, and  V.  C.  Sutherland
  North American Weather Consultants
  600 Norman  Firestone Road
  Goleta,  California 93017
                                                           10. PROGRAM ELEMENT NO.
                1AA603   AB-050  (FY-79)
              11 . CONTRACT/GRANT NO.

  Environmental  Sciences Research Laboratory - RTP, NC
  Office of Research and Development
  U.S.  Environmental Protection Agency
  Research Triangle Park, North Carolina  27711
                                                           13. TYPE OF REPORT AND PERIOD COVERED
                Final   3/79  -  10/79
              14. SPONSORING AGENCY CODE
16. ABSTRACT           •

       During the period of July  16-20,  1979,  an EPA-sponsored Workshop  was  conducted
  in  Raleigh, North Carolina,  to  address  problems associated with  plume  dispersion
  modeling in complex terrain.  This  Workshop  was intended to aid  in  the design of
  a proposed EPA-funded research  program  dealing with this topic.  Workshop  participants]
  represented a cross-section  of  environmental  organizations, control  agencies,
  industry and the scientific  community with technical background  and expertise in
  complex terrain modeling and field  studies.

       The Workshop was organized into  five panels:  Model Development and Analysis;
  Model  Evaluation and Application; Experimental Design; Measurement  Techniques; Data
  Management and Quality Assurance.   This report contains the unabridged recommenda-
  tions by each panel as summarized by  the Panel Leaders.  Also  included are presenta-
  tions by invited speakers who presented summaries of related complex terrain dis-
  persion programs currently being sponsored by industry and by  government agencies
  other than the EPA.
                               KEY WORDS AND DOCUMENT ANALYSIS
  Air pollution
 ^Atmospheric diffusion
 ^Mathematical models
                                             b.IDENTIFIERS/OPEN ENDED TERMS
                           c. COSATl Field/Group
                      RELEASE TO PUBLIC
                                             19. SECURITY CLASS (This Report)
                           21. NO. OF PAGES
                                             20. SECURITY CLASS (This page)

                                                                        22. PRICE
EPA Form 2220-1 (9-73)