United States
Environmental Protection
Agency
Atmospheric Sciences
Research Laboratory
Research Triangle Park, NC 27711
Research and Development
EPA/600/S8-86/011   M ay 1986
Project  Summary
MPDA-1:  A  Meteorological
Processor  for
Diffusion   Analysis  —
User's  Guide
James Paumier, David Stinson, Terry Kelly,
Catherine Bellinger, and John  S. Irwin
  Version 1 of the Meteorological Pro-
cessor for Diffusion Analysis (MPDA-1) is
a first attempt to provide a processor that
can organize available meteorological data
into  a format  accessible  to diffusion
analysis. MPDA-1  provides  methods for
preparing three types of data: National
Weather  Service (NWS)  twice-daily
radiosonde reports, NWS hourly surface
observations, and user-supplied on-site
data. To incorporate the surface scaling
parameters, the meteorological processor
is structured in accordance with current
concepts of the idealized states of the
planetary boundary layer. Profiles of wind
velocity, temperature, and the standard
deviations  of vertical and  lateral  wind
velocity fluctuations  at user-specified
heights are estimated.

  This Project Summary was developed
by EPA's Atmospheric Sciences Research
Laboratory, Research Triangle Park, NC, to
announce key findings of the research
project that is fully documented in a
separate report of the same title (see
Project Report ordering information at
back).

Introduction
  The  availability of  many  diffusion
models, combined with the availability of
new data sources, has created a need for
a processor that can  organize  the
meteorological data into a format accessi-
ble to diffusion analyses. Version 1 of the
Meteorological Processor for  Diffusion
Analysis (MPDA-1) is an attempt to fill this
need.
  Research has been conducted to obtain
a better characterization of the diffusion
of air pollutants and a better understand-
ing of the meteorological variables of most
concern to diffusion analyses. Most of the
early popular attempts to estimate diffu-
sion of air pollutants were based on the
Gaussian-plume model.  It was recognized
that the only relevant measurements of
wind fluctuations likely to be available for
routine studies were those contained in
conventional traces  of horizontal wind
direction. Simple rules were developed for
obtaining  the  lateral spread,  based on
wind-direction trace data. In the absence
of such data, the effects of thermal
stratification in the lower atmosphere were
represented in broad categories of stabili-
ty, defined in terms of meteorological data
routinely  available  in  surface weather
observations.
  By the early  1970's, air quality simula-
tion models were viewed  as tools  to
estimate the relative magnitudes of pollu-
tant  concentration  distributions from
various sources, thus providing a rational
basis for strategies of air quality improve-
ment or maintenance.  Most of the air
quality  simulation models developed in
response to these modeling requirements
were based on the general  Gaussian-
plume model.  Gaussian-plume diffusion
was estimated for each hour with hourly
values of surface wind  speed  and direc-
tion, ambient air temperature, the Pasquill
stability category, and mixing height.
Typically, the wind direction was assumed
to be constant with height. Some models
provided  for  the  variation  of  wind

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speed with height with a power-law ap-
proximation; the power-law exponent was
specified as a function of Pasquill stabili-
ty category. When temperature gradients
were needed,  as for the estimation of
plume  rise during stable stratification,
values  were assumed for each Pasquill
category. It was further assumed that the
diffusive characteristics of the atmosphere
were  vertically   and   horizontally
homogeneous within the mixing layer.
  Practical methods for characterizing the
profiles of  wind, temperature, and tur-
bulence within the  planetary boundary
layer are now beginning to be developed.
These methods are improving as new data
are acquired  and analyzed. In the next
decade,  measurement  methods  may
develop to the point that frequent routine
measurements of the  structure of the
planetary boundary  layer may be made
remotely by using Doppler-acoustic radars.
  When these new methods of data ac-
quisition  are  perfected,  it may become
possible to specify routinely the following
meteorological data: mixing height,  at-
mospheric  stability, the profiles of the
standard deviations of vertical and lateral
wind velocity fluctuations, and the profiles
of  wind  velocity  and temperature.
Availability of these data on an hourly
basis has important implications for diffu-
sion modeling.  Standard  deviations of
wind-speed fluctuations could be used to
characterize the sigmas in a Gaussian-
plume model. These data would allow use
of improved  algorithms  for  estimating
plume rise and for estimating wind direc-
tion shear effects, which have largely been
ignored in routine modeling studies of dif-
fusion. Also,  these  data would accom-
modate Monte-Carlo particle trajectory
models of diffusion or grid models that use
eddy diffusivities.

Discussion and Results
  The MPDA-1 consists of a preprocessor
and  a  meteorological  processor  (met-
processor), the output from which can
then be used by a diffusion model. The
preprocessor can accommodate data col-
lected by standard radiosondes, surface
observations, and multilevel observations
at special meteorological sites (on-site
observations).  The preprocessor prepares
and combines the data from these three
sources into one unformatted file for use
by the metprocessor. The metprocessor
estimates the surface scaling parameters
and the profile variables. A selection of
methods is available for determining most
meteorological parameters; these options
reflect differences in the theoretical deriva-
tions of the algorithms.
                                    2
Preprocessor
  The preprocessor consists of a series of
programs that format meteorological data
according to required specifications. The
preprocessor can accommodate data from
three sources:
  National Weather Service (NWS)
   radiosondes,
  NWS surface weather observations,
   and
  User-provided, on-site observations

  The programs in the preprocessor were
developed specifically for standard NWS
radiosonde and surface observation data.
The data are available from the National
Climatic Data Center (NCDC) in Asheville,
North Carolina.  The  preprocessor uses
radiosonde data in NCDC's TDF56OO for-
mat, and the surface observations are in
the TDF1440 format.
  The  type  of  meteorological data
available will dictate which programs in
the preprocessor will be used. For exam-
ple, if no radiosonde data are available, all
of the radiosonde preprocessor routines
can be skipped, but an empty file must be
created for use by succeeding programs.
If the user's data have  already been ex-
tracted  and quality-assessed,  only the
CONVERT  programs may be needed,
because they prepare the data in the for-
mat required by MERGE. The programs in
the preprocessor are  described   briefly
below.

  SCAN  These programs scan the tapes
  containing raw input data and produce
  a list of stations and dates recorded  on
  the tape. The output report is not used
  as input to any other  programs.

  EXTRACT  These  programs  extract
  data for the desired time period from the
  raw input data tapes. The user provides
  the range of dates of  interest by speci-
  fying Julian beginning  and ending dates,
  the station identification code,  and  its
  latitude and longitude.  The specified raw
  data are extracted from the tapes and
  produced as output files.

  CONVERT  These  programs perform
  two functions. 1. They reformat the out-
  put files to  comply  with the  format
  specifications of the  MERGE program.
  All programs after CONVERT use the
  same format. 2. They convert variables
  to the set of units  required  by the
  metprocessor.

  QA  QA programs are available for all
  three  data types. Execution of these
  programs is optional.  The output files
  created  by the  CONVERT programs
  meet the format requirements of the QA
  programs as well as those for MERGE.
  The QA programs for radiosonde and
  surface observation data scan the data
  sets for values that  do not satisfy the
  criteria specified by the  user. The QA
  program for on-site data gives the usei
  a choice between specifying acceptable
  ranges for all variables measured or us
  ing default  values. All  programs
  generate reports of values that do no'
  satisfy the assessment criteria.
  REDUCE  Because radiosondes extent
  to  heights  considerably  greater thai
  those  required  by most  diffusioi
  models, the reduction program delete
  data above a user-specified height ii
  each report. This routine also has a usei
  specified option to adjust all the height
  of the sounding from mean sea level t
  above ground level  (AGL). The mei
  processor  requires  heights to  b
  specified as AGL.

  HRLY-INTERP  If the time interval be
  tween soundings is  greater than on
  hour, this interpolation program must b
  used to prepare the data in the hourl
  format required by  MERGE. The us<
  specifies the range of dates over whic
  interpolation is  required,  and the pr<
  gram linearly interpolates the data ov<
  time. The output file generated contair
  hourly radiosonde data for the specifit
  date range.

  MERGE   MERGE combines the thn
  output  files  of the preprocess
  (radiosonde, surface observation, ai
  on-site data)  into  one  unformatt
  (binary) file for use by the metprocess*
  The result is a sequence of unformatt
  day-records. A day-record consists
  one 24-h day of output, with 24 hou
  observations of radiosonde, surface, a
  on-site data.

  Before executing MERGE, the three d<
files  must  be  in  hourly  intervals a
ordered sequentially by local standard tii
(LST). The preprocessor can prepare £
or all of the files for MERGE. However, 1
preprocessor does not have to be used
prepare the data, as long as the forn
specifications for MERGE are met. In
dition to the unformatted output file u,<
by the metprocessor,  MERGE will a
generate a formatted output file if the u
requests it.

Metprocessor
  The metprocessor uses data combii
by MERGE to calculate the meteorolog

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parameters required by diffusion models.
Estimates of the  fundamental surface
scaling  parameters  (including surface
fluxes and Monin-Obukhov length), sur-
face roughness length, and mixing height
are determined first. This is followed by
estimates of wind  velocity, temperature,
and standard deviations of the horizontal
and  vertical wind  speed fluctuations at
heights specified by the user. Methods are
available that require only NWS radiosonde
and surface observation data to estimate
all  the  variables.  Other  methods are
available that incorporate on-site data to
estimate variables.
  The metprocessor consists of a  main
program and a series of subroutines that
calculate the individual parameters and
construct profiles.
  The user's choices for  a method of
calculation for each of the parameters and
profiles are listed in Table 1. Each method
is encoded as a separate subroutine.
  The metprocessor processes one day-
record (24-h record) from  MERGE at a
time.  All data are in local standard  time.
Because processing is day-by-day, infor-
mation   from  the  previous  day is
unavailable for  computation during the
current day. This limitation must be con-
sidered  if the  user adds additional
subroutines.


Conclusions and
Recommendations
  MPDA-1 offers  a set of methods for
preparing three types of data for use in dif-
fusion  analysis:  NWS   twice-daily
radiosonde reports, NWS hourly surface
weather observations, and user-supplied
on-site data. A selection of methods  is
available for estimating vertical profiles of
wind velocity and temperature and the
standard deviations of vertical and lateral
wind velocity fluctuations. Procedures are
also provided for estimating mixing height
and surface scaling parameters, including
the Monin-Obukhov length.
  The main feature of MPDA-1 is its flexi-
ble design, which will allow easy adapta-
tion to new processing methods and new
diffusion models. This is true also for the
preprocessor portion of the system. Each
method for calculating a parameter or pro-
file is a separate subroutine; the modular
design adapts easily to changes in  input
data formats. The modular design is also
used  in the preprocessor.
  Because each method computes only
one surface parameter or constructs a pro-
file, the user can easily add an alternative
method for a parameter and use it in the
computations, rather than one supplied
with the system. The user is encouraged
to submit any subroutines or algorithms
that demonstrate improved accuracy or
speed. The part of the preprocessor con-
cerned with on-site data contains several
variables that are not used in the MPDA-1.
These variables are thus available to the
user who develops his own metprocessor
algorithms. The MPDA is a continually
evolving system; user comments and sug-
gestions are welcome.
  MPDA-1  was developed with specific
design criteria in mind. These criteria and
the methods by which they were met are
listed in Table 2. The criteria reflect the
goal of creating a system with as much
built-in flexibility as possible.
  At least one method for each parameter
is provided, so that  the system  can be
used even if only NWS upper air data and
surface observations are available. The up-
per air data used during development of
MPDA-1 were from NWS radiosondes col-
lected at  0000 Greenwich Mean Time
(GMT) and  1200  GMT.  Because  the
MPDA-1  metprocessor  requires  hourly
data, the  soundings are  interpolated to
hourly values. Adding on-site data from
multilevel  instrumented towers or remote
sensors would expand the number of
usable methods available and improve the
results for  the  lower  part of  the
atmosphere.
  As with any system, the MPDA-1 does
have limitations. The system is easy to im-
plement, but the user should note that cer-
tain methods require more sophisticated
input data than are typically available in a
routine weather observation.  The user
should specify methods that are compat-
ible with the data available. For example,
if on-site data are not available, then some
of the methods cannot be fully utilized.
  With these limitations in mind, the user
will find the MPDA-1  to be a flexible and
effective system for organizing meteoro-
logical data into a format accessible to
diffusion analyses.

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Table 1.    Choices of Subroutines Containing Methods of Calculation
          Parameter or Profile                    Subroutine Name
              for Parameters and Profiles in the Metpmcessor
                                              Description
Surface roughness length, zo (m)
Surface heat flux, H0 fW/m2)
  and
Surface friction velocity, u* (m/s)
Monin-Obukhov length (m)

Convectivefy driven mixing height (m)
Mechanically driven mixing height (m/
Heights (m)
Temperature profile f°C)
Wind velocity profile Im/s)
Vertical and horizontal wind velocity
fluctuations (variances) (m/s)
ZOMOD1
ZOMOD2

 HMOD1
   and
USMOD1

 HMOD3
   and
USMOD3

 HMOD4
   and
USMOD4

 LMOD2

ZCMOD1
ZCMOD2


ZCMOD3


ZMMOD1

ZMMOD2


ZMMOD3


HTMOO1

HTMOD2

 TMOD1



UVMOD2


UVMOD3


UVMOD4
SWMOD1
   and
SVMOD1

SWMOD2
   and
SVMOD2
Roughness length estimated from user-defined land-use and
terrain types.

User-specified value, or if unavailable, a default value of 0.3 m.

Heat flux estimated using surface layer similarity theory and
low-level profile data of wind speed and temperature difference.
                                                                        Parameterization of surface energy fluxes in terms of standard
                                                                        weather observations of cloud cover, temperature, and near-
                                                                        surface wind speed and surface roughness length 
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Table 2.    Design Criteria for the Metprocessor
                  Need                                   Implementation

— New methods must be easily added:          — The computations associated with each
  obsolete methods must be  easily deleted.        method occur within individual
                                                subroutines: to add or delete a method,
                                                only a change in the main program is
                                                needed.

— The input data and results from              — The data are accessible to all subroutines
  computations must be readily accessible.         in their entirety via COMMON blocks.

— The code must be standard for most         — ANSI FORTRAN 77 was used to code the
  computer systems.                             system.

— Must be able to  vary output by              — Output is generated by subroutines: thus,
  parameters and style,  depending on the          new output styles or variable lists can be
  requirements of  the diffusion model.             easily added by adding subroutines.
                                                                                   •&U. S. GOVERNMENT PRINTING OFFICE:  1986/646-116/20837

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       James Paumier, David Stinson,  Terry Kelly, and Catherine Bellinger are with
         Computer Sciences Corporation, Research Triangle Park, NC 27709; the EPA
         author John S. Irwin is with the Atmospheric Sciences Research Laboratory,
         Research Triangle Park, NC 27711.
       D. Bruce Turner is the EPA Project Officer (see below).
       The complete report, entitled "MPDA -1:A Meteorological Processor for Diffusion
         A nalysis—User's Guide," (Order No. PB 86-171402/A S; Cost: $ 16.95, subject
         to change} will be available only from:
               National Technical Information Service
               5285 Port Royal Road
               Springfield, VA 22161
               Telephone: 703-487-4650
       The EPA Project Officer can be contacted at:
               Atmospheric Sciences Research Laboratory
               U.S. Environmental Protection Agency
               Research Triangle Park, NC 27711
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
EPA/60O/S8-86/O11
             0000329    PS

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