United States
Environmental Protection
Agency
Atmospheric Sciences
Research Laboratory
Research Triangle Park, NC 27711
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Research and Development
EPA/600/S3-86/017 June 1986
Project Summary
Description of the Savannah
River Laboratory
Meteorological Data Base for
1975 to 1979
John S. Irwin, Thomas M. Asbury, and William B. Petersen
A summary is presented of a mete-
orological data set collected during the
period 1975 to 1979 by the Meteorology
Group of the Savannah River Laboratory
at the WJBF tower located 11 km
southeast of Augusta, GA, and 23 km
southwest of Aiken, SC. These data con-
tain 15-min averages and standard devia-
tions of temperature, horizontal wind
speed and wind direction, and vertical
wind direction. The data were collected at
seven elevations above ground: 10,35,91,
137,182, 243, and 304 m. The format of
the data base is presented, and a summary
is given of the analyses conducted in the
course of processing these data. These
analyses include checks for consistency
and suspect values. Also, analyses were
conducted to detect diumal and seasonal
trends in the time series of data. The goal
of these analyses was to aid in the assess-
ment of data integrity. Dimensional
analyses employing scaling lengths and
velocities were not performed, as these
were beyond the scope of laying a basic
foundation for future studies.
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 Pro-
ject Report ordering information at back).
Introduction
There are few meteorological data sets
having an extended period of record
available from tall towers. This document
summarizes one such meteorological data
set collected during the period 1975 to
1979 by the Meteorology Group of the
Savannah River Laboratory (SRL), Atomic
Energy Division, E.I. du Pont de Nemours
& Company. These data contain 15-min
averages and standard deviations of tem-
perature, horizontal wind speed and wind
direction, and vertical wind direction. The
data were collected on the WJBF tower at
seven elevations above ground: 10, 36, 91,
137, 182, 243, and 304 m.
This document is structured to serve the
needs of those aiming to employ these
data in analyses of their own and of those
reviewing the results gained already by
this initial review of the data. A brief
description is provided of the instrumen-
tation and data handling employed to
establish the original 15-min averages and
standard deviations of the various
meteorological elements. This discussion
and the summary of the flagging proce-
dures instituted during the review of the
data provide the technical information for
assessing the suitability of these data for
a particular investigation. A summary is
presented of the data processing accom-
plished by this study. Data descriptions
and formats are provided for the various
computer files established on the EPA
Sperry UNIVAC 1110 computer. These
tables will prove useful to those accessing
these files in later studies. The data were
analyzed for consistency and those values
that appeared suspect were flagged. In
most cases, the suspect values are at-
tributable to values below instrument
threshold or beyond instrument range. An
inspection of the flagging procedures will
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reveal that the intent was to identify the
most extreme values. Procedures are
outlined for estimating the surface fluxes
and certain other parameters typically
employed in meteorological analyses. A
summary is presented of the trends and
patterns seen in the course of the data
processing. Plots were developed depict-
ing the diurnal variation of the meteor-
ological elements for each month. The
goal of these analyses was to aid in the
assessment of data integrity. Dimensional
analyses employing terms such as mixing
height, surface friction velocity, or Monin-
Obukhov length were not performed.as
they were beyond the scope of this study.
The intent of this study was to lay the
groundwork for the succeeding analyses.
The WJBF-SRL Meteorological Facility,
is 11 km southeast of Augusta, GA, and
23 km southwest of Aiken, SC. The
365-m tower, the base of which stands
121 m above mean sea level, has been in
use as a meteorological tower since
October, 1965.
The WJBF tower is one of three TV-radio
towers near the rural community of Beach
Island, SC. There is no one dominant form
of land use in its immediate vicinity. Along
any given azimuth from the tower, the rol-
ling terrain varies with pine tree forests
(heights approximately 10 to 20 m),
pastures and fields, and clearings of waist-
high scrub and young saplings.
Two major topographical features are
the Savannah River and an intermittent
stream called Long Branch. The broad
Savannah River flows within 5.6 km to the
west and within 9.7 km to the south of the
WJBF tower. Long Branch flows from
northwest to southwest with its closest
approach about 610 m southwest of the
tower.
The terrain and ground cover in the
vicinity of the tower is similar to much of
the southeast piedmont region of the
United States. Study of the climatology of
these tower data should yield useful infor-
mation on conditions experienced by
sources of pollutants within this region.
Those studies of dispersion conducted
employing the tower data have not shown
the meteorological conditions to be
dominated by the rolling terrain and varied
land use. To the contrary, it has been found
that the similarity scaling relationships are
still useful descriptions even though such
relationships are applicable, strictly speak-
ing, to flat homogeneous terrain.
Procedure
As the data came from several sources
in different formats, the first step was to
convert the data into convenient formats
for the succeeding analyses. Those values
within the SRL tower data deemed
suspect were flagged in a manner that
retained access to the original values.
Suspect values within the National
Weather Service data typically could be
attributed to keypunch errors that were
easily identified by a comparison with ad-
jacent values in time or space. Those
values identified as keypunch errors were
replaced with corrected values.
Flagging Procedures for
WJBF Meteorological Data
As often occurs in the review of data
values from large sets, some values are
deemed of questionable validity. In such
cases, one has the choice of either
eliminating those values from the data set
or annotating them in some manner. The
latter procedure is often referred to as
"flagging." The reasons for flagging any
single value are legion. We have chosen to
flag questionable values by (1) adding
2000 to the original value and (2) assign-
ing a specific code word to the value. This
code word, when used with the ap-
propriate key, provides the reason for the
flagging. The user does not have to
decode the code word unless he wants the
reason for flagging. Since all the original
data values contain, at most, three digits
in front of the decimal, no significance was
lost by the addition of the 2000. The code
word was left blank for unflagged data
values. If the user wishes, the flagging can
be ignored altogether, and the original data
set can be rebuilt by subtracting 2000
from all flagged values.
Results and Discussion
Surface Parameter Analyses
Atmospheric dispersion is controlled by
turbulence in the air. Therefore, the param-
eters describing the scales of turbulence
are of fundamental importance in a
description of atmospheric dispersion. The
meteorological instrumentation necessary
to specify these scaling parameters direct-
ly is typically not available except during
research field studes. In lieu of such
measurements, the scaling parameters are
specified through the use of semi-
empirical relationships employing more
easily obtainable meteorological data. It
was not the purpose of this effort to
analyze the SRL tower data in terms of
these parameters. However, it was felt that
it would be worthwhile to explore, on part
of the data base, the specification of some
of these scaling parameters. Such an
analysis would provide insight into the dif-
ficulties to be encountered in specifying
the scaling parameters with the available
data.
The surface roughness length was
estimated to be 0.30 m using the longi-
tudinal turbulence intensity. This value is
reasonable considering the surface ground
cover and the site description. This value
of roughness length was used to develop
estimates of the surface fluxes. Com-
parison of the observed vertical and lateral
turbulence intensities with theoretical
estimates revealed no major inconsisten-
cies. We did find a group of erroneous
values for the standard deviation of the
horizontal wind direction, having values
below 2 degrees, that had gone unde-
tected when the flagging procedures were
developed. It was also found during these
latter comparisons that the procedure
employed for estimating the Monin-
Obukhov length L has a bias against
estimating L-values of about 15m. This is
considered of minor consequence. An
anomalous behavior in the turbulence
values for westerly wind directions was
traced to the wind shadow cast by the cup
anemometer on the bivane for wind direc-
tions between 269 and 285 degrees.
Diurnal Variations
In the course of assessing the tower
data for continuity and veracity, we found
it useful to develop analyses of the diurnal
variation of the meteorological elements.
The typical solution is to average all data
by hour of day. The sharp changes in time
and space are smeared by such a pro-
cedure. However, such averaged data are
useful for a first assessment of the trends
evident within a set of data.
For every other month starting with
February, the 15-min data values were
grouped into 2-h blocks, with 00-02 local
standard time as the first block. About
240 cases were possible in each 2-h block
at each height, a total of 8 (four 15 min
periods per hour) times the number of days
in the month. Missing and questionable
data would reduce this number.
In general, the developed plots revealed
the expected annual trends in the diurnal
patterns. Too much emphasis should not
be placed on the precise details in the pat-
terns or in the precise magnitudes of the
variables. These analyses are useful for
developing a sense of the seasonal trends
that occur in the structure and gradients
in time and space. One can also develop
some sense of the typical magnitudes to
be expected.
Seasonal Variations
After inspecting a number of the diurnal
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patterns for each month for each meteoro-
logical variable, characteristic (key)
features of these patterns were chosen for
analysis over the five-year period. As a
working criterion in the selection of these
features, those qualities were selected
that, if properly approximated, would
strongly promote an accurate description
of the observed diurnal patterns for each
month.
The key features selected for analysis
for each of the meteorological variables
follow.
Potential Temperature
10-m
average value
maximum value and hour of
occurrence
minimum value and hour of Conclusions
occurrence
Nocturnal structure
inversion strength when 10-m
minimum temperature occurs
The F-test results, comparing the above
two models, suggest that seasonal varia-
tions can be detected and characterized.
Those key features, shown to have a
significant seasonal variation within the
tower data, provide a standard for com-
parison in model evaluation studies. For in-
stance, if boundary layer meteorology
were simulated using routinely available
NWS data, a comparison could be made
to determine how well the simulated
meteorology describe the determined
seasonal variations. Objective statements
could be made whether the simulated
meteorology provided as precise a
characterization of the variations as that
determined with the available tower data.
Wind Speed
10-m
average value
maximum value and hour of
occurrence
minimum value and hour of
occurrence
Nocturnal structure
maximum value, height and time of
occurrence
gradient in the vertical between
maximum and 10-m value
Wind Direction Fluctuations
10-m
average value
maximum value and hour of
occurrence
minimum value and hour of
occurrence
Horizontal Wind Direction Shear
maximum value, height and time of
occurrence
An inspection of the time series of
values determined for each of the key
features suggested strong seasonal
dependence for some of the key features.
A procedure was established for deter-
mining a best fit sine wave to the key
feature values as an aid in assessing the
seasonal dependence. The period was as-
sumed to be one year.
As an alternative to a seasonal depend-
ence, one could hypothesize that no
significant seasonal trends exist. An F-test
can be used to test whether the variance
is significantly reduced in choosing be-
tween a seasonal or a nonseasonal model.
A summary is presented of the data
processing completed on the five-year
data set of meteorological tower data col-
lected by the Meteorology Group of the
SRL. This data set provides a unique op-
portunity to study micrometeorological
processes within the lower 300 m of the
atmosphere. The purpose of this docu-
ment is met if it provides potential users
of these data the information needed to
access the data files.
It is anticipated that users of these data
have access to the EPA Sperry Univac
computer. No plans have been made to
provide copies of the data for use on other
computer systems. Inquiries for gaining
access to the data should be addressed to:
Chief, Environmental Operations
Branch (MD-80)
Meteorology Division
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711.
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The EPA authors, John S. Irwin. Thomas M. Asbury, and William B. Peterson
are 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 "Description of the Savannah River Laboratory
Meteorological Data Base for 1975 to 1979," (Order No. PB 86-166 287; 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/600/S3-86/017
0000329 PS
0 S ENVIR PROTECTION AGENCY
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