United States
Environmental Protection
Agency
Atmospheric Sciences
Research Laboratory
Research Triangle Park NC 27711
'i r*
Research and Development
EPA/600/S3-87/048 Feb. 1988
v>ERA Project Summary
Developments in National
Weather Service
Meteorological Data Collection
Programs as Related to EPA Air
Pollution Models
Thomas E. Pierce and D. Bruce Turner
During the next decade, the
National Weather Service (NWS) wili
be upgrading its meteorological
instrumentation and data
dissemination procedures. Because
these changes will affect the
operation of the U.S. Environmental
Protection Agency's (EPA) air
pollution models, this project has
been undertaken to report on
proposed changes and to
recommend how to make optimal use
of the new NWS data products. New
instrumentation will include
automated surface observation
systems, next generation radar, and
remote profilers. Data dissemination
is being upgraded with an automated
weather interactive processing
system, the conversion of data tapes
to an element format, and the
introduction of data formats that are
compatible with personal computers.
Complete descriptions of existing
and new formats that are applicable
to EPA air pollution models are given
in the Appendices. To maximize the
usefulness of NWS meteorological
data, the following actions are
recommended: (1) adapt the EPA
meteorological processors to read
the new data formats and upgrade
them to incorporate advances in
diffusion meteorology; (2) encourage
the collection of meteorological data
specific to diffusion modeling and
investigate the feasibility of
collecting some of these data at NWS
sites; (3) improve the handling and
formatting of NWS data for regional-
scale models; and (4) maintain active
communication with the National
Climatic Data Center (NCDC).
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
One of the principal inputs to an air
pollution model is meteorological data.
Collecting and archiving the data pose a
challenge to those involved in diffusion
modeling. The Nuclear Regulatory
Commission (NRC) and the
Environmental Protection Agency (EPA)
have addressed this problem of
meteorological data quite differently. The
NRC requires that nuclear installations
collect comprehensive meteorological
data, including temperature differences,
hourly average winds, and turbulence
fluctuations. These measurements are
usually taken on masts at heights ranging
from 30 to 100 m. In some localities,
such as near a large body of water,
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multiple meteorological masts are
required. In contrast, EPA regulates a
greater number and many more types of
sources than the NRC. Because it is
impractical for every potential emitter of
air pollution to operate a comprehensive
on-site meteorological monitoring
program, EPA has traditionally relied on
meteorological data collected by the
National Weather Service (NWS). EPA's
models use simplistic characterizations
of diffusion meteorology using only a few
measured NWS meteorological variables.
For example, the rate of dispersion is
determined by a Pasquill stability class
as estimated from routine observations of
wind speed, cloud cover, and ceiling
height. Hourly estimates of plume rise,
dilution, and transport direction are
based on a single 2-minute average
wind value reported by an observer on
the hour.
During the past few years, the NWS
has started to modernize its
meteorological instrumentation and data
dissemination systems, and EPA has
begun efforts to use additional
meteorological information to
characterize diffusion. Upgrades in new
instrumentation will include automated
surface observation stations (ASOS),
next generation radar (NEXRAD), and
remote profilers. Data dissemination will
be improved with the operation of an
automated weather interactive
processing system (AWIPS) and perhaps
with a modern climatological data
distribution system (NOAANET). The
focus of this project is to assess how
these changes in NWS meteorological
data will affect EPA air pollution models.
In particular, this project is intended to
inform model users and developers on
likely changes and to recommend
upgrades in meteorological processors in
order to effectively accommodate data
from new instruments and in different
formats.
Current Requirements
Air pollution models in EPA can be
broken down into two basic areas:
UNAMAP models and regional models.
In general, UNAMAP models are used by
the public for regulatory modeling. It is
estimated that several hundred
organizations in the United States use
UNAMAP models. Regional models tend
to be larger and more complicated than
UNAMAP models. They are either used
for research and development or for
planning emission reduction strategies
across several states. Models such as
the regional model for acid deposition
(RADM) and the regional oxidant model
(ROM) are being used in making
important policy decisions. Both types of
models depend on NWS meteorological
data.
UNAMAP stands for the User's
Network for the Applied Modeling of Air
Pollution. It began in 1973 to provide the
EPA modeling community ready access
to models for estimating air quality
impact from proposed and existing
sources of air pollution. The latest
version of UNAMAP, version 6, was
released in 1986 and contains over 24
models and meteorological processors.
The UNAMAP models listed in Table
1 are either short-term or long-term
models. Short-term models use hourly
meteorological data to estimate air
pollution concentrations for time periods
ranging from 1 hour to 1 day. Long-
term models use climatological
frequency distributions of wind speed,
wind direction, and stability class to
estimate air pollutant concentrations for
seasonal or yearly periods.
As shown in Table 1, many of the
UNAMAP models use meteorological
data in special formats as available from
the National Climatic Data Center
(NCDC) in Asheville, North Carolina. The
four currently-used data formats are
summarized in Table 2.
Two of the UNAMAP models,
MESOPUFF-2 and PLUVUE-2, are
regional models. They require more data
than the other UNAMAP models.
MESOPUFF-2 requires surface and
upper-air data from many locations
within an area. Its meteorological
preprocessor, MESOPAC, accepts data
in the TD-1440 and TD-9689 formats.
PLUVUE-2 has similar data
requirements except it does not have a
preprocessor for manipulating
meteorological data into a specific
format.
Other regional models used by EPA
include RELMAP, ROM, and RADM.
Most of these models are undergoing
research and development, and their
meteorological processors can be
updated as new and improved
meteorological data become available.
Their data needs currently are similar to
MESOPUFF except that RELMAP
requires precipitation amounts for one
degree latitude by one degree longitude
areas. RADM estimates precipitation
amounts using its own dynamic
prognostic meteorological model
because adequate precipitation data do
not exist for objective analysis.
Proposed NWS Revisions
The NWS is modernizing its
observational systems and data
dissemination procedures. Existing NWS
instrumentation has not been significantly
modified for 25 years and is rapidly
approaching obsolescence. Furthermore,
the current observational process is quite
labor-intensive and requires a large
expenditure of funds. Technology now
exists for automated measurements of
surface and upper-air weather variables.
In addition, the advantages of Doppler
radar have been clearly demonstrated,
especially for severe weather application.
These new systems will generate
additional data that will require enhanced
data handling capabilities. The currenl
AFOS system uses 1970s technology
and is overburdened in its data handling
and processing requirements. Also, the
NCDC is striving to meet the needs ol
new data formats and the increasec
amount of data that will be collected ir
the near future.
Advances are taking place in surface
observations, upper-air observations
and radar. Current surface observatior
platforms will be replaced by an ASOS
The upper-air rawinsonde system wil
be supplemented by remote profilers
Radars are being replaced by Dopple
radar in the NEXRAD project.
The NWS plans for ASOS to be n
operation by the early 1990s. ASOS wi
be implemented in one of two levels
basic or unmanned. In the unmannei
level, ASOS systems will be installed a
sites which currently do not have .
meteorological observation system
ASOS will therefore provide extensiv
surface meteorological measurements i
locations where very little or n
information has been available. In th
basic level of service, ASOS will b
installed at existing weather reportin
stations. Initially, however, on-sit
observers will augment the system b
reporting additional cloud information an
special remarks. At some location:
where an observer is available less tha
24 hours a day, ASOS will run in a
unmanned mode when the observer i
not available. In all, about 1500 ASO
sites are planned for the next 10 years.
ASOS uses recent advances i
meteorological instrumentation. A las<
ceilometer will replace the current 2!
year-old rotating beam ceilometer. Th
laser ceilometer can measure clou
bases through precipitation and cz
detect cloud layers up to 12,000 fee
Visibility measurements will be taken wi'
a forward-looking visibility meter. Wi
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Table 1. Meteorological Requirements for UNAMAP (Version 6) Models
Model
Averaging Meteorological Format
Time
processor
BLP
RAM
ISCST
MPTER
CRSTER
MPTDS
COMPLEXI
Hourly
Hourly
Hourly
Hourly
Hourly
Hourly
Hourly
RAMMET
RAMMET
RAMMET
RAMMET
RAMMET
RAMMET
RAMMEr
TD-1440/9689
TD-1440/9689
TD-144019689
TD-1440/9689
TD-1440/9689
TD-1440/9689
TD-1440/9689
CALINE-3
INPUFF
PEM-2
PLUVUE-2
HIWAY-2
PAL-2
APRAC-3
PBM
MESOPUFF-2
TUPOS
SHORTZ
PTPLU-2
Hourly
Hourly
Hourly
Hourly
Hourly
Hourly
Hourly
Hourly
Hourly
Hourly
Hourly
Hourly
None
None
None
None
None
None
None
PBMMET
READ56/MESOPAC
MPDA
METZ
None
Unique
Unique
Unique
Unique
Unique
Unique
Unique
TD-1440/9689
TD-144015600
TD-
1440/5600/onsite
TD-
144019689/onsite
none-required
CDM-2
ISCLT
VALLEY-
LONGZ
Long-term
Long-term
Long-term
Long-term
None
None
None
None
STAR
STAR
STAR
STAR
"RAMMET is a generic name for EPA short-term meteorological
processors.
also predict 24-hour average concentrations.
the eventual automation of ASOS, a laser
weather identifier is being developed.
The current design employs a light-
emitting diode weather identifier
(LEDWI). The LEDWI can discriminate
between rain, snow, and drizzle and can
estimate their intensities. However, it
cannot discriminate between hail and ice
pellets. Other instruments being updated
include the hygrothermometer and the
windvane.
ASOS will have the capability of
storing data on-site and will connect
with the existing data dissemination
network. Current plans are for hourly data
summaries to be stored on-site for 30
days and 1-minute data to be stored up
to 8 hours. Eventually, the data from
ASOS will be disseminated via the
AWIPS and archived at the NCDC.
Table 2. Meteorological Data Formats Used with UNAMAP (Version 6) Models
NCDC Format Identifier Description
TO-1440
TD-5600
TD-9689
TD-9773
Hourly surface observations
Twice-daily rawinsonde observations
Twice-daily mixing height estimates
STAR data-joint frequency distributions
of wind speed, wind direction, stability class
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Despite its advantages, ASOS poses
potential shortcomings for air pollution
models. At unmanned sites, cloud
information will be available only to
12,000 feet. Current EPA meteorological
processors require opaque cloud cover
for stability estimates. However, the
ASOS program office intends to maintain
observers at primary locations so that
certain information such as the upper-
level cloud cover can be reported.
Unfortunately, current plans by the NWS
state that hourly values of meteorological
variables will be based on only 2-
minute data averages collected on the
hour. Since data will be sampled every
minute, true hourly averages (especially
of winds) could be obtained at little
additional cost. However, this averaging
and archival of hourly data requires a
commitment of funds that currently does
not exist.
Since World War II, rawinsondes have
been used to measure the vertical
structure of wind, temperature, moisture,
and pressure in the atmosphere.
Although the system is well established,
some minor improvements are being
implemented. Microprocessors are being
installed at each rawinsonde site which
will automate data collection and perform
many of the quality assurance checks.
This should result in greater data capture
and improved data quality. The
microprocessors coupled with a redesign
in the rawinsonde package will yield
more frequent measurements. Instead of
60 seconds, data will be archived for
every 30 seconds of ascent, thus
providing improved resolution of vertical
measurements. Also, data measured
every six seconds will be archived at
each site for up to six months.
For years, rawinsondes have not
provided upper-air data in a temporal
and spatial resolution desired by
numerical weather prediction and air
pollution modelers. Currently, upper-air
data are available every 12 hours and
only at selected stations. The profiler
system is designed to fill in these
temporal and spatial data gaps for
weather forecasting purposes.
The profiler is a ground-based
remote sensing system designed to
measure wind, temperature, and
moisture profiles above a given site
during all weather conditions. It consists
of two subsystems: a wind profiler and a
thermodynamic profiler. The wind profiler
is a UHF (frequency currently
established at 405 MHz) clear-air radar
which is sensitive to backscatter from
radio refractive-index irregularities
caused by turbulence. Winds with the
profiler are determined from Doppler
shifts of the backscattered signal. The
thermodynamic profiler used for
measuring temperature and moisture
consists of six channels of a radiometer
which measures thermally emitted
electromagnetic energy.
Like the ASOS program, the profiler
network poses some potential problems
for air pollution modelers. The lower limit
of measurement for the 405 MHz wind
profiler is 0.5 km. This limitation would
be a detriment to boundary layer models
which require lower-level winds. The
NWS has indicated that it is considering
to collocate acoustic Doppler sounders
along with the wind profilers to provide
lower-level winds. However, these plans
require further investigation. With the
thermodynamic profiler, temperature and
moisture data will be measured up from
the surface, but the accuracy of these
measurements will decrease with height.
Satellite sensing data is expected to
augment this data at upper levels.
Preliminary tests of the radiometric
measurements indicate that while the
temperature and moisture profiles are
averaged quite accurately, the
radiometer fails to detect rapid changes
in these parameters. Research is
continuing on how to integrate
information from the wind profiler and
other data sources to the temperature
and moisture readings. Therefore, while
it will be beneficial to have hourly vertical
profiles of temperature and winds, much
work remains to be accomplished with
the profiler to obtain the data in sufficient
vertical resolution for air pollution
modeling.
Another advanced system planned for
deployment in the 1990s is NEXRAD.
Like ASOS, it is the culmination of years
of research in an effort to modernize
instrument systems. NEXRAD is a
Doppler radar which provides increased
range and resolution of reflectivity
patterns. It also can estimate wind
velocities within precipitating clouds.
While its primary purpose is for severe
storm detection and tracking, its gridded
precipitation estimates should assist in
regional-scale air pollution modeling.
The NCDC each day handles
hundreds of requests for data. Six staff
meteorologists interact with users to
determine the data needs for each user.
The number of data requests and the
amount of data continue to grow at a
staggering pace. The center handles
over 20,000 requests for data per year. It
also has to maintain a tape library of over
30,000 magnetic tapes which grows
weekly. Because of this huge amount of
data, NCDC has started to modernize its
operation.
Modernization activities at NCDC
include an increased use of Personal
Computers (PCs) and the introduction of
the element format. Several data formats
are available on floppy diskette. These
include TD-1440 surface data, TD-
3280 surface data, TD-9689 mixing
height data, and TD-9773 STAR data.
As PCs gain favor among the air pollution
modeling community, the sale of floppy
diskettes by NCDC will likely grow.
Thus far, the new element formats
(TD-3280 and TD-6200) have not been
used in EPA air pollution modeling.
Although they have been available since
1984, changes in computer codes for
EPA meteorological processors take time
and money. However, discussions with
NCDC have revealed that obtaining the
same data in TD-3280 format instead of
TD-1440 reduces costs by about 40
percent. NCDC is basically set up on a
cost reimbursable basis -- they charge
what it costs them to generate the data.
Because data are stored in the element
format, it is advantageous to obtain the
data in the new format.
The advent of new observational
systems in the NWS presents additional
challenges to NCDC. NCDC has made
some effort on establishing formats for
NEXRAD and profilers. Archiving data for
NEXRAD will be a problem because of
the amount of gridded data. The amount
of data consists of gridded values (for 1
km by 2 km areas) every 5-15 minutes
for up to 25 variables. Clearly, this is a
large amount of data and needs to be
maintained in a logical manner. Because
profilers are still undergoing
development, their data are being stored
by NOAA's Environmental Research
Laboratory in Boulder, Colorado.
Eventually, the profiler data need to be
added to the national archive, but no
arrangements for archiving the data have
yet been made.
Summary and
Recommendations
This project began as an attempt to
understand how data formats from the
National Climatic Data Center (NCDC)
were changing and how these changes
would impact EPA's meteorological
processors. While investigating these
changes, we learned of new advances in
meteorological instrumentation and data
dissemination which potentially car
benefit EPA's air pollution models.
For EPA to best accommodate the
planned changes to NWS observatior
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ind data dissemination programs and the
planned changes to NCDC's data
formats, we offer the following
recommendations:
(1) Recognizing that EPA's
meteorological processors will need to
be modified to handle new NCDC data
formats, they should also be upgraded
to incorporate our more advanced
knowledge of diffusion meteorology.
This upgrade could also serve as a
catalyst for incorporating more advanced
modeling techniques into air pollution
models. It should be noted that such
efforts have begun with the development
of the Meteorological Processor for
Diffusion Analysis (MPDA) and the
Turbulence Profile Sigmas (TUPOS)
model.
(2) EPA should encourage the
collection of meteorological data
specific to diffusion modeling and
should investigate the feasibility of
collecting some of these data at NWS
sites. As recommended by an expert
panel in 1981, additional meteorological
variables such as horizontal fluctuations
of wind direction (06), harmonic mean
wind speeds, low-level temperature
gradients, and total solar radiation should
be collected for air pollution modeling. It
is promising to note that EPA recently
provided guidance for collecting some of
these variables at on-site measurement
programs. Not all air pollution modeling
applicants, however, will have access to
an extensive meteorological monitoring
program and will have to depend on
NWS data. Therefore, EPA should
actively coordinate NWS meteorological
data collection programs through the
Office of the Federal Coordinator. In
particular, it is advisable that EPA
maintain vigorous participation in the
Working Groups for Automated Surface
Observations, Profiler Systems, and
Radar Meteorological Observations.
Perhaps with funding from appropriate
organizations and cooperation with the
NWS, additional meteorological data for
diffusion modeling can be collected at
NWS sites.
(3) The formatting and handling of
meteorological data for regional-scale
models should be improved. Regional-
scale models require vast amounts of
surface, upper-air, and satellite data.
Because these models operate
sequentially, data must be sorted by
hour. Unfortunately, NCDC data are
sorted by station and not by hour.
Consequently, much effort goes into
generating a data set in the appropriate
format. Two options which could be
investigated include the development of
a new NCDC data format and direct
access and storage of NWS observations
by EPA.
(4) The Environmental Operations
Branch (EOB) should maintain active
communication with NCDC. In
performing this study, it became quite
apparent that NCDC is willing to be
responsive to the needs of the air
pollution modeling community. By
improving communication with NCDC,
EOB can more effectively inform users
about changes in data formats. One
possibility is to develop a users' guide
describing meteorological data
requirements for UNAMAP models. The
guide would also provide information on
how to order meteorological data from
NCDC, and it could serve as a valuable
reference manual for NCDC
meteorologists when dealing with air
pollution modeling clients.
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