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Central California Ozone Study (CCOS) Model Verification
The Central California Ozone Study (CCOS) is an ongoing program of the
California Air Resources Board (CARB) whose goal is to develop better
meteorological and aerometric observational data bases, as well as
numerical simulation models, to more completely understand and predict
urban and regional-scale ozone episodes. These observations and models
will form the scientific basis for the development of appropriate
emission control strategies to help California meet regulatory
requirements for state and federal 1-hour as well as federal 8-hour
ozone standards.
Field Season
The CCOS observational field program operated from June 1 through
October 2, 2000. During the CCOS 2000 field program, extensive
observations were collected in central California to document high ozone
episodes and the meteorology that is associated with them. During the
field phase of CCOS, ETL deployed a network of 15 wind profilers
across California. This network was supplemented by an additional
10 profilers provided by other agencies, for a total of 25 wind profilers
in the network. In addition, ETL deployed 9 sodars, 20 surface
meteorological stations, and instrumented two towers with
meteorological instruments.
Analysis
ETL is presently working with CARB on both the analysis of these
meteorological data, and in the development and running of a
meteorological numerical simulation model (MM5). The goal of the
data analysis is to identify the dominant meteorological processes
affecting the central valley, and to asses the impact of these processes
on ozone concentrations. The goal of the numerical simulation study is
to provide accurate, high-resolution meteorological simulations
(a 4 km grid with 50 vertical levels) that will then be used by CARB
to drive a regional air quality model. The observational data will be
used to evaluate the meteorological model, as well as to optimize model
skill through four-dimensional data assimilation. As part of the
modeling study, three different turbulence/boundary layer
parameterization schemes (ETA, MRF, and Gayno-Seaman) are
being evaluated.
Regional Meteorology
Meteorological phenomena in the central California region that are known
to have a pronounced impact on ozone concentrations include
- the sea-breeze, which can bring cooler, moister, and lower ozone
concentration air as it propagates inland;
- flow through the San Francisco Bay area, which is the principle
inflow to the Central Valley, and the split of this flow, which determines
the relative inflow into the Sacramento and San Joaquin Valleys;
- nocturnal low-level jets, which can rapidly transport boundary
layer pollutants along the Central Valley;
- mesoscale eddies (the Schultz, Fresno, and Bakersfield) which
can re-circulate ozone and its precursors;
- slope flows, which result in transport in or out of the valleys,
support boundary layer venting along mountain crests, and produce subsidence
or ascending motion over the valleys; and
- the depth of the atmospheric boundary layer, which is of critical
importance to air quality, as it determines the depth through which
pollutants are vertically mixed.
Intensive Operating Periods (IOP's)
During the CCOS 2000 field program several moderately high ozone
episodes occurred, the most interesting of which are the June 14-15,
July 29-August 3, and September 16-22 intensive operating periods (IOP's).
These three IOP's are being analyzed and modeled by ETL. A
model evaluation web site
has been developed which displays both observations, model predictions,
and the difference between these two. Presently, results from IOP2
(30 July - 2 Aug) are displayed on the web site.
ETL Team Members
Members of the ETL team that are contributing to the CCOS analysis program, and their areas of expertise, are:
Jian-Wen Bao
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applications/development and evaluation/verification of NWP models
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Dave Costa
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data base management and graphics development
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Clark King
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meteorological analysis
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Jessica Koury
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graphics and web development
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Ann Keane
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web development
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Sara Michelson
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applications/development and evaluation/verification of NWP models
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David White
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meteorological analysis
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Robert Zamora
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applications/development and evaluation/verification of NWP models
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Jim Wilczak
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team lead
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