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| Titel |
Development and Evaluation of the 2-Way Coupled WRF-CMAQ Model |
| VerfasserIn |
Jonathan Pleim, Rohit Mathur, David Wong, Shaocai Yu, Frank Binkowski |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250053895
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| Zusammenfassung |
| A new 2-way coupled meteorology and air quality model composed of the Weather Research
and Forecasting (WRF) model and the Community Multiscale Air Quality (CMAQ) model is
being developed and tested by the Atmospheric Modeling and Analysis Division at
the USEPA. The new model system runs as a single executable with 2-way data
communication between the WRF and CMAQ components via IOAPI_3 buffer
files. This design requires minimal changes to either model which allows for easy
updating and maintenance of compatibility with the “off-line” system. The main
purposes of the coupled model are: 1) to allow efficient frequent data exchange for
high resolution (down to 1 km grid cell size) simulations, 2) to allow feedback
of gases and aerosols from CMAQ to WRF where they can affect radiation and
microphysics processes, 3) to allow for more integrated treatment of chemical and physical
processes.
The direct effects of aerosols on shortwave radiation and the direct effects of tropospheric
ozone on longwave (LW) radiation have been implemented in the CAM and RRTMG
radiation schemes in WRF. A new Mie scattering algorithm has been developed for a wider
range of wavelengths including LW. New model simulations of the 2-way WRF-CMAQ using
the latest versions of both models have been evaluated for a summer month in the eastern US
and an outbreak of wild fires in California in 2008. Comparisons between runs with and
without direct feedbacks show significant impacts on solar radiation, 2-m temperature, PBL
height, and ozone and PM2.5 concentrations, especially in areas affected by smoke
plumes.
The 2-way WRF-CMAQ also includes an experimental implementation of indirect effects
where aerosols from CMAQ are activated as cloud condensation nuclei which determine the
droplet number concentration for the cloud microphysics model. The resulting effective
droplet radius is used in the radiation model to compute cloud optical properties. The indirect
effects are being tested by evaluation of cloud radiative forcing compared to satellite
measurements.
The 2-way WRF-CMAQ is being evaluated for its ability to accurately represent changes in
direct and indirect radiative forcing due to large emission reductions of aerosol
precursors, such as SOx and NOx, over the last 20 years in North America and
Europe. These emission reductions present a unique opportunity for testing coupled
meteorology and chemistry modeling systems. This study involves 20 years of continuous
simulation at high-resolution (12 km) over North America using historical emission
inventories developed by the USEPA. Aerosol concentrations and ground based
radiation measurements will be used for evaluation of model response to emissions
trends. |
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