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D. C. Wong et al.
to provide consistency with the meteorological processes. A coupler has been constructed to facilitate data exchange between the two models. Initial test simulations
show reasonable results when compared with observational data.
6.1 Introduction
Air quality modeling studies using the Community Multiscale Air Quality modelling
system (CMAQ) performed at the US EPA, are typically done on a regional scale. The
air quality model is driven by a meteorological model since it requires various fields
such as wind components, pressure, temperature, humidity, and many others as input.
The offline system (i.e. sequential simulation of meteorology followed by chemistry
and transport) carries a list of shortcomings [4] which drove the development of the
WRF-CMAQ two-way coupled model with direct aerosol radiative effects.
Studies have shown that pollutants are frequently transported over hundreds or
thousands of kilometers to affect specific receptors. Satellite images have shown a
smoke plume from the 2002 Alaskan wild fires was transported down to southern
Texas and then advected toward the eastern seaboard. Researchers employ domain
nesting (i.e. the main study domain is enclosed by a larger domain of coarser resolution), which is usually repeated two to four times, to bring in influence from long
distance sources. However, nesting for air quality modeling is usually applied in one
direction only. Recently, CMAQ has been extended to the hemispheric scale [2] to
help address long range transport issues.
Boundary conditions are a major challenge for regional scale modelling. In practice, boundary conditions are usually created from a global chemistry model such as
GEOS-Chem. To make this global model output suitable to serve as boundary conditions for a regional model is not a straightforward matter. It involves a number of
steps such downscaling, map projection conversion, and chemical species mapping.
These steps introduce various degrees of error.
Currently in the offline version of CMAQ or in the WRF-CMAQ coupled model,
chemical species transport processes take place within CMAQ and the advection
and diffusion algorithms are not the same as in the meteorological model. Thus,
this inconsistency is an additional concern in CMAQ modeling. This new development, coupling a global meteorological model, MPAS-A, with an air quality model,
CMAQ, focuses on addressing the above issues: boundary conditions and transport
inconsistency.
D. C. Wong et al.
to provide consistency with the meteorological processes. A coupler has been constructed to facilitate data exchange between the two models. Initial test simulations
show reasonable results when compared with observational data.
6.1 Introduction
Air quality modeling studies using the Community Multiscale Air Quality modelling
system (CMAQ) performed at the US EPA, are typically done on a regional scale. The
air quality model is driven by a meteorological model since it requires various fields
such as wind components, pressure, temperature, humidity, and many others as input.
The offline system (i.e. sequential simulation of meteorology followed by chemistry
and transport) carries a list of shortcomings [4] which drove the development of the
WRF-CMAQ two-way coupled model with direct aerosol radiative effects.
Studies have shown that pollutants are frequently transported over hundreds or
thousands of kilometers to affect specific receptors. Satellite images have shown a
smoke plume from the 2002 Alaskan wild fires was transported down to southern
Texas and then advected toward the eastern seaboard. Researchers employ domain
nesting (i.e. the main study domain is enclosed by a larger domain of coarser resolution), which is usually repeated two to four times, to bring in influence from long
distance sources. However, nesting for air quality modeling is usually applied in one
direction only. Recently, CMAQ has been extended to the hemispheric scale [2] to
help address long range transport issues.
Boundary conditions are a major challenge for regional scale modelling. In practice, boundary conditions are usually created from a global chemistry model such as
GEOS-Chem. To make this global model output suitable to serve as boundary conditions for a regional model is not a straightforward matter. It involves a number of
steps such downscaling, map projection conversion, and chemical species mapping.
These steps introduce various degrees of error.
Currently in the offline version of CMAQ or in the WRF-CMAQ coupled model,
chemical species transport processes take place within CMAQ and the advection
and diffusion algorithms are not the same as in the meteorological model. Thus,
this inconsistency is an additional concern in CMAQ modeling. This new development, coupling a global meteorological model, MPAS-A, with an air quality model,
CMAQ, focuses on addressing the above issues: boundary conditions and transport
inconsistency.