We have conducted air quality modeling studies in the Houston-Galveston Area (HGA) with Models-3 Community Multiscale Air Quality (CMAQ) software.

One key problem of many air quality models is finding accurate initial and boundary conditions. In order to obtain better initial and boundary conditions, the CMAQ model is run for a spin-up time of its model domain. Afterwards the simulation is restarted with initial/boundary conditions from the last day of spin-up time. To further improve the model results regional air quality modeling such as Texas urban air quality is used to get more reasonable initial/boundary conditions. To do this work, we must make sure the global and regional air quality models are consistent by examining their parameters such as coordinate definition, horizontal/vertical interpolation, dynamical consistency and compatibility of chemical mechanisms.

To use global air quality modeling, the Goddard Earth Observing System-CHEMistry (GEOSCHEM) model can be used and it is required in order to link between CMAQ and GEOSCHEM. GEOSCHEM, which was developed by the Harvard air-chemistry research group, is a 3-dimensional global chemistry air quality model with O3-NOx-Hydrocarbon chemistry. To link CMAQ with GEOSCHEM, it is necessary to do coordinate conversion, horizontal/vertical interpolation and chemical species mapping.

Linking CMAQ with GEOS-CHEM (Slides)