NMMB- CMAQ 4km forecasting system in Houston: model simulation and evaluation

One of the most important values of an air quality forecasting system is to predict ground-level ozone concentrations under extreme chemical weather conditions and be able to issue health-related warning to the public in advance with enough lead times. The Houston area is well known for its high ozone events that occur frequently in late summer or early fall. This study represents an incremental process in building a limited domain fine resolution air quality forecasting system. It consists of coupling the National Weather Service meso-scale NMMB operational weather forecasting model with US EPA Community Multi-scale Air Quality model in an off-line manner. It has 2-tier nested domains. The CONUS is the parent domain in 12-km resolution and an inner nest over Houston and it surrounding area in 4-km resolution. Model evaluation focused on the inner domain is critical to validate the performance of this modeling system. In this evaluation, we focus on surface ozone and PM2.5 concentrations. Model verification utilized ground station, flight measurements, and satellite based data. Model performance under different meteorological and emission conditions were identified and studied.