NOAA and EPA have developed and operationally implemented a new ozone forecast capability, in response to Congressional direction. The NWS/ National Centers for Environmental Prediction (NCEP) North American Model (NAM) Weather Research and Forecasting Non-Hydrostatic Model (WRF-NMM) was implemented in June 2006 and is providing meteorological predictions for the EPA Community Multi-scale Air Quality (CMAQ) model to produce 48 h ozone predictions. The CMAQ system simulates various chemical and physical processes that are important for modeling atmospheric trace gas transformations and distributions.

This paper describes the improvements to and performance of the NOAA NAM-CMAQ weather and air quality modeling systems that are run on the NWS/NCEP operational computer for real-time air quality forecasting. For this presentation, two systems are tested and evaluated; the Eastern U.S Operational domain and the CONUS experimental domain run. The Eastern U.S. domain is loosely coupled in the vertical by interpolating needed fields from the WRF-NMM Hybrid coordinate to the CMAQ's Sigma-P coordinate, while a common NMM hybrid coordinate is employed for both models in the tightly coupled experimental CONUS forecasts. Both systems are run twice per day at 12 km horizontal resolution at 06 and 12 UTC with forecasts to 48 hours. Both Operational and experimental were run with gas-phase chemistry only, however, developmental research runs also were made over CONUS with the addition of aerosol processes.

A general model evaluation will be performed against the EPA AIRNOW observation network using the NCEP Forecast Verification Systems (FVS) for the various regions of the Country. The impact of the meteorological driver on CMAQ ozone forecasts will also be studied by comparing the impact of WRF meteorological forecasts on the CMAQ predictions for several cases when CMAQ was driven by both Eta and WRF. In addition, WRF and CMAQ predictions will be evaluated against observed vertical profiles of temperature, winds, moisture and ozone in the boundary layer and free troposphere .Finally, plans will be described that include the future transition of the NAM-CMAQ system with improved physical coupling and further testing of particulate forecasts for NCEP operations on regional and global scales.