Direct linkage of meteorological data for WRF-NMM/CMAQ coupling

The NOAA-EPA air quality Forecast system (AQF), operational at NCEP, is based on the coupling of North American Mesoscale (NAM, formerly Eta) meteorological model and the Community Multiscale Air Quality (CMAQ) atmospheric chemistry transport model. The NAM provides the necessary meteorological data for input to the CMAQ. Because the NAM and CMAQ use different horizontal and vertical coordinate systems and computational grid structures, an interface processor, PREMAQ, was developed to transform various meteorological fields from the NAM's coordinate and grid structure to forms compatible with CMAQ input requirements. PREMAQ also contains the requisite functionality to ingest and process (following the SMOKE emissions processing system) emission inventory data in forms compatible with CMAQ input requirements. In the initial implementation of this system a series of processors performing horizontal and vertical interpolation is used between the NAM and PREMAQ.

WRF-NMM, the next generation of mesoscale forecasting system at NCEP, is currently under testing and will soon become the NAM. To reduce the errors associated with interpolation and to improve the linkage between the NAM and CMAQ, efforts are underway to build a system where both models use the same vertical and horizontal coordinate and grid structures. This involves changes both the PREMAQ and the CMAQ model. The revised PREMAQ will incorporate algorithms to compute any additional fields not directly output from the WRF-NMM, but are required for the CMAQ. These data requirements and methods employed will be presented.

Disclaimer The research presented here was performed under the Memorandum of Understanding between the U.S. Environmental Protection Agency (EPA) and the U.S. Department of Commerce's National Oceanic and Atmospheric Administration (NOAA) and under agreement number DW13921548. This work constitutes a contribution to the NOAA Air Quality Program. Although it has been reviewed by EPA and NOAA and approved for publication, it does not necessarily reflect their policies or views.