Coupling of WRF with the Community Multiscale Air Quality (CMAQ) Mode

Daewon Byun

University of Houston

Currently, two distinct versions of Weather Research and Forecasting (WRF) model are under development by NCEP and NCAR. Within the next couple of years, NOAA/NWS will be replacing the current Eta model with the version of WRF that contains the dynamic core of the NWS non-hydrostatic mesoscale model (hereafter designated as WRF/NMM).  Recently NOAA (NWS and OAR) has been testing an initial capability for numerical air quality forecasting. The backbone of this initial capability is a computer modeling system based on the NWS Eta mesoscale meteorological forecast model and the NOAA/EPA Community Multiscale Air Quality (CMAQ) model.  Because the Eta model will be replaced by WRF/NMM in the near future, there is a need to build the air quality forecast capability by linking CMAQ with WRF/NMM.  The fully compressible governing set of equations used in CMAQ can maintain dynamic description of the WRF just by replacing the Jacobian defining the vertical coordinate transformation and by carefully writing out dynamic and thermodynamic variables.  In this presentation, I will discuss issues involved in linking CMAQ to the dynamics and grid structure of WRF/NMM.  We will contrast the different linkage methods between the WRF/NMM and WRF/EM.