 Air Quality forecast using WRF/NMM-CMAQ during the TexAQS Pius Lee 1* , Stuart McKeen 2 , Jeff McQueen 3 , Daiwen Kang 4 , Marina Tsidulko 1 , Sarah Lu 1 , Hsin-Mu Lin 4 , Geoff DiMego 3 , Nelson Seaman 5 , and Paula Davidson 5 1. INTRODUCTION During 2003, NOAA and the U.S. EPA signed a Memorandum of Agreement to work together to develop a National Air Quality Forecasting (AQF) capability. To meet this goal, NOAA’s National Weather Service (NWS), the Office of Atmospheric Research (OAR) and the U.S. EPA developed and evaluated a prototype O 3 forecast capability for Northeastern U.S. (Davidson et al, 2004). The NWS/ National Centers for Environmental Prediction (NCEP) North American Meso-scale (NAM) model (Rogers et al, 1996; Janjic 2003) at 12 km was used to drive the EPA Community Multi-scale Air Quality (CMAQ) model (Bynn et al, 1999) to produce up to 48 hour O 3 predictions. From the outset, plans have called for the AQF capability to include particulate matter forecast guidance also. The importance of such a capability is obvious. High volume of particulate matter suspended in the atmosphere posts hazard to health and impairment to visibility. Several regions in the country have recently reported haze and degraded visibility for prolonged period of time (e.g., Taubman et al, 2004). Moreover, every year, upwards of 40,000 premature deaths in the US are attributed to exposure to airborne particulate matter (Kaiser, 2005). A developmental version of the AQF capability (Lee et al, 2006), hereafter dubbed as AQF- , that includes the predictions of airborne ____________________ *Corresponding Author Address: Pius Lee, NCEP/EMC, W/NP22 Room 207, 5200 Auth Road, Camp Springs, MD 20746-4304; pius.lee @noaa.gov 1 Scientific Applications International Corporation, Beltsville, Maryland. 2 CIRES & NOAA/ESRL/GSD, Boulder, CO. 3 National Centers for Environmental Prediction, NOAA/NWS, Camp Springs, Maryland. 4 Science and Technology Corporation, Hampton, VA. 5 Office of Science and Technology, National Weather Service, Silver Spring, MD. fine particulate matter (PM2.5) has been tested during the summer of 2006. It covers the CONtinental US (CONUS) with daily 48 h predictions. The Texas Air Quality Study (TexAQS) 2006 is an intensive field campaign aimed to better understand the sources and processes responsible for the formation and distribution of tropospheric O 3 and aerosols (TCEQ, 2006). The campaign was conducted between early August and mid October 2006. Data collected during TexAQS by multiple air and land based stations provided a unique opportunity to verify the forecast quality of AQF- . 2. Model CONFIGURATIONS The NAM meteorological model is also known as the Weather Research and Forecasting/ Non-hydrostatic Meso-scale Model (WRF/NMM). It provides met and hydrometeor fields to CMAQ to derive the transport, and transformation, as well as the meteorological dependent emission strengths, of the various atmospheric gaseous and aerosol species and their precursors. a. WRF/NMM Model The model is the successor of the NCEP Eta model. The three major improvements of WRF/NMM from its predecessor are: (1) non- hydrostatic approach, (2) adoption of a 60 levels, upper-levels pressure-surfaces, and lower-levels terrain following -p hybrid coordinate, and (3) conform to the WRF data interface infrastructure. Otherwise the horizontal griding and physics packages are rather similar to those used in the Eta model (Rogers et al, 2005, Ferrier et al, 2005); namely, they both use Arakawa E-grid horizontal stencil; Noah unified 5-layer land and surface model; Mellor-Yamada- Janjic planetary boundary layer closure scheme; Ferrier cloud microphysics; and Betts-Miller- Janjic convective mixing scheme. b. CMAQ Model