P23 A study of particulate matter speciation improvement and aerosol radiative feedback on meteorology over US by a GSI-WRF/Chem coupled three-dimensional variational assimilation system

Chen, Dan, Zhiquan Liu, C. Schwartz, and Hui-Chuan Lin, National Center for Atmoshperic Research

The Gridpoint Statistical Interpolation (GSI) three-dimensional variational (3DVAR)

data assimilation (DA) system coupling with the WRF/Chem model was utilized to study the aerosol direct and semidirect radiative feedbacks on the regional atmosphere in Aug 2012, when a wild fire originated from Western US sent smoke eastern ward accorss United States during the period of Aug 14-16. The total 550 nm aerosol optical depth (AOD) retrievals from Moderate Resolution Imaging Spectroradiometer (MODIS) sensors, and the conventional PrepBUFR meteorological data from National Centers for Environmental Prediction (NCECP) were assimilated. Two modeling experiments were conducted: one only assimilated conventional PrepBUFR meteorological data (MET_DA), the other assimilated PrepBUFR and MODIS AOD simultaneously (MET_AOD_DA). The results indicate that the MET_AOD_DA shows a distinct improvement in the concentrations of not only surface PM2.5 but also organic carbon (OC) during the fire event compared with the case without AOD assimilation. The direct radiative forcing by aerosol caused changes in temperature and wind speeds in fire occurrence region. The semidirect forcing also caused the spatial distribution changes of precipitation in the cloudy Eastern US region. Preliminary results from these simulations will be presented at the workshop.