Impact of Aerosols on East Asian Air Quality during the EAST-AIRE Campaign

WRF-Chem simulations were performed for the March 2005 EAST-AIRE field campaign in eastern China to investigate the direct effects of aerosols on surface radiation and air quality.  Domain-wide, WRF-Chem showed a decrease of 20 W per square meter in surface shortwave (SW) radiation due to the aerosol direct effect (ADE), consistent with observational studies. The ADE caused 24- hour surface PM2.5 to increase by 2-10% with largest increases in southern China and the Sichuan Basin, and one-hour surface O₃ to decrease by up to 12% with largest decreases in eastern China.  The potential impact of reducing SO2 and black carbon (BC) emissions by 80% on aerosol amounts was estimated via two sensitivity simulations. Reducing SO2 decreased surface PM2.5 concentrations in the Sichuan Basin and southern China by 5% and decreased ozone by up to 6 ppbv in the Sichuan Basin and Southern China. Reducing BC emissions decreased PM2.5 by 3% in eastern China and the Sichuan Basin but increased surface ozone by up to 4 ppbv in eastern China and the Sichuan Basin.  This study indicates that the benefits of reducing PM2.5 associated with reducing absorbing aerosols may be partially offset by increases in ozone at least for a scenario when NOx and VOC emissions are unchanged.  Additional simulations of the same period are currently in progress to evaluate the impact of the aerosol indirect effect on surface radiation and air quality.  Highlights from these simulations will also be shown.