Modeling Aerosol Direct and Indirect Effects in China

Atmospheric aerosols can affect climate directly via absorption and scattering and indirectly via serving as cloud condensation nuclei and changing formation and lifetime of clouds. Quantifying such effects, in particular, the indirect effect, has been identified as a top research priority by the Intergovernmental Panel on Climate Change (IPCC), the U.S. National Research Council, and Ministry of Science and Technology of China. These effects occur through a variety of atmospheric climate-chemistry-aerosol-cloud-radiation feedback processes. Accurately simulating these feedback processes and resultant effects requires the use of online-coupled meteorology-chemistry models; among which the Weather Research and Forecast Model with Chemistry (WRF/Chem) represents a state-of-the-science online model.

In this work, aerosol direct and indirect effects via various feedback mechanisms over China are studied using WRF/Chem. Model simulations are being conducted at a horizontal grid spacing of 36-km for January, April, July, August, and October, 2008 episode to quantify the magnitudes, spatial distributions, and seasonal variation of such effects. The feedbacks of aerosols to radiation, boundary layer meteorology, and cloud formation will be analyzed. The contribution of anthropogenic aerosols to aerosol total direct and indirect effects will be estimated. The effect of emission control on air quality and climate-chemistry-aerosol-cloud-radiation feedbacks during August 2008 Olympic games will be examined by comparing simulated aerosol direct and indirect effects for July and August. The important scientific and policy implications of aerosol effects and related feedbacks on climate change mitigation and air quality improvement will be discussed.