报告题目：How Aerosols Modify Cloud Dynamics, Microphysics and Precipitation

报告人：Jiwen Fan，Ph.D., Scientist，Climate Physics, Pacific Northwest National Laboratory, Richland, WA99352
报告时间：2010年9月28日上午10点
报告地点：40号楼902
 

Abstract

It is widely recognized that aerosol-cloud interaction plays an important role in climate. The aerosol indirect effects refer to the influence of aerosol on cloud microphysical processes and are highly uncertain currently. For deep convective clouds (DCCs), aerosol-DCC interactions are especially complex and continue to be puzzling us as more ‘aerosol effects’ unfold, and systematic assessment of such effects is lacking. Aerosols can significantly change cloud microphysical process by acting as both cloud condensation nuclei (CCN) and ice nuclei (IN). The feedback to cloud dynamics may dramatically change convective strength, cloud morphology, radiation and precipitation.  We employ a state-of-art cloud-resolving model (CRM) coupled with spectral-bin cloud microphysics (SBM) to systematically examine how aerosols change cloud microphysical processes and the feedbacks to cloud dynamics, and then how precipitation is changed with the combination of the microphysical and dynamic effects. We find a dominant role of vertical wind shear in regulating aerosol effects on isolated DCCs, i.e., vertical wind shear qualitatively determines whether aerosols suppress or enhance convective strength. By examining the effects of aerosols by acting as CCN and IN on cloud anvil macrophysical and microphysical properties, we find that cloud microphysical changes induced by CCN/IN play a very important role in determining cloud anvil area, whether convection is enhanced or suppressed. CCN effects on anvil microphysical properties, anvil size and lifetime are much more evident relative to IN.  We also show an important role of CCN in the lower-troposphere in modifying convection and the upper-level cloud properties. Our process studies considering the full interactions between aerosols, cloud microphysics, and dynamics with high resolution CRM simulations help understand how pollution affects clouds, precipitation and climate, and provide physical explanations for many observational phenomena. Regional climate studies are also conducted to look into the contribution of aerosols to the changes of climate and precipitation in the Southeast of China.