You are here

Impacts of aerosols on precipitation

Event Type: 
Event Date: 
18 July 2017 - 8:00am
EOS Seminar Room - N2-01B-28
Chien Wang
About the speaker: 

Dr Chien Wang is a Senior Research Scientist of Atmospheric Chemistry in MIT’s Center for Global Change Science. He is also with MIT’s Joint Program on the Science and Policy of Global Change, Program in Atmospheres, Oceans and Climate (PAOC), and Department of Earth, Atmospheric, and Planetary Sciences (EAPS). Chien is one of the Principal Investigators of the Center of Environmental Sensing and Modeling (CENSAM) of the Singapore-MIT Alliance for Research and Technology (SMART).

Chien’s research interests include atmospheric aerosols and clouds, tropospheric chemical processes, and the roles of aerosol-cloud interaction in atmospheric chemistry, precipitation, and climate dynamics. He studies climate impacts of anthropogenic activities that alter atmospheric compositions or change the Earth’s surface properties or energy budget.

He has a degree in atmospheric physics from Peking University, China, a Ph.D. in atmospheric sciences at the State University of New York at Albany, and previously worked as a postdoc at Scripps Institute of Oceanography, UCSD.

About the event: 

Aerosol remains one of the most uncertain factors in climate projection. Aerosol can affect the radiative balance of the climate system by directly scattering or absorbing sunlight, or by acting as cloud condensation nuclei and ice nuclei and thus modify the optical properties as well as lifetimes of clouds. It has been known for long that such effects contribute to the variation of Earth’s surface temperature. On the other hand, aerosol can influence precipitation by either modifying cloud microphysical processes through aerosol activation, or by modifying local thermodynamical profile, facilitating an on-site impact on clouds overlapping with the aerosol population. In addition, recent studies have also suggested that the direct and indirect radiative effects of aerosols can perturb the large-scale circulation and cause significant changes in cloud cover and precipitation in places often distant from aerosol-laden regions, i.e., facilitate a remote impact. Understanding and quantifying the impact of aerosol on precipitation is a more challenging task than doing so on temperature because the former impact involves many sophisticated feedbacks that are still difficult to measure or model. Recent progress to include interactive aerosol features in many climate or Earth system models besides process models has made it possible to study aerosol-cloud-precipitation mechanism through long climate integrations, by considering the inhomogeneous distribution of aerosol forcing and feedback, or by combining with or separating from other anthropogenic forcers. For instance, recent results of models with above-mentioned improvements suggest that aerosol has played a dominant role over greenhouse gases in causing pattern changes of many precipitation systems in past decades.  I will use research findings to discuss the current understanding alongside major challenges of both on-site and remote impacts of aerosol on precipitation.