Regional and global climate response to aerosol and GHG forcings
We employ the state-of-the-art Earth system models and regional climate models (e.g. MPAS, CESM, MMF, WRF-Chem) as well as long-term climate records (satellite products, reanalysis data) to understand the physical pathways for aerosol and GHG effects on regional and global climate and project their future responses. Foci are put on the climate extremes and large-scale and mesoscale interactions.
Anthropogenic Aerosol Impacts on Sea Ice
We employed the fully coupled CESM climate model to explore effects of man-made aerosols on historical and future variations of the Arctic sea ice in comparison with the GHG forcing. Aerosol-induced cloud forcing and subsequent feedback processes are found critical. In the next few decades, the projected alleviation of particulate pollution in the Northern Hemisphere can contribute up to 20% of the total Arctic sea ice loss and 0.78C surface warming over the Arctic.
Air Cleaning Suppressed Winter Extremes
Anthropogenic aerosol emissions decreased over North America and Europe but increased over Asia since the 1970s. We revealed that this aerosol forcing caused jet stream winds to shift poleward over the Atlantic, decreasing planetary wave activity and partially inhibiting extreme winter weather over northern Eurasia. It stresses the importance of anthropogenic aerosols and their spatiotemporal variability in assessing the drivers of extreme weather in historical and future climate.
Pollution and Climate Change on Crops
We developed a robust crop yield prediction model and reveals a critical role of particulate pollution in determining annual crop yields. The present study demonstrates the co-benefit of the recent air pollution control policy from agriculture and food perspectives. However, this benefit will eventually be diminished after the air pollution becomes alleviated in the full scale, while persisting or even exacerbated global warming will pose larger threat on the future food security.
Asian Air Pollution Boost Pacific Storms
Increasing levels of air pollutants in Asia have recently drawn considerable attention, but the effects of Asian pollution outflows on regional climate and global atmospheric circulation remain to be quantified. Using multiscale models, we demonstrated that aerosol particles during the long-range transport of the Asian pollution seed convective clouds over the Northwest Pacific, energize the winter storms by releasing additional latent heat, and increase precipitation and poleward heat transport. Our work provides for the first time a global multiscale perspective of the climatic effects of pollution outflows from Asia.
Attribution of Extreme Precipitation in China
To reconcile the influence of aerosols and greenhouse gases on precipitation extremes, we implemented an in-situ diagnostics of precipitation probability distribution function in CAM5. A series of model simulations suggested aerosols primarily account for the light precipitation suppression in Eastern China. In contrast, greenhouse gas effects mainly enhance tropical precipitation extremes via dynamical pathways.
Black Carbon Radiative Forcing
We leveraged smoke chamber experiments in Beijing and Houston to constrain black carbon aging parameterizations in CAM5-MAM4 . The calibrated model shows that coating by other types of aerosols results in net enhancement in BC radiative forcing in spite of a reduction in BC lifetime. Our results suggest that accurate simulations of BC aging processes as well as other coating species are equally important in reducing the uncertainty of BC forcing estimation.
Dust Effects on Hurricanes
NCAR CESM model simulations were employed to study impacts of Saharan dust on the radiative budget, hydrological cycle, and large-scale environments relevant to tropical cyclone activity over the Atlantic. We found Saharan dust particles mainly interfere with solar radiation, impose temperature inversion, and generally suppress hurricane formation. Distinctive dust impacts on TC genesis and intensification regions were also reported.