CAREER: Assessing Responses of Precipitation Extremes to Anthropogenic Emission Changes

Climate change, water resources, and human activities are coherently interconnected. Increased temperature due to greenhouse gases likely exacerbates the severity, frequency, and duration of hydrological extremes, such as droughts, flooding, and convective storms. Moreover, atmospheric aerosols from various sources also regulate precipitation intensity and efficiency via interactions with convective clouds and large-scale circulations, while those effects have not yet been fully accounted for in the present climate models. The overachieving scientific objective of this project is to advance the process-level understanding of anthropogenic aerosol on precipitation extremes. A series of critical science questions will be addressed in the project: to what extent extreme precipitation is sensitive to cloud and aerosol physics in a new-generation global weather/climate model; whether local precipitation extremes are linked to local and remote aerosol variations; what type of aerosol effect exerts larger impacts on convective precipitation. Results from the project will provide scientific evidence for policymakers to frame effective actions to address the potential flooding and drought issues in the future climate. This five-year project plans to first improve the extreme precipitation simulation by enhancing the representations of aerosol and cloud microphysics in a fully compressible non-hydrostatic global climate model with regional refinement capability, Model for Prediction Across Scales (MPAS), to convection-permitting scale. The complex impacts of anthropogenic aerosols on cloud and precipitation will be untangled under this modeling framework. The aerosol-aware MPAS will be evaluated against a suite of available ground-based and spaceborne observations. It will be further employed to assess the responses of crucial weather systems that regulate the variability of the water supply and the incidence of extreme precipitation events over East and South Asia as well as the western US, such as the Asian summer monsoons, the mid-latitude storms, and Atmospheric Rivers. The program will also train students through project-based learning by integrating extreme weather and air pollution research into graduate/undergraduate curricula. Outreach activities of the program will directly engage high school students in the research program and raise environmental and climate awareness among students and the public via student mentoring programs and a summer workshop. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.