Impact of Surface-Cloud Coupling on Aerosol-Radiation- Cloud-Interactions for Boundary-layer Clouds over Land and Oceans

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The project seeks funding to investigate impacts of heating from the earth’s surface in transporting tiny particles (also called aerosols) and water vapor in the atmosphere upward to form clouds and precipitation as well as how aerosols and clouds affect the surface heating by blocking sunlight or the surface cooling by blocking the surface heat release---the process is called radiation. Aerosols are found mostly in the air layer of about 1 mile above the earth surface, which is also called the planetary boundary layer (PBL). Meteorology and the atmospheric environment in the PBL are of utmost importance to our lives. Interactions between aerosols/clouds and the earth’s surface are among the most uncertain factors in weather forecasting and climate studies. This project aims to improve understanding of some fundamental processes governing the interactions over both land and oceans. By examining the development of boundary-layer clouds and aerosol transport in the context of the surface-cloud coupling, this project will help advance our understanding of extreme weather, climate change, and air pollution, which are critical to the society. The research project will train young scientists to become the future generation of scientists and educators to understand and resolve problems facing weather forecasts.The overarching question of the proposed study is how aerosol-radiation interactions (ARI) and aerosol-cloud interactions (ACI) are affected by the coupling between clouds and the surface or the PBL for both continental and marine clouds. Because the coupling between clouds and the surface is expected to play an important role in regulating ARI and ACI, the project will sort out the boundary-layer processes dictated by the cloud-PBL-surface coupling. The study will test the hypotheses: (1) absorbing aerosols inhibit heat fluxes and the entrainment process of the PBL, suppressing convection initiation, and the development of continental cumulus clouds; (2) the fraction of surface cloud condensation nuclei reaching the marine cloud layer is lower under the decoupled condition, leading to markedly weaker ACI with weakened impacts on precipitation, whereas the opposite is the case for the coupled condition. Using comprehensive field observations, this project will investigate the impacts of ARI and ACI on the vertical distribution of heat fluxes, entrainment, and convection initiation for different surface-cloud coupling states. The project will also explore how the decoupling between clouds and the surface regulates aerosol vertical transport and how cloud micro- and macro-physical properties respond to the coupling state. These tasks will also help quantify the magnitudes of both individual and joint effects of ACI and ARI.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.