Collaborative Research: Contrasting the Effects of Aerosols on Marine Boundary Layer (MBL) Cloud-precipitation Properties and Processes in Boreal and Austral Mid-latitude Regions

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The project is to investigate formation of marine-boundary-layer clouds, which are clouds that are directly influenced by the ocean. Particularly, how tiny suspended particles or aerosols contribute to clouds and how clouds interact with aerosols. Aerosols are generated from atmospheric, land, and oceanic processes such as urban/industrial activity, dust storms, burning vegetation, biological activity, sea spray, wind currents, and volcanoes. Certain aerosol types can initiate marine-boundary-layer cloud development more easily than others. This adds to the complexity and uncertainty of marine-boundary-layer cloud impacts on weather variations. Marine-boundary-layer clouds have significant climatological effects on the hydrological cycle and the Earth’s radiation balance. For example, varying distributions of marine-boundary-layer clouds around the globe contribute to areas of deficits and surpluses in solar energy and rainfall. Many studies have been conducted on aerosol-cloud interactions in the Northern Hemisphere where most of the global population and landmasses are located. Not much is known over the vast area of remote land and oceanic regions in the Southern Hemisphere. This study will investigate differences and similarities of aerosol-cloud interactions between the Northern and Southern Hemispheres by analyzing recent field observations and utilizing numerical model simulations. The project involves undergraduate and graduate students to participate in the research project and train them to be the next generation of scientists.This study employs long-term ground-based observations and remote sensing retrievals from a dedicated observation site in the Eastern North Atlantic Ocean and aircraft in situ measurements from two intensive field campaigns in 2018: 1) the Aerosol and Cloud Experiments in the Eastern North Atlantic (ACE-ENA), and 2) the Southern Ocean Clouds, Radiation, Aerosol Transport Experimental Study (SOCRATES). The research team utilizes a synergistic measurement/modeling approach in conjunction with meteorological patterns to compare the characteristics of marine-boundary-layer aerosol, cloud, and drizzle properties over the two hemispheres through answering three scientific questions. Those are: 1) what are the relative roles of surface cloud condensation nuclei and updrafts in aerosol-cloud interactions over the marine boundary layer and warm rain processes? 2) what are the characteristics of marine-boundary-layer aerosol, cloud and drizzle properties and their interactions during two field campaigns? 3) what are the characteristics of marine-boundary-layer aerosol, cloud, and drizzle properties, their interactions over the Southern Ocean, and their similarities and differences compared with those in the Eastern North Atlantic Ocean? Comparisons of precipitation processes and aerosol-cloud interactions at the two sites with significantly different environmental conditions will shed light on the controlling factors in aerosol-cloud interactions and eventually lead to a generalized parameterization for aerosol-cloud interactions applicable for the global climate models.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.