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Department of Environmental Studies and Sciences

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New Publication by Hari Mix

Hari Mix recently published two new papers with SCU alumnus Sean Reilly investigating atmospheric rivers

Hari Mix recently published two papers on the science of atmospheric rivers. Atmospheric rivers are long, narrow bands of extremely high moisture transport, responsible for half of California’s annual water budget and nearly all of its major flooding events. The first paper, published in Atmospheric Chemistry and Physics, examined ice nucleating particles (INPs), the small pieces of mineral dust, sea spray and bacteria on which ice crystals initially form and seed rain clouds. The team focused on INPs active at warm temperatures as they promote precipitation efficiency. One of the interesting new findings was that local bacteria greatly enhanced cloud ice formation, suggesting a “bioprecipitation feedback” where rainfall lofts bacteria from plants, thereby increasing future precipitation. The second, published in a special issue of Atmosphere on atmospheric rivers, addressed an ongoing debate surrounding the evolution of precipitation in frontal systems. By measuring simultaneous time series of the oxygen and hydrogen isotope composition of precipitation and water vapor, Mix and his colleagues determined that at some points of the storm, rainout of atmospheric moisture dominated the system, whereas in others, post-condensation processes such as below-cloud evaporation of raindrops played a significant role. ESS alum Sean Reilly was a coauthor on both papers. The studies were supported by a National Science Foundation grant to Mix.