An Exploration of Extreme Precipitation from Tropical Cyclones over the Eastern United States in Variable-Resolution CAM

Thursday, December 12, 2019 - 13:40
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Tropical cyclones (TCs) create dangerous conditions for residents of the U.S. East and Gulf Coasts through different combinations of hazards: strong winds, storm surge, extreme rainfall, and subsequent flooding. While rainfall from TCs contributes a relatively small percentage to the total annual precipitation in the U.S., TCs can account for over 40% of extreme precipitation events in one year at some coastal locations; therefore it is important that these locations are prepared for heavy rainfall that TCs can produce over just a few days. This work explores the representation of TC-induced precipitation over the eastern U.S. in three variable-resolution versions of the Community Atmosphere Model (CAM) that have high-resolution (~28 km) domains over different extents of the North Atlantic basin: just over the western North Atlantic (WAT), over the whole North Atlantic (REF), and over the whole North Atlantic and northern Africa (EXT). To calculate TC-related precipitation in the models, the updated TempestExtremes algorithm is applied, which tracks TCs, estimates their sizes based on their lower-level wind fields, and extracts precipitation associated with the storms based on their sizes. Precipitation metrics, such as annual mean precipitation and Rx5day (annual maximum 5-day accumulated precipitation), from these different model grids are compared and evaluated against observations from the Tropical Rainfall Measuring Mission (TRMM) satellite and the Climate Prediction Center’s gauge-based analysis of daily precipitation. Additionally these results are compared to a model run performed with the REF grid under a future warming scenario (RCP8.5) to see how TC-induced precipitation may change over the eastern U.S. in the future.

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