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Thermodynamic and Dynamic Contributions to Tropical Cyclone Precipitation Increases in Observations and Models

Presentation Date
Tuesday, December 14, 2021 at 1:20pm
Convention Center - New Orleans Theater C



Extreme precipitation is expected to increase with climate change at the Clausius-Clapeyron rate of approximately 7% per degree of warming; however, tropical cyclone (TC) precipitation may increase at a greater rate due to feedbacks between the storm dynamics and the thermodynamic increase in moisture. Previous studies simulate increasing TC intensities with warming sea surface temperatures (SSTs), which may push the precipitation increase above the Clausius-Clapeyron rate. TC outer size is another storm characteristic that may be impacted by SST and can influence precipitation amounts. This study breaks down TC precipitation increases with warming into thermodynamic and dynamic contributions using reanalysis (ERA5), observational datasets, and idealized global model simulations. The observations are a combination of precipitation estimates from the IMERG satellite and SST from NOAA’s OISST and Met Office’s HadISST datasets. The model results are from the Community Atmosphere Model (CAM) run in a state of radiative-convective equilibrium with globally-uniform SSTs varying between 295 and 305 K in 1 K increments. This SST range was chosen because it includes the SSTs most frequently observed under TCs in the real world. These idealized model simulations produce tens of thousands of TC precipitation snapshots, which allows an analysis of precipitation changes with a much larger sample size compared to observations. Differences in the TC precipitation composites and thermodynamic and dynamic contribution breakdowns between the models, reanalysis, and observations are discussed. While preliminary results depend on the precipitation metric that is used, they do suggest that thermodynamic changes contribute the most to TC precipitation increases but changes in storm intensity with SST are also important.

Funding Program Area(s)