Observed Changes in Extreme Precipitation Associated with United States tropical cyclones

Abstract Numerous recent tropical cyclones have caused extreme rainfall and flooding events in the CONUS. Climate change is contributing to heavier extreme rainfall around the world. Modeling studies have suggested that tropical cyclones may be particularly efficient engines for transferring the additional water vapor in the atmosphere into extreme rainfall. This paper develops a new indicator for climate change using the enhanced rainfall metric to evaluate how the frequency and/or intensity of extreme rainfall around tropical cyclones has changed. The enhanced rainfall metric relates the amount of rain from a storm over a given location to the 5-year return period rainfall in that location to determine the severity of the event. The annual area exposed to tropical cyclone-related 5-year rainfall events is increasing, which makes a compelling climate change indicator. Quantile regression illustrates that the distribution of tropical cyclone rainfall is also changing. For tropical storms, all quantiles are increasing. However, major hurricanes show large increases in their most extreme rainfall. This study does not attempt to make any detection claims (vs. natural variability) or attribution of the observed trends to anthropogenic forcing. However, the sensitivity of the results to natural variability in tropical cyclone frequency was somewhat constrained by comparing two decades from the previous active era (1951–1970) with two from the current era (2001–2020). This comparison also shows that both the mean and maximum rainfall associated with tropical cyclones is increasing over most areas of the eastern CONUS with the most significant increases from northern Alabama to the southern Appalachians.