A Comparison of the Rates of Change Associated With Hourly and 24-Hour Precipitation Extremes Across the Eastern United States

Abstract

This study investigates changes in extreme precipitation across the eastern United States using hourly data from 127 stations collected between 1950 and 2023. Median hourly precipitation exceedances have become more frequent at nearly all stations, with more pronounced increases observed for hourly extremes compared to 24-hr extremes. However, when examining more extreme thresholds (e.g., 90th percentile), 24-hr precipitation events show greater relative increases in frequency compared to hourly events. For the most extreme events, precipitation amounts exceeding a 50% annual recurrence probability based on partial duration series analysis extremes reveal that longer-duration (24-hr) extreme precipitation events have increased more consistently and significantly than shorter-duration (hourly) events. Changes in the distribution parameters of the Gamma and Generalized Extreme Value distributions indicate a shift toward more frequent but smaller precipitation events in recent decades, accompanied by an increase in overall event intensity. These results have important implications for flood risk management and infrastructure design, underscoring the need for region-specific adaptation strategies in response to the evolving nature of extreme precipitation under a changing climate.