Exploring the spatiotemporal trends of extreme precipitation indices for the continental United States

Impacts of extreme precipitation call for additional attention to their trends and representation. Linear temporal trends in extreme precipitation indices (1981–2022) across the contiguous USA are identified using the 0.25°x0.25° European Centre for Medium-Range Weather Forecast (ECMWF) fifth-generation reanalysis (ERA5) and the Climate Hazards Group Infrared Precipitation with Station Data (CHIRPS). Although statistically significant increases in annual precipitation are limited in space, trends in extreme precipitation indices are more widespread. Annual frequency of days with ≥10 mm (R10) and ≥20 mm (R20) of precipitation showed a statistically significant increase in parts of the Ohio Valley and Northeast and decreased in the parts of the South, Southwest, and West, with broader R10-trending areas. Trends in the maximum five-day precipitation (Rx5day) and total precipitation exceeding the 95th percentile (R95P) show similar spatial patterns as R10 and R20. Trends in the annual maximum number of consecutive wet (CWD) and dry (CDD) days were significant only in isolated areas. CDD increased significantly in much of the Southwest and West. The study’s findings suggest that western regions of the country are experiencing more significant and widespread increase in aridity, while certain areas of the eastern regions are experiencing a trend of increased precipitation extremes.