Recent variability and trends and projected changes in precipitation in the southeastern United States: A focus on the Apalachicola-Chattahoochee-Flint River Basin

Changes in precipitation impacts water availability in river basins; therefore, it is important to perform detailed analyses of precipitation variables within regions to better understand drivers of precipitation variability. This study, which focuses on the Apalachicola-Chattahoochee-Flint River Basin in the southeastern United States, provides an analysis of precipitation variability during 1980–2021 and connects that information to circulation variables while also exploring the alignment between recent and projected precipitation changes. Data include daily precipitation totals from 33 stations, monthly values for circulation indices, and downscaled precipitation projections from climate models. Results show the pressure gradient across the southwestern North Atlantic Ocean and southeastern United States – which is a function of the strength and position of the Bermuda High – is strongly correlated with the precipitation variables and is an important control of precipitation variability in the basin. In contrast, most teleconnection indices are relatively weakly correlated with precipitation. The basin has generally been getting wetter, with summer having the largest increases in precipitation totals and precipitation days and thus large decreases in maximum consecutive dry days. Increases in heavy-precipitation variables are relatively small, with the largest increases in the northern portion of the basin. Precipitation is projected to increase in the next several decades compared to recent decades, with heavy precipitation expected to have the largest increase. Since the Bermuda High is the dominant driver of precipitation in the basin, more information is needed about specific changes to the Bermuda High in upcoming decades to produce better precipitation projections.