USA continental scale intensification of sub-daily precipitation intensities and erosivity

Evidence is building that precipitation is intensifying more rapidly over short time scales (up to a few hours) which could potentially increase flash flooding and soil erosion. However, the paucity of sub-daily precipitation observations has limited the number of studies investigating temporal trends to analysis using a few isolated rain gauges or to global and regional climate models. The United States Department of Agriculture (USDA)-Agriculture Research Service (ARS) Long-Term Agroecosystem Research (LTAR) Experimental Watershed network has systematically measured and archived sub-daily precipitation since the mid-twentieth century and its database represents a unique opportunity to evaluate temporal changes across different hydro-climatic environments. The goals of this study are: 1) to identify temporal trends in sub-daily precipitation intensities across different climatic regions for the period 1970-2013; 2) to evaluate if reported increases in rainfall intensities at the daily and hourly time scales are also observed at sub-hourly durations and; 3) to quantify the impacts of more intense precipitation on agricultural lands as measured by changes in soil erosivity. Our results show positive increases in precipitation intensities in the Northeast, Midwest, and Southwest regions at sub-daily scales ranging from 10 minutes to daily. In the most recent years (1993-2013), changes in precipitation intensities are more evident for the most intense events (events that occur, on average, once a year), compared to the earlier (1970-1992) period.