Change in the uniformity of the temporal distribution of precipitation across the Mid-Atlantic region of the United States, 1950-2017

Recent research suggests that the characteristics of precipitation, particularly extremes and variability, are changing with a warming global climate. This study demonstrates a budding approach to analyzing the temporal uniformity of precipitation using daily data for the Mid-Atlantic region of the eastern United States over the period 1950 to 2017. The Gini coefficient (GC) assesses the equity of a distribution of an accumulated quantity across individual contributors. In this study, the GC characterizes the equity with which daily precipitation events contributed to seasonal and annual precipitation amounts through the study period. The Lorenz asymmetry coefficient (LAC) expresses the relative magnitude of precipitation events (heavy, light) that were primarily responsible for instances of inequity. Time series analysis of precipitation amount, wet-day frequency, wet-day GC values, and wet-day LAC values for each of 158 stations within the Mid-Atlantic region and for the region as a whole reveal ongoing change in the hydroclimate. Over the 68 yr study period, the region experienced increases in annual precipitation amount and wet-day frequency, while precipitation became less evenly distributed across precipitation events. The results suggest that extreme precipitation events are becoming more prevalent. Heavier and lighter events are increasing at the expense of moderate events.