Local moisture recycling across the globe

Abstract

Changes in evaporation over land affect terrestrial precipitation via atmospheric moisture recycling and consequently freshwater availability. Although global moisture recycling at regional and continental scales are relatively well understood, the patterns and drivers of local moisture recycling remain unknown. For the first time, we calculate the local moisture recycling ratio (LMR), defined as the fraction of evaporated moisture that rains out within approximately 50 km from its source, and identify its drivers over land globally. We derive seasonal and annual LMR from multi-year (2008–2017) monthly averaged atmospheric moisture connections at a scale of 0.5° obtained from a Lagrangian atmospheric moisture tracking model. We find that, annually, on average 1.6 % of evaporated moisture returns as rainfall locally, but with large temporal and spatial variability, where LMR peaks in summer and over wet and mountainous regions. We identify wetness, orography, latitude, and convective available potential energy as drivers of LMR, indicating a crucial role for convection. Our results can be used to study impacts of evaporation changes on local precipitation, with widespread implications for, for example, regreening and water management.