Variability of moisture recycling using a precipitationshed framework

Moisture recycling, whereby evaporation from Earth's surface flows through the atmosphere and falls out as precipitation on land downwind, is increasingly being acknowledged as an important feature of the global Earth system. There is still substantial uncertainty of how climatic variability can cause influence large scale moisture recycling patterns. Understanding the historical variability of moisture recycling is critical for quantifying and determining the relative importance of drivers such as land use change or increasing greenhouse gases. This research explores this topic by quantifying the variability of moisture recycling for several key regions globally, using the precipitationshed as the spatial unit of analysis. We employ the Water Accounting Model (WAM 2-layer), a numerical water transport model, to track how moisture flows through the atmosphere. Using two reanalysis datasets, variations in moisture recycling relationships are identified. The results suggest that variability is relatively low during the thirty years of analysis, and that most deviations from the mean for the studied regions are driven by changes in terrestrial evaporation. Given that there is low observed variability in the sources of moisture for specific moisture sink regions we conclude that the relatively stable source and sink relationships lead to upwind and downwind social dynamics similar to those in surface watersheds.