The Contribution of Precipitation Recycling to North American Wet and Dry Precipitation Extremes

Over the course of a season, a location’s precipitation is comprised of moisture sourced from a diverse set of geographic regions. Seasonal extremes in precipitation may arise from changes in the contribution of one or several of these sources. Here, we use the Community Earth System Model with numerical water tracers to quantify the contribution of locally sourced, known as precipitation recycling, versus remotely sourced precipitation to seasonal wet and dry extremes across North America. The greatest impact of recycling on both wet and dry extremes is found in the Interior West of the United States where changes to recycling contribute as much as 25%–30% of drought deficit and pluvial surplus. Recycling contributions are smaller across the eastern U.S., generally less than 8%, highlighting the greater role of imported moisture for explaining hydroclimate extremes in these regions. Robust contributions of precipitation recycling to drought and pluvials across the Interior West are driven by consistent changes to local evaporation and the conversion of local evaporation to local precipitation during extreme hydroclimate conditions. The results are consistent with an energy-limited and water-limited evaporation framework and provide a new estimate of the role of local processes in shaping hydroclimate extremes.