Precipitation Recycling Variability and Ecoclimatological Stability—A Study Using NARR Data. Part I: Central U.S. Plains Ecoregion

Abstract

Precipitation recycling is one of the key mechanisms linking the land surface and atmospheric dynamics. This work explores the physical mechanisms that modulate precipitation recycling variability at the daily-to-intraseasonal time scales in the central U.S. plains ecoregion using a set of land?atmosphere variables derived from the North American Regional Reanalysis dataset. Recycling estimates are performed using the Dynamic Recycling Model, which allows for analysis at shorter time scales than the previous bulk recycling models. In the central U.S. plains ecoregion local evapotranspiration only becomes an important contributor to precipitation when moisture of advective origin, the largest contributor to precipitation, diminishes. Consequently, the recycling ratio is negatively correlated to precipitation. The dominant mechanism is a negative feedback, which ensures that, even when precipitation is low, evapotranspiration continues to feed moisture into the overlying atmosphere and contribute to rainfall. Consequently, in the central U.S. plains, precipitation recycling acts as a mechanism for ecoclimatological stability through local negative feedbacks. Additionally, the zonal and meridional winds and moisture fluxes were also found to be important drivers of recycling variability. As winds decrease, the air has more time to traverse the region and capture moisture of evaporative origin. Evapotranspiration variability is not an important driver for recycling ratio variability in the central U.S. plains. Only during the extremely dry 1988 summer drought, when soil moisture storage was depleted, did the recycling ratio variability closely follow evapotranspiration.