Extreme precipitation can produce severe flooding, causing significant hydrologic and socioeconomic impacts. However, extreme precipitation can also deposit a substantial amount of water in the soils that can enhance subsequent evapotranspiration. The later process representing a long-term hydroclimate impact associated with extreme precipitation is largely unknown. In this study, we aim to understand this process occurring with 24 mesoscale convective systems (MCSs) that caused severe flooding over the Southern Great Plains in May 2015 by using a new land-atmosphere coupled water tracer tool in WRF. This new tool allows us to “tag” MCS precipitation as tracer moisture and track its contribution to different hydrologic components, including as it leaves the soil through evapotranspiration and becomes available for precipitation at a later time.

During May, our simulation reveals that ~19% of the “tagged” MCS precipitation becomes runoff contributing to flooding and ~28% becomes evapotranspiration contributing to the “fast recycling”, while ~52% is stored in the soil by the end of May. In June and July, the tracers from MCS precipitation in May stored in the soil start to decay exponentially through evapotranspiration to become atmospheric moisture. Two interesting findings are concluded during June and July: (1) while the e-folding time for the decaying tracer soil moisture is ~5-25 days, depletion of tracer soil moisture is accelerated when new precipitation events occur that wet the soil and enhance evaporation, (2) tracer moisture in the atmosphere can influence the moisture and precipitation 500-700km downstream of the tracer release region. Our study shows how the land-atmosphere coupled tracer tool may be used to understand the hydroclimate impact of extreme precipitation beyond the timescale of individual storm events.