PNNL

Abstract

Extreme precipitation events often produce severe flooding and pose significant threats to our society. However, their subseasonal impacts on the terrestrial and atmospheric systems are not well understood. Here, we use a new land-atmosphere coupled water tracer tool embedded in WRF to “tag” precipitation produced by a series of extreme mesoscale convective systems (MCSs) in May 2015 over the Southern Great Plains to reveal their contributions to different terrestrial water storages and moisture recycling during May-July. During May, we find that precipitation from earlier MCSs can contribute to 20-50% of total evapotranspiration (ET) in later May and contribute to ~10% of local precipitation for later MCSs. After May, the water “tagged” to preceding May MCS events has the most active contribution to moisture recycling during the first 5 days in June, but this contribution diminishes quickly afterwards. Both periods indicate a quick turnover of “tagged” precipitation, which may be representative in the Southern Great Plains region. The quick turnover is closely associated with the direct evaporation from the soil surface due to the predominant shrubland and grassland coverage over this region. Over some forested areas, however, the tracer-ET flux is dominated by transpiration that stably supplies a small fraction (