Spatial and Temporal Variability in the Relationship between Water Vapor Transport and Associated Precipitation in the Eastern United States

Observed and projected changes in the precipitation regime of the eastern United States have been reported in numerous recent reports and studies. To improve understanding of these changes, this study investigates the variability in atmospheric moisture fluxes sourcing precipitation in this region. Water vapor fluxes were calculated as integrated vapor transport (IVT) from daily zonal and meridional vertically integrated vapor fluxes from ERA-Interim Reanalysis for 1979—2017. A machine learning self-organizing map methodology was employed to identify major patterns of atmospheric moisture transport, developing a climatology of water vapor fluxes for the eastern US. Precipitation characteristics for each of the water vapor fluxes were then analyzed using a PRISM gridded precipitation product at 4 km resolution from 1981-2017. Precipitation produced by many of the water vapor fluxes varied over this time period, with some water vapor fluxes producing more precipitation with increased frequency over these decades while other water vapor fluxes produced less frequent light precipitation. This cross-scalar approach linking broad-scale atmospheric moisture patterns to local-scale precipitation highlights the spatial variability in the precipitation received under each atmospheric moisture transport pattern while contextualizing local and regional precipitation patterns within a synoptic climatological framework. These relationships between water vapor fluxes and precipitation improve the understanding of precipitation variability in the eastern US vis-à-vis the Clausius-Claperyon relationship, situating researchers to better understand projected changes in the regional hydroclimatic regimes.