Patterns of Water Vapor Transport in the Eastern United States

Abstract

AbstractThis study presents a climatology of water vapor fluxes for the eastern United States and adjacent Atlantic with particular focus on the Northeast. Pathways of moisture transport comprising this climatology were discerned using a self-organizing map methodology ingesting daily integrated vapor transport data from ECMWF ERA-Interim Reanalysis from 1979 to 2017 at a 2.5° × 2.5° spatial resolution. Sixteen spatially distinct moisture transport patterns capture the variety of water vapor transport in the region. The climatology of water vapor transport is precisely and comprehensively defined via synthesis of spatial and temporal characteristics of the fluxes. Each flux has a distinct seasonality and frequency. The fluxes containing the highest amounts of moisture transport occur less frequently than those with less moisture transport. Because the patterns showing less moisture transport are prevalent, they are major contributors to the manner in which water vapor is moved through the eastern United States. The spatial confinement of fluxes is inversely related to persistence, with strong, narrow bands of enhanced moisture transport most often moving through the region on daily time scales. Many moisture fluxes meet a threshold-based definition of atmospheric rivers, with the diversity in trajectories and moisture sources indicating that a variety of mechanisms develop these enhanced moisture transport conditions. Temporal variability in the monthly frequencies of several of the fluxes in this study aligns with changes in the regional precipitation regime, demonstrating that this water vapor flux climatology provides a precise moisture-delivery framework from which changes in precipitation can be investigated.