The Association between Atmospheric Rivers and Extreme Precipitation over the Eastern United States

Atmospheric Rivers (ARs), or long narrow channels of elevated water vapor transport often associated with extratropical cyclones in the midlatitudes, have been identified as a prominent meteorological mechanism for extreme precipitation over the western United States (US). Here an AR detection algorithm is applied to global reanalysis from the Modern-Era Retrospective Analysis for Research and Applications, version 2 to investigate the link between ARs and precipitation extremes across the eastern US. AR detection is based on an objective identification algorithm involving an integrated water vapor transport magnitude thresholding variable and geometry requirements to account for length, width, and shape orientation criteria. Precipitation extremes are identified based on three-day precipitation totals exceeding the 95^th percentile at each grid point. Results show that a substantial proportion of extreme precipitation days are associated with ARs over parts of the eastern US across the seasonal cycle. However, a considerable proportion of precipitation extremes are not associated with ARs, suggesting the presence of other key driving mechanisms necessitating further consideration. Regional patterns of AR-driven precipitation suggest more dynamic and complex synoptically driven transport mechanisms compared to West Coast orographically enhanced precipitation extremes. Future applications of this work include assessing observational uncertainty associated with AR and extreme precipitation climatology and evaluating climate model skill at realistically simulating the seasonality and frequency of AR-driven heavy precipitation across the eastern US.