A 30-Year Climatology of Northeastern United States Atmospheric Rivers

Abstract Atmospheric rivers (ARs) are a frequently studied phenomenon along the west coast of the United States, where they are typically associated with the heaviest local flooding events and almost half of the annual precipitation totals. By contrast, ARs in the Northeastern United States have received considerably less attention. The purpose of this study is to utilize a unique visual inspection methodology to create a 30-year (1988-2017) climatology of ARs in the Northeast United States. Consistent with its formal definition, ARs are defined as corridors with integrated vapor transport (IVT) values greater than 250 kg m−1 s−1 over an area at least 2000 km long but less than 1000 km wide in association with an extratropical cyclone. Using MERRA2 reanalysis data, this AR definition is used to determine the frequency, duration, and spatial distribution of ARs across the Northeast United States. Approximately 100 ARs occur in the Northeast United States per year, with these ARs being quasi-uniformly distributed throughout the year. On average, Northeast United States ARs have a peak IVT magnitude between 750-999 kg m−1 s−1, last less than 48 h, and arrive in the region from the west to southwest. Average AR durations are longer in summer and shorter in winter. Further, ARs are typically associated with lower IVT in winter and higher IVT in summer. Spatially, ARs more frequently occur over the Atlantic Ocean coastline and adjacent Gulf Stream waters; however, the frequency with which large IVT values are associated with ARs is highest over interior New England.