Atmospheric River Clusters and Their Relationship to Cool Season Precipitation in the Northeastern United States

Atmospheric Rivers (ARs) are long, narrow corridors of enhanced vertically integrated vapor transport (IVT) with values generally above 250 kg m^-1s^-1 that are ahead of a cold front of an extratropical cyclone. ARs are more commonly studied on the West Coast of the United States, mainly due to the intense rainfall and flooding that contribute to their water supply. Given the lesser amount of research on ARs in the northeastern (NE) United States, this study examines the characteristics of AR clusters and their relation to cool season precipitation. For this study, an AR cluster was defined as (1) two or more simultaneous ARs, or (2) consecutive ARs with fewer than six hours between them in the NE region. Concurrent ARs can be more impactful given back to back rain events often cause more damage due to precipitation and flooding.

This study utilized a 30-year (1988-2017) AR climatology dataset from Kaminski et al. 2023 to analyze the intensity, duration, and frequency of AR clusters. Data analyses of ERA5 hourly data at eight stations across the NE, was used to narrow down the domain and observe trends for AR clusters in the cool season (November-April). Generally, AR clusters in the NE were found to be less frequent in the cool season, especially for further north locations. The cool season also featured AR clusters with lower IVT values, shorter durations, and fewer ARs within a cluster. Cool season AR clusters that had higher IVT values appear to produce more precipitation at both coastal and inland locations. At all locations in the NE region, more than 95% of AR clusters accounted for any amount of precipitation, and ~10% resulted in more than four inches of precipitation.