Atmospheric rivers over eastern US affected by Pacific/North America pattern

Atmospheric rivers can drive weather in the Eastern United States. Credit: NOAA

There is a growing awareness that atmospheric river (AR) activities are responsible for a wide range of environmental and socioeconomic impacts on the West coast of the U.S. The related heavy rainfall, snowfall, and associated floods, especially during winter, have been a focus of many previous studies. This research investigates the impact of AR on the Eastern U.S. (EUS).

ARs in the EUS remain relatively understudied, despite their frequent occurrence and substantial contribution to heavy precipitation and high-impact weather events. The authors examined wintertime AR frequency over the EUS during the past four decades, using multiple observations and a state-of-art high-resolution climate model (AM4) developed at GFDL. These results show that there is a significant increase in AR frequency over EUS during this period.

The increased AR frequency is principally related to the recent changes in the Pacific/North America (PNA) teleconnection pattern, accompanied by a poleward shift of the midlatitude jet stream. Model simulations, using GFDL’s AM4, well capture the observed mean AR and circulation features but fail to simulate their respective trends. Nonetheless, their linkages with the PNA pattern are verified across different realizations, highlighting the critical role of the PNA pattern in regulating the AR variability.