Extreme Snow Events along the Coast of the Northeast United States: Potential Changes due to Global Warming

Winter extreme snowstorm events along the coast of the northeast United States have significant impacts on social and economic activities, and their potential changes under global warming are of great concern. Here, we adopted the pseudo-global warming approach to investigate the responses of 93 events identified in our previous observational analysis. The study was conducted by contrasting two sets of WRF simulations for each event: the first set driven by the ERA-Interim reanalysis and the second set by that data superimposed with mean-climate changes simulated from HiRAM historical (1980-2004) and future (2075-99; RCP8.5) runs. Results reveal that the warming together with increased moisture tends to decrease the snowfall along the coast but increase the rainfall throughout the region. For example, the number of events having daily snow water equivalent larger than 10 mm day(-1) at Boston, Massachusetts; New York City, New York; Philadelphia, Pennsylvania; and Washington, D.C., is decreased by 47%, 46%, 30%, and 33%, respectively. The compensating changes in snowfall and rainfall lead to a total-precipitation increase in the three more-southern cities but a decrease in Boston. In addition, the southwestward shift of regional precipitation distribution is coherent with the enhancement (reduction) of upward vertical motion in the south (north) and the movement of cyclone centers (westward in 58% of events and southward in 72%). Finally, perhaps more adversely, because of the northward retreat of the 0 degrees C line and the expansion of the near-freezing zone, the number of events with mixed rain and snow and freezing precipitation in the north (especially the inland area) is increased.

Automated summary

This study used a pseudo-global warming approach to investigate the responses of 93 winter extreme snowstorm events along the coast of the northeast United States under global warming conditions. Results showed that warming and increased moisture tend to decrease snowfall along the coast but increase rainfall throughout the region, with compensating changes in total precipitation in different cities. Additionally, the study found a southwestward shift in regional precipitation distribution and an increase in events with mixed rain and snow due to the northward retreat of the 0 degrees C line and expansion of the near-freezing zone.