Maya Robinson and Gary M. Lackmann
Department of Marine, Earth, and Atmospheric Sciences
North Carolina State University
Global climate change will undoubtedly have large impacts on the atmospheric patterns we are accustomed to. Extensive research has been done across many fields to determine what those impacts will look like, but there has been little focus on how climate change will affect snowfall and snowfall rates. Previous studies have hypothesized that increased water vapor content will lead to an increase in maximum rainfall rates, but it is not clear how future snowfall rates will respond to warming. On one hand, less snow is expected due to warming, but if precipitation rates increase, then peak snowfall rates could increase. Using a set of twenty high resolution model simulations (ten for the current climate, and ten corresponding to the IPCC RPC8.5 scenario), this research investigates the changes in snowfall and rainfall during the winter season in the eastern United States due to climate change. While this study only focuses on the eastern half of the United States, it gives some insight into the changes in winter precipitation that people in the area may expect from climate change, so they can begin to consider mitigation approaches for those changes. The model was run for ten individual current years using analyzed SST fields. For each year, the model was run again but with sea surface temperatures adjusted to indicate 100 years of climate change derived from GCM output, applied as a “delta” to the analyzed SST fields from the present day simulations (akin to pseudo-global warming methods). The data analyzed includes fourteen years of snowfall data and twenty years of rainfall data from November 1st to March 31st, bounded from 23 to 50 N and -100 to -60 W. To determine the changes in snowfall and rainfall with climate change, difference plots of the season total and the maximum 6 hourly accumulation were examined. By taking the difference in the future and current years, the changes are clearly defined, with positive values indicating an increase in the respective precipitation type, and negative values indicating a decrease.
As expected, the season total snowfall plot shows a clear decrease across much of the study area, with a few areas in the midwestern United States and southern parts of Canada exhibiting an increase. The maximum 6 hourly snowfall accumulation shows a decrease across much of the southern and northeastern United States, and an increase across much of the Midwest and southern parts of Canada. The season total rainfall plot shows an increase along the eastern seaboard and across the midwest. There is an area extending from the northern portion of Georgia to Texas, along and below 35 N, that primarily sees a decrease in rainfall. The maximum 6 hourly rainfall accumulation shows an increase across the majority of the study area, with the majority of the greatest increases across the south and only a few small areas that show a decrease.
There are additional questions that stem from this research as well, such as possible changes in the seasonality of snow and rain climatologies in various parts of North America. Despite the fact that the seasonal snowfall totals decrease, does the average snowfall rate increase due to increased water vapor content? Are there fewer snow events, with more snowfall per event? We will explore these questions and others, using this novel set of global, high-resolution model simulations.