Future changes in the Frequency of Winter Snowstorms over North America.

Abstract:

This work explores the combined effects of future increases in winter temperatures and changes in the frequency and intensity of Extratropical Cyclones (ETCs) on snowfall and snow water equivalent (SWE) across North America. Future changes in the characteristics of snow over North America will have important socioeconomic implications as snow influences water supply, drought and wildfires, ecosystem habitats, recreation, flooding, and damages corresponding with hazardous snowstorms. This study uses a storm-relative approach by tracking individual ETCs and assessing future changes in storm intensity and storm precipitation at the individual storm scale. While past studies have primarily considered shifts in the mean or distribution of single climate variables (e.g. snowfall) this study investigates how anthropogenic climate change imprints onto the frequency, intensity, and spatial coverage of individual events. These individual events will have the largest effect on the environment, populations, and economies of North America. The goal of the work presented here is to answer the following questions:

1) How well do the CMIP6 models capture the characteristics of cold-season ETCs over North America and is storm-relative snowfall well represented within simulated ETCs?

3) In a warming climate, does storm-relative cold-season snowfall change in relationship to ETCs?

To answer these questions, we use TempestExtremes, an automated Lagrangian detection algorithm, to track cold-season (October-April) ETCs across North America in multiple global reanalyses and in the CMIP6 historical and future climate scenario simulations. ETCs have been tracked using sea level pressure deficits in gridded data and the precipitation associated with individual storms has been extracted using a simple storm-following approach.