21 January 2019

Projecting Changes in Societally Impactful Northeastern U.S. Snowstorms

Nor'easters are here to stay.

Science

While mean annual snowfall is projected to decrease over the northeastern United States by the end of the century, the vast majority of this is associated with a greatly reduced frequency of weak and moderate snowfall events. Large, crippling, nor'easters are forecast to occur with roughly the same frequency as today, even in a warmer climate. Therefore, while future winters may see less snowy days, systems producing massive regional impacts will not be correspondingly mitigated.

Impact

The paper describes a novel metric to quantify regional snowstorms from a societal impacts standpoint. Individual storms within a large climate ensemble are detected, providing a phenomenological, hazard-based analysis of wintertime extremes. This provides an important tool for societal, economic, and hydrological sectors, where rare, intense events play a disproportionately large role in significant harms.

Summary

This work first defines a metric with the capability to efficiently detect and track regional snowstorms in gridded weather and climate data. This allows for storm-level statistics to be extracted from climate datasets and these storms to be characterized by their impacts on society. Using the Community Earth System Model Large Ensemble (CESM LENS), it is found that snowstorms in the northeastern United States will decrease by the end of the century. However, this decrease is primarily constricted to less impactful snowstorms. Even with a warmer atmosphere and shorter snowfall season, larger storms are projected to occur with approximately the same frequency as in today's climate. This is due to the fact that future cyclones moving up the coast of the eastern United States will carry more moisture. Therefore, when atmospheric conditions align to support snow, storms will produce intense snowfall rates and accumulation totals.

Contact
Colin Zarzycki
National Center for Atmospheric Research
Publications
Zarzycki, C.  2018.  "Projecting Changes in Societally Impactful Northeastern U.S. Snowstorms."  Geophysical Research Letters 45(21): 12067-12075.  https://doi.org/10.1029/2018gl079820.