Rain-on-Snow Research

    • Accurately establish and quantify climate trends related to extreme weather events occurring on the summit of Mount Washington for the period of September 1989 through May of 2020.
    • Investigate the changing seasonality around the winter on Mount Washington to determine if winters are warming and if this is impacting the summit snowpack as well as shifting the seasonality.

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Motivation and History

Warming New England winters can impact the type of precipitation across the region as well as the quality of the snowpack. The season that is experiencing the greatest warming across New England is the winter with New Hampshire winter temperatures increasing on average of 2.5 °C on a decadal scale between 1900 and 2020 (Young and Young 2021). A significant consequence of climate warming is the increase of rain on snow (ROS) events (Rennert et al. 2009). Periods of winter warming with near surface temperatures above 0 °C are becoming more frequent (Sobota, Weckwerth, and Grajewski 2020; Peeters et al. 2019; Graham et al. 2017). These events are typically characterized as exceedingly warm weather episodes combined with, sometimes intense, rainfall (Vikhamar-Schuler et al. 2016). These extreme weather events have implications for snowpack, potentially destabilizing alpine snowpack (Conway and Benedict, n.d.; McCabe, Clark, and Hay 2007) contributing to avalanches, flooding, as well as impacting the alpine ecosystems with icing events. 

Despite Mount Washington being the tallest peak in New England with the summit situated in a sub-Arctic / alpine zone, it has not escaped the effects of regional climate changes. This study aims to accurately establish and quantify climate trends related to extreme weather events occurring on the summit of Mount Washington for the period of September 1989 through May of 2020.

Scope of Work
Predictions made by previous studies have stated how the frequency of ROS events will likely increase in high-elevation areas in the coming decades. Further examination of major factors such as snow water equivalent (SWE) of snowpack at all elevations, extent of snow cover before and after ROS events, freeze/thaw elevations throughout the event, and ground saturation and infiltration will aid in better understanding the development of these events as their frequency increases, especially with a global trend of increasing water cycle intensity.
External Relevance

Given the extent of damages caused by ROS events, their increasing frequency could have significant implications for the communities and ecosystems on and around Mount Washington. This is especially relevant given projected intensity increases in the global water cycle and extremely wet weather resulting from anthropogenic climate change.


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Kelsey, E. P., and E. Cinquino, 2021: The climatological rise in winter temperature-and dewpoint-based thaw events and their impact on snow depth on mount washington, new hampshire. J Appl Meteorol Climatol, 60, 1361–1370, https://doi.org/10.1175/JAMC-D-20-0254.1.

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Tao, J., X. Cheng, L. Zheng, X. X. Xiao, X. Y. Zhong, Q. Liang, Z. Q. Zhang, and H. Lin, 2023: Performance of climate reanalyses in the determination of pan-Arctic terrestrial rain-on-snow events. Advances in Climate Change Research, 14, 522–536, https://doi.org/10.1016/j.accre.2023.08.002.

Würzer, S., T. Jonas, N. Wever, and M. Lehning, 2016: Influence of initial snowpack properties on runoffformation during rain-on-snow events. J Hydrometeorol, 17, 1801–1815, https://doi.org/10.1175/JHM-D-15-0181.1.

Charlie Peachey, Weather Observer & Research/IT Specialist
Contributing Research: Laura Wilson