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CR prepress abstract   -  DOI: https://doi.org/10.3354/cr01687

North American rain-on-snow ablation climatology

Z. J. Suriano

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ABSTRACT: Rain-on-snow ablation events carry a relatively high risk for rapid snowmelt and runoff due to the combination of liquid precipitation and generally high turbulent fluxes into the snowpack. Determining the variability in rain-on-snow ablation is critical in describing local hydroclimate. This study uses a gridded observational snow dataset to examine spatiotemporal variations in North American rain-on-snow ablation over a 50-year period. Here we show rain-on-snow ablation represents approximately 33% of all ablation events in the eastern third of the continent, compared to less than 20% in its interior. Rain-on-snow ablation was most frequent along the western and eastern coasts of the continent, with over 10 events observed per year on average. A central band of enhanced event frequencies propagated meridionally during the calendar year, most prominently in the eastern half of the continent. Seasonal (Sep-Aug) event frequency from 1960-2009 significantly decreased by approximately 50% across much of northern Quebec and in the southern Appalachians, while significantly increased in portions of British Columbia and southeastern Quebec. Inter-annual variations in event frequency were primarily forced by variations in seasonal-scale snowfall and snow depth, and only moderately associated with variations in air temperatures.