Preprint Article Version 1 Preserved in Portico This version is not peer-reviewed

Seasonal and Ephemeral Snowpacks of the Conterminous United States

Version 1 : Received: 19 November 2020 / Approved: 20 November 2020 / Online: 20 November 2020 (12:33:03 CET)

How to cite: Hatchett, B. Seasonal and Ephemeral Snowpacks of the Conterminous United States. Preprints 2020, 2020110545. Hatchett, B. Seasonal and Ephemeral Snowpacks of the Conterminous United States. Preprints 2020, 2020110545.


Snowpack seasonality in the conterminous United States (U.S.) is explored using a daily,14 km horizontal resolution gridded snow water equivalent and snow depth reanalysis product. I2calculated seasonal snowpacks using two established methods: (1) the classic Sturm approach that3requires 60 days of snow cover with a peak depth >50 cm and (2) the snow seasonality metric (SSM)4that only requires 60 days of continuous snow cover. The latter approach yields continuous values5from -1 to +1, where -1 (+1) indicates an ephemeral (seasonal) snowpack. Both approaches identify6seasonal snowpacks in western mountains and the northernmost central and eastern U.S. By relaxing7the depth constraint and providing continuous values, the SSM identifies greater areas of seasonal8snowpacks compared to the Sturm method, particularly in the upper Midwest, New England, and the9Intermountain West. Ephemeral snowpacks are identified throughout lower elevation regions of the10western U.S. and across a broad swath centered near 35°N spanning the lee of the Rocky Mountains11to the Atlantic coast. Because it lacks a depth constraint, the SSM approach is sensitive to interannual12variability, indicating it may inform the location of shallow but long-duration snowpacks at risk13of transitioning to becoming ephemeral with climatic change. A case study in Oregon during an14extreme snow drought year highlights seasonal to ephemeral snowpack transitions.


ephemeral snow; snowpack; seasonal snow; United States


Environmental and Earth Sciences, Atmospheric Science and Meteorology

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