Trends in Snow Cover in the Continental United States (1950-2010)

Abstract:

Snow cover plays many roles across the U.S., with local impacts ranging from traffic disruption to the provision of ecological services to a wide variety of flora and fauna. Snowpacks are integral to many regions' water supply and management strategies. Snow cover also alters surface albedo, providing an important feedback in the climate system. The main objective of this study is to diagnose and understand the spatial patterns of any trends in snow cover frequency, magnitude, and persistence using National Climatic Data Center's Cooperative Observer Network (COOP) data supplemented with Natural Resources Conservation Service's Snow Telemetry (SNOTEL) data. The station data are investigated over the period 1950-2010 directly and without spatial averaging. Additionally, a subset of the COOP stations, selected for relative homogeneity with regard to stations moves, time-of-observation changes, instrument changes, and other disruptive factors, are analyzed to assess any disagreements with trend patterns in the full dataset. Temporal variability underlying the long-term trends is also examined. Key results include widespread declines in the length of the snow-cover season (the period between first and last days of snow cover at a site) and in the total number of days with snow cover per year. Trends in occurrence of snow cover are most pronounced toward the end of the snow-cover season (spring-summer), and occur despite a widespread increase in precipitation.