Snow cover variability in the Great Plains of the United States: 1910-1988

The duration of seasonal (September-May) snow cover over the Great Plains of the United States has varied considerably this past century. A statistically significant trend toward a greater duration of snow cover from 1910 to 1988 shows region-wide average of 29 days early in the century increasing to 38 days in recent decades. Variability of snow cover duration from year to year has also increased, exhibiting the largest changes in the northwest, central and southeastern parts of the region. Fluctuations on the order of a decade are imbedded in this upward trend i.e., low snow cover in the 1930s, and high snow cover in the 1970s. Decadal variations are associated with changes in both snowfall and temperature; however, only snowfall has shown a statistically significant increase since 1910. The reliance on snow cover for hydrologic and agricultural purposes in this part of the country, the sensitivity of the boundary layer climate to snow cover conditions in the Plains, and the projections by global climate models for this region to become warmer and dryer as a result of increasing atmospheric concentrations of greenhouse gases, necessitates a better understanding of the variability of snow cover over the Plains.