HISTORICAL SNOW COVER VARIABILITY IN THE GREAT PLAINS REGION OF THE USA: 1910 THROUGH TO 1993

Abstract

The duration of seasonal (September–May) snow cover over the central and northern Great Plains region of the USA has varied considerably during this past century. Annual and decadal fluctuations are embedded in a statistically significant trend toward greater seasonal snow cover, from 29 days in the early part of the century to 38 days in recent decades. The variability of snow cover duration also increased throughout the century, exhibiting the largest changes in a north-west-trending zone bisecting the region. Seasonal snowfall, temperature, and precipitation show fluctuations similar to those of snow cover; however, only snowfall has increased significantly since 1910. A post-1970 shift toward longer autumn (September–November) snow cover duration and shorter spring (March–May) duration has been accompanied by decreases in autumn maximum and minimum temperatures and increases in spring minimum temperatures. The reliance on snow cover for hydrological 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, necessitate increased study and hence a better understanding of the variability of snow cover over the Plains.