Patterns of seasonal maximum snow-water equivalent over the Northern Great Plains of the United States analyzed using hybrid-modeled climatology

Abstract

Over the last 20 yr across North America, satellite and in situ observations have indi- cated a reduction both in the number of snow-cover days and in snow-cover extent in the spring. From a hydrologic perspective, however, the water content of the snowpack is most important. Few studies have examined whether the changes in snow-cover days or snow-cover extent corresponded to changes in the water content of the snowpack. This is due largely to the problems with obtaining quality data on the snow-water equivalent (SWE). This paper uses a long-term, high-resolution hybrid SWE climatology to examine peak seasonal SWE and its impact on the hydrology of the North- ern Great Plains. Accumulations of peak SWE, most frequently occurring in February, are greatest over NE Minnesota and decrease towards the south and southwest. There are no long-term trends in the magnitude of SWE, but there are distinct decadal-scale patterns of above- and below-average SWE. In general, the 1950s were below average, the mid-1960s through the 1970s were above average, and the 1980s and early 1990s were again below average. Greater maximum seasonal SWE corresponds with longer snow persistence in the spring and greater March snow-cover area.