North American snow cover variability from satellite data (1972-1993) and comparison with model output

A twenty-one year record of remotely-sensed areal snow cover fluctuations for the Northern Hemisphere is examined, with particular emphasis placed on North America. No trend is apparent, but several periods of positive and negative departures are found. The mid- to late-1970s, and the mid 1980s, had large snow covered areas. The early 1980s, and the period since 1987, are characterized by low snow cover. The most temporally extensive of these has been a period of snow deficit since 1987, particularly in spring and in eastern North America. The five lowest North American spring snow covers on record have occurred since 1987. In autumn, three of the last five years have been extremely low. Recent winters have not been anomalous. Results from one climate model are compared to observations, and are found to simulate accurately winter snow cover on the continental scale, while slightly under-estimating spring and autumn values. On the regional scale, the model is less accurate. Snow cover may be critical for model validation, improvement of parameterizations, and for prediction and detection of climate change.