Satellite derived snow cover data for 22 years and snow depth data for nine years over Eurasia have been analyzed to reexamine the possible relation fo snow with the Indian summer monsoon. In contrast to the previous studies which use snow cover averaged over all of Eurasia as a single number, the frequency of occurence of snow at each grid point over Eurasia is correlated with the Indian summer monsoon rainfall. Thus the specific geographical regions over Eurasia which are responsible for the well known inverse relationship between Eurasian snow cover and the Indian monsoon rainfall are delineated.
It is found, somewhat suprisingly, that western Eurasia is the only geograhical region for which a moderately significant inverse correlation exists between the winter snow and subsequent summer monsoon rainfall. Composites for high and low snow years have also been studied using temperature data. Winters of high (low) snow cover for western Eurasia are found to be associated with colder (warmer) temperatures for large regions of the Eurasian continent. These temperature anomalies persist until the pre-monsoon months, giving rise to higher land-ocean meridional temperature contrast for low snow years. Composite wind anomalies have also been examined and found to exhibit systematic differences at the 200mb level.
Snow cover and snow depth anomalies for years of high and low Eurasian snow cover, and high and low monsoon reainfall have been composited. An EOF analysis of seasonal snow cover anomalies has also been conducted to examine the principal modes of variability.
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Center for Ocean-Land-Atmosphere Studies
last update: 29 July 1998
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