The Relationship Between Eurasian Snow Cover And The Northern Hemisphere Atmospheric Circulation

Based on the weekly snow cover data in the Eurasia from 1973 to 2004provided by NOAA-NESDIS, the spatial/temporal characteristics of snow coveranomaly over Eurasia are studied. Results show the Qinghai-Tibet Plateau and theHimalayan region in four seasons is a very large snow cover anomaly region. Fromthe long-term change, autumn and winter snow-covered area of the Eurasiancontinent perform weak increasing trend, and then spring and summer showsignificant decreasing trend. The relationships between the autumn-time andwinter-time snow cover anomalies and the distributions of winter-time NHcirculation have been investigated by using comparative analysis of the correlationand synthetic methods. The results show:1. The abnormal distribution of snow cover changes the heating surfaceimposed on the atmosphere through its unusual cooling effect, ultimately causingatmospheric circulation adjustments. In heavy snow cover years, the surfacetemperature of Eurasia is negative anomaly, the heating of surface forced on theatmospheric weakened, the air temperature of Eurasia is also negative anomaly, and500hPa height field of the Eurasian continent becomes lower. However, in lightsnow cover years, the situation is opposite.2. The relation between autumn-time snow cover anomalies and followingwinter-time circulation is closer than it between winter-time snow cover anomaliesand winter-time circulation base on observing analysis. There is a significantlynegative correlation between Eurasian snow cover in autumn and Arctic Oscillationor the North Atlantic Oscillation in winter. Correlation analysis between climateindices of the northern hemisphere and the index of Eurasian snow cover shows thatthe relationship between Eurasian autumn or winter snow cover and spring AO orNAO is not good.