WINTER SNOW DEPTH VARIABILITY OVER NORTHERN EURASIA IN RELATION TO RECENT ATMOSPHERIC CIRCULATION CHANGESстатья
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Аннотация:Mean snow depth time-series for February (1936-2001) over the Northern Eurasia (incl. Norway, Finland and former USSR), interpolated into 5x5o grid points, are studied using empirical orthogonal function (EOF) analysis. First five statistically significant rotated PCs are correlated to Northern Hemisphere (NH) Teleconnection patterns at the 700 hPa height: North Atlantic Oscillation (NAO), Polar-Eurasia (Pol), Pacific-North American (PNA), West Pacific (WP), Scandinavian (Scand). Impact of the NH circulation modes on snow depth variations is evaluated using the multiple stepwise backward regression.
Analyses of the snow depth PCs indicate that within the Northern Eurasia territory, there are several regions with snow accumulation, respondent to certain circulation modes. PC1 describes low-frequency snow depth variation to the north from 55-60oN between the White Sea and river Lena basin, and is positively correlated with NAO and negatively – with Scand. MSBR shows that in 1951-1974 the leading role in snow depth variability belongs to the Scand. After 1975, Scand has passed over the leading role to NAO. Scand and NAO are also responsible for the surface air temperature changes over the Northern Eurasia. Snow depth PC1 and wintertime temperature are correlated very close to each other. The PC2 describes quasi-decadal snow depth variability over the Eastern Europe and is negatively correlated with NAO. For the Baltic and White Sea coasts, Fennoscandia, and the centre of the East European plain, decrease of snow accumulation, related to positive NAO phase, seems to be caused by mild winters. For the southwestern and central regions of Eastern Europe, negative snow depth anomalies could also be caused by decrease of precipitation associated with the eastward shift of cyclone tracks related to the positive NAO phase. Two regions, where snow depth variations are described by PC1 and PC2 respectively, reveal the border between the opposite recent tendencies of snow accumulation.