Seasonal cycle of snow cover changes in Eastern Siberia and its synoptic preconditions

Аннотация

The seasonal cycle of snow cover in Eastern Siberia is characterized, and synoptic preconditions of snow accumulation in winter and snow ablation in spring are determined using daily datasets. It was ascertained that cyclone activity has a strong impact on the occurrence of abundant snowfalls in Eastern Siberia. Negative anomalies of sea level pressure (SLP) usually spread westward or southwestward from the place of recorded substantial snowfalls, and they are associated with positive anomalies of air temperature located to the east or northeast of SLP depressions. Cyclonic circulation causes inflow of relatively warm and humid southern air masses originating from the Pacific Ocean, to the eastern parts of cyclones. During the days with snow ablation in spring much lower SLP anomalies occur than during snow accumulation in winter. This may suggest smaller influence of air circulation on snow cover reduction in spring and higher impact of insolation; both result in strong positive anomalies of air temperature which extend over entire Asia. These findings imply that the position, intensity, and dimension of pressure patterns are crucial for determining the location and intensity of rapid changes in snow cover depth during the snow cover season in Eastern Siberia.