Remote sensing from satellites delivers quite real imagery of snow cover distribution in global scale. Snow extents by late winter over almost 60 % of mainland northern Hemisphere and occupies about 25 % of the southern one. This defines the reflectance of solar radiation or the snow surface albedo which amounts to 0.80-0.90 for fresh fallen snow, while the forest terrain of no snow reflects usually 0.16-0.19 of the global solar energy flux. Thereafter, the snow cover becomes as a switchboard for the energy balance of the planet Earth as well as a power forcing the atmospheric circulation.

At the same time, the circulation systems manage the extent and propagation of snow cover. In Europe, the border of snow advances southwards by western type of atmospheric circulation. Eastern types prevailed promote to make snow cover more persistent. This fact proceeds from close interrelations between atmospheric circulation type, atmospheric water vapor content and precipitation. Thus, the circulation gears the components of the water cycle and snow cover, rebuilds the energy balance over the earth surface and creates the temperature anomalies in global scale.

As the satellite imagery showed, the snow covered area over the northern Hemisphere changes from 41 to 48 millions km² in winter, and from 27.5 to 34 ones in spring. Besides it tends to decreasing that is perceived just for spring months. Perhaps, gradual global warming presumed as human impact leads to earlier snowmelt season. Nevertheless, the global snow cover does not digress generally, in opposite, the big anomalies take place such as sudden snowfalls by cold air breaks at late spring and unforeseen long-time periods with snow near the south boundaries of snow covered area in western North America, Central Asia and Asia Minor.

By detail analyzing the satellite imagery and synoptic maps, one may suppose that the snow cover is conditioning by weather and, on the other hand, it affects the future weather conditions themselves. The anomalies in snow cover distribution over wide regions, for instance, over the Russian plains, affect so steady temperature anomalies at early spring, that it may be predicted in a due time as to be there of great importance for the cereal crop agriculture.

Hydrosphere © 1990 — 2005 Vladimir A. Shutov
Design by Timothy (Azs) Shutov © 2001