VARIABILITY OF TEMPORAL CHARACTERISTICS OF SNOW COVER IN SIBERIA ON GROUND-BASED DATA

Estimates of the variability in the dates of the beginning snow cover formation and end of its descent, the establishing and destruction of stable snow cover, the duration these periods, the number of intervals with stable snow cover in the cold season, as well as the duration of the periods of formation and descent of snow cover were obtained in this paper. Differences in the behavior of these characteristics depending on the geographical features of the territory were analyzed. Four groups of stations were considered: low-lying (up to 50 m) stations, high-lying (from 700 m), stations in Western Siberia (60-90ºE) and in Eastern Siberia (90-120ºE). The snow cover ground-based observations data (RIHMI-WDC) for Western and Eastern Siberia over the time period from 1970 to 2019 was used. Along with the general period (1970–2019) the behavior of these characteristics for two subperiods of 1977–2005 and 2006–2019 corresponding to the zonal and meridional circulation epochs was considered. The response of the snow cover to the change in the atmospheric circulation has been obtained. With the prevailing meridional circulation, in comparison with the zonal circulation, the beginning of the snow cover formation occurs later and synchronously at most of the stations of each of the specified geographical groups, and the snow cover descends earlier, but at the same time is much more non-uniform in time (non-simultaneous) within a geographic group. A smaller number of intervals with a stable snow cover in cold season is also shown, which means more stable snow cover during the cold season in meridional circulation epoch then in zonal. An increase in the duration of the snow cover formation and descent time periods was obtained for all the considered geographical groups of stations. The exception is for low-lying station group only. Thus, the conditions of the meridional circulation epoch not only compensate for the changes that occurred in the zonal epoch, but also bring new changes in the temporal characteristics of the Siberian snow cover.