Circulation Factors for the Current Low Water Level within the Lake Baikal Drainage Basin

Аннотация

We examined the relationships between the dynamics of surface inflow into Lake Baikal and the runoff of the main tributaries of the Baikal drainage basin and regional and global circulation parameters to determine the role of certain of the meteorological factors in the current low water level within the Baikal catchment area. A decrease or an increase in the runoff of Baikal’s rivers in the summer months depends on the synoptic situation in the south of East Siberia and in the north of Mongolia where southern cyclones provide the main influx of moisture to the Baikal region. We used different indices as climatic and circulation factors which characterize the specific features in the forms of atmospheric circulation in high and low latitudes of the northern hemisphere (NAO, AO, SCAND, and others) as well as the anomalies of mean monthly values of surface pressure and geopotential heights of isobaric surface AT-500 in the zone of 43–50°N and 90–115°E. It was found that the low water level within the Lake Baikal drainage basin has persisted since 1996 but it has manifested itself particularly clearly due to the lake stage reduction. In the south of Siberia and in the north of Mongolia, since the early 21^st century there has been an enhancement in anticyclogenesis processes accompanied by an increase in air temperature, surface pressure and geopotential altitudes at the level of the mid-troposphere (5 km). The more favorable conditions for river runoff formation are created during the development of the ridge of elevated and low pressure over Ural and the associated ridge of low pressure over Siberia, with cyclogenesis processes occurring in front of them over the territory of Mongolia and the south of East Siberia at the Earth’s surface. Elevated precipitation and runoff are observed at the time of blocking anticyclones over Transbaikalia and the Far East, which are responsible for a long-lasting persistence of Mongolian cyclones.