Transitional Climate Zone of the Russian North in Summer Conditions

This paper is concerned with the definition of the transitional climate zone of the Russian North through a complex of climate indicators and characteristics of the underlying surface, and its monitoring in the summer period based on the gradient analysis. The European part of Russia and Western Siberia north of 56° N are explored. These regions were determined by a cyclonic activity in Arctic front and notable cyclone repeatability in the summer period. The transitional climate zone in the Russian North can be identified by one or two indicators. On adjacent areas, these indicators can alternate and complement each other. Two key regions are distinguished on this territory. They are well defined by most of the parameters. One of these regions is situated in the northeast of the European part of Russia (Bolshezemelskaya and Yamalskaya tundras); it is determined by the cyclonic activity in Arctic front. It differentiates by areas with maximal gradients of temperature, humidity ratio, evapotranspiration (Ev), and NDVI, which are situated in 66°–67° N (landscapes of southern tundra, forest tundra, and border of northern taiga). The second key region is in the middle taiga zone of Western Siberia (62°–63° N), where the increased cyclone repeatability influences it, and it is characterized by horizontal contrasts of temperature, humidity ratio, NDVI and Ev. Here a zone of maximal gradients of Ev, and NDVI stretches between Ob and Yenisei rivers, strengthening in some areas. There is no significant trend of localization of the transitional climate zone on its indicators. According to climate conditions, maximal gradients of parameters can strengthen or weaken.

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