Long-period Variations in Extreme Temperature Statistics in Russia as Linked to the Changes in Large-scale Atmospheric Circulation and Global Warming

Some aspects of long-term variability of temperature extremes on the territory of Russia are considered using average daily surface air temperature data from 367 weather stations over the period of 1960-2016. The number of days with extremely high summer temperature has increased monotonously (with strong peaks in some years) in the European part of Russia since the 1980s; in the Asian part of Russia this growth stopped in the early 2000s. The number of cold extremes has decreased. Changes in winter mainly agree with the general warming, but in the Asian part of Russia the warming trend is superimposed by about 40-year oscillations resembling variations in the leading atmospheric circulation modes: the North Atlantic Oscillation (NAO) and the Scandinavian pattern. The statistics of indices of extremes in the opposite phases of the modes revealed a strong response in winter, which explains qualitatively the features of long-term variations in temperature extremes. A difference in composites between the positive and negative NAO phases is mostly negative for cold extremes and positive for warm ones. The response to the Scandinavian mode is opposite. In summer, the response is generally weak, but in the west of the European part of Russia the heat wave duration is strongly linked to variations in the Scandinavian pattern.