ИСТИНА

Variations of principal circulation modes have significant effect on statistics of cyclones/anticyclones and blocking not only within domains of these modes, but also far downflow (and sometimes upflow). A comprehensive analysis based on the archive of cyclone and anticyclone tracks computed from baric fields of the NCEP/NCAR Reanalysis using author’s identification method and several circulation indices reveals principal features of these effects. Large-scale circulation systems of the Atlantic sector, especially NAO and Scandinavian (SCA) modes are known to have a strong effect on surface temperature variations in North Eurasia, most pronounced in winter, late autumn and early spring. Particularly winter temperature over Russia demonstrates a strong oscillation of a period about 35 years with an amplitude of about 1.5-2C superimposed with a global warming trend. This effect, at least partly, may be connected with a large displacement of anticyclonic blocking systems from the Urals –Western Siberia to European Russia between warm and cold phase of the mentioned oscillation. Associated temperature patterns are studied. The global warming trend is not geographically and seasonally uniform, and it occurs on the background of natural variations. Winter trend over Russia estimated directly from the time series of observations varies from 0.15C/decade for 1976-2014 to 0.33C /decade for 1976-2017, both insignificant at 5%. However, a simple statistical model that uses as regressors indices of NAO and SCA plus a piecewise-linear function of year equal to zero before 1976 and year thereafter (regression coefficient of this regressor is simply linear trend) separates contributions from natural variations and trend. It demonstrates that trend is close to the observed for the period 1976-2017 (when presumably a full cycle occurs) and highly significant.