Dynamic climate changes and selectivity 124 of natural processes in the West Siberian Plain

The basis for the research was data from RIHMI - MDC database on average daily and average annual temperatures of surface air and precipitation in Omsk and Salekhard stations recorded for the period from 1936 to 2012. The data have been grouped into 4 periods: 1) 1936-2006, 2) 1936-1970, 3) 1971-2006, 4) 2001-2012. The study has revealed the spatial-temporal differences in the dynamics of thermal indices. For example, perennial rate of the average annual temperature on the Salekhard station increased significantly in the fourth period compared with the first period when the average annual temperature grew for 0,84 °C. This change means a lot for Subarctic's nature and one of results of these changes is melting permafrost. The change in long-term average air temperatures and indices of their variability from period to period were more pronounced in Omsk station. From the first period to the second one, the average temperature level increased 3 times and the coefficient of variation reduced by about the same times. During the period from 2001 to 2012, the average temperature level increased more compared with 1936-1970. In this work, we have obtained median of five-year average annual air temperatures and amount of precipitation for two periods: 1883-2012 and 1936-2012 in order to study cyclical fluctuations in values over time. Analysis of median progress curve of average air temperatures has appeared to distinguish two centennial cycles at the Salekhard Weather Stations. The centennial cycles have not been detected in the steppe zone. We have also detected ranges/limits for shorter cycles closer to the length of a solar cycle: four of them are at the Salekhard station lasted 13-29 years, and 5 cycles are at the Omsk station lasted 11-20 years. 6 cycles at the Salekhard station and 8 cycles at the Omsk station are distinguished on the median progress curve of average annual temperatures and precipitation. Last ones along with thermal ones do not have upper limit. The climatic characteristics were drawn up for each cycle, assessment of the abnormality degree of the hydrothermal regime was given, and the comparative analysis was conducted. It should be noted that cyclical fluctuations in temporal sequences/series of average annual precipitation and air temperatures occur along with increase of their values. After analyzing the materials and data from paleo geographic research for a quater, authors endorse views of V.M. Kotlyakov that modern climatic changes are not a new phenomenon in Earth evolution.

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