Data from ERA5 reanalysis and observations at meteorological stations are used to estimate the spatiotemporal variations of extreme values of climatic and dangerous meteorological phenomena for the territory of Western Siberia over 1979–2020, and to identify the tendencies of their future variations during the late twenty-first century against the background of global climate change. The combined analysis of the derived estimates made it possible to identify the centers of “risk” in these areas and to determine the trends in their development. The air temperature is found to increase in the period 2011–2020 throughout Western Siberia, while the amount of precipitation and wind speed do so predominantly in its northern areas. Extreme precipitation amounts increase during summer in the entire area, except in mountainous areas in its southeastern part. In addition, areas affected by heavy rainfall are becoming smaller in the region and are located mainly in the south and along its western boundary. The results of the INM-CM5.0 model calculations revealed the response of the regional climate system to the ongoing global changes: the increasing trend in the number of extreme events in the region will persist until 2100.

A comparative statistical analysis of the spatiotemporal variability of atmospheric precipitation characteristics (mean and extreme values) in Western Siberia was performed based on data acquired from meteorological stations, global precipitation datasets such as the project of Asian Precipitation—Highly-Resolved Observational Data Integration Towards Evaluation (APHRODITE) and from Global Precipitation Climatology Centre (GPCC), and reanalysis archives, including from National Centers of Environmental Prediction (NCEP-DOE) and the European Center for Medium Range Weather Forecasts (ERA5) for the period 1979–2018. The best agreement of the values from the observational data was observed with the values from GPCC. This archive also represented the periodicities in the time series of observational data from meteorological stations, especially in the short-period part of the spectrum. Underestimated values were revealed for the APHRODITE archive, while overestimated ones were found for the NCEP reanalysis data. In comparison with GPCC, the ERA5 dataset reproduced the general variability but with a smaller amplitude (the correlation coefficient was up to 0.9). In general, the median estimates of the precipitation amount derived from the meteorological stations’ data, as well from the reanalysis data, were in better agreement with each other rather than their extreme values. However, their temporal variability can be effectively described by other datasets.

An analysis of the air-temperature and atmospheric-pressure fields in Western Siberia is performed based on observations in 1976–2014; a comparison of temperature and pressure variability in two temporal intervals, 1976–2005 and 1985–2014, is carried out. The estimation of contributions from such climate-forming factors as radiation and circulation is performed for the same intervals. It is revealed that an increase in the annual mean ground–air temperature in the investigated region of Western Siberia was still taking place in the period of 1985–2014; however, the warming process was less active than in the 1976–2005 period. Winter months play the largest role in decreasing the temperature growth rate; during these months, the warming process was replaced by a cooling one in the second time interval. It is shown that the circulation factors, that is, the mechanisms described by indices of global circulation, played the dominant role in the period from 1985 to 2014.

Latitudinal position and wind speed of the Southern Hemisphere subtropical jet stream have been investigated on the basis of ERA-Interim, JRA-55, and NCEP–NCAR reanalysis data for 1948–2013. The...

The analysis of asymmetry of probability distribution functions (PDF) is carried out for key atmospheric variables using the JRA-55 reanalysis data in the troposphere of the Northern Hemisphere for 1976–2014. The nonzero asymmetry of the PDF indicates the deviation of the PDF from the normal distribution. The analysis was carried out for two time-scale intervals: synoptic variability (SV) of 2–7 days and low-frequency variability (LV) of 9–30 days. Statistically significant deviations from the normal probability distribution occur in the regions of the most frequent formation of atmospheric baroclinic perturbations, i.e., over the western parts of the oceans in midlatitudes and downstream in the atmosphere. In the SV time-scale interval, a negative asymmetry of the vertical velocity is revealed in isobaric coordinates for the entire thickness of the free troposphere, which agrees with the overall dominance of cyclonic anomalies in this interval of time scales. In the LV interval, the asymmetry of this variable in the entire free troposphere is positive, which indicates the dominance of anticyclonic anomalies at these time scales. For the zonal velocity, temperature, and geopotential, the asymmetry sign of the PDF for variability with time scales of 2–7 days is different for the upper and lower free troposphere. The asymmetry of the PDF for atmospheric variables indicates the important role of the intermode interaction in the formation of baroclinic perturbations. The corresponding deviations of synoptic variability from the normal distribution, which is found in the upper troposphere of the subpolar and polar latitudes, can be related to the interaction of these perturbations with the winter polar vortex. These deviations of PDF from the normal distribution substantially increase the probability of the appearance of large (in absolute value) anomalies as compared to the case of the Gaussian PDF.