Numerical simulation of severe weather phenomena on the territory of Western Siberia

Recently, researchers are increasingly using physical and mathematical numerical models to solve problems in meteorology and climatology. The special value of using these models is given by the ability to recreate a variety of situations with severe weather phenomena (hurricanes, heavy showers, severe frost, etc.). The Weather Research and Forecasting (WRF) predictive model is used in this research. The WRF model is a mesoscale numerical weather prediction system designed for both atmospheric research and operational forecasting applications. The model serves a wide range of meteorological applications across scales from tens of meters to thousands of kilometers. This model is also suitable for calculating the likelihood of occurrence of extreme events in the study area. The region of Western Siberia was chosen as the study area with coordinates 47°–63°N and 65°–105°E. A rare meteostation network on such a vast territory does not make it possible to study and predict factors leading to severe weather phenomena. Modeling is used to eliminate this problem. This paper examines two cases in this region with severe weather events over 2019-2020. The first case is a situation with the occurrence of a large temperature gradient in the lower atmosphere on April 30, 2019, during the development of abnormally early thunderstorms and squalls. Since April 28, 2019, significant spatio-temporal changes in many meteorological and geophysical parameters have taken place on the territory of Western Siberia, due to the displacement of the polar main front far to the north and the short-term invasion of the tropical air mass, as well as the subsequent passage of the cold front and the onset of the Arctic air mass. The second case is a situation with the emergence of a large area of anomalous cold wave on the territory of Western Siberia on December 25–27, 2020. Since December 22, the formation of an anticyclone with a value of 1035 hPa with a center near the Severnaya Zemlya archipelago has been recorded. By December 24, its center increased to 1050 hPa. As the Arctic front moved to the southeast, the formation of a high pressure ridge was noted, which was directed to the south of Western Siberia. During this period, cloudiness cleared over most of Western Siberia, as well as high values of atmospheric pressure (1030–1040 hPa) and a sharp drop in air temperature with an average daily air temperature below the climatic norm by 9 °C and more to -40 °C and below. To check the simulation results, observational data from 211 meteorological stations were used. An analysis of the comparison of the simulation results with the observed values of the fields of meteorological parameters gives a satisfactory assessment of the reproduction of these fields. The WRF model has shown that it adequately reproduces the occurrence of convective systems and correctly calculates the conditions for the occurrence of factors (for example, a sharp increase in the pressure field, advection of cold air, radiation cooling) leading to severe weather phenomena