Seasonal Features of the Changes in the Frequency of Severe Weather Events in Russian Regions over the Past Decades

The changes in the frequency of severe weather events and their seasonal features in Russian regions are analyzed using the data for 1998–2021. More than 2/5 of severe weather events are observed in summer, which is also characterized by the greatest increase in the frequency in the recent decades: by almost 1.5 times, with an increase of 1 K in the Northern Hemisphere surface air temperature. The frequency of extreme events also significantly increases in spring, while the minimum relative increase was found for winter. Significant changes have been identified: in the recent years, there has been at least one severe weather event per day averagely and two to three such events per day in summer. Correlation of the detected trends (in particular, a more significant increase in the frequency of severe weather events in summer months) with the changes in the temperature stratification and moisture capacity of the atmosphere and the intensification of convective processes in the atmosphere under warming has been found. Against the background of the general increasing trend in the frequency of extreme weather events, some features associated with key modes of climate variability (these peculiarities are manifested, in particular, in the atmospheric blocking patterns) are noted in the recent decades.