Trends in Changes in the Duration of Thunderstorms and Atmospheric Blocking over the Caspian Region Under Current Climate Conditions

This study analyzes the interannual trends in the Total Duration of Thunderstorms (TDT) in the Northern Caspian Region (Atyrau region, Kazakhstan). While TDT has generally increased, consistent with Northern Eurasian trends, a sustained local decrease was observed in the 21st century. We propose that the observed local decrease in TDT may result from the stabilizing influence of the Total Duration of Atmospheric Blocking (TDB), which could counteract thermal convection enhanced by climate warming. To evaluate this relationship, trends in TDT (from nine meteorological stations) and TDB (from ERA5 reanalysis) for May–August were analyzed over 30-year and 10-year periods. The analysis confirmed a stable inverse relationship between TDT and TDB trends, which is particularly strong in June and August. This verifies the dominant role of atmospheric blocking in suppressing convective activity. Given the high spatial coherence of TDB trends, these findings are generalized to the entire Caspian region. The research confirms that rising TDB acts as a crucial regulator of thunderstorm activity. The correlation coefficients between the number of thunderstorms and the recurrence of atmospheric blocking events at all stations range from 0.88 to 0.95. Projections indicate that if current TDB trends persist under ongoing warming, spring–summer TDT will continue to decline. Overall results suggest that if current TDB trends persist under ongoing warming, TDT during the spring–summer period is likely to continue declining.