Long-term dynamics of the Siberian Anticyclone characteristics based on reanalysis data (1950-2024)

Abstract

This study presents a statistical analysis of the temporal variability of the Siberian High (SH), based on the Siberian High Index (SHI). The index was calculated using ERA5 reanalysis data over a 75-year period (1950-2024). A comprehensive statistical assessment of the SHI series was performed, including the development of objective criteria for identifying significant phases, and the investigation of seasonal features and the temporal structure of the long-term series. The results reveal a qualitative shift in the pressure regime of the SH in recent

decades. Beginning in the 21st century, a steady increase in decadal mean index

values is observed, culminating in their shift into positive territory in the 2010s. Concurrently, since the late 20th century, there has been a trend towards reduced interannual variability of the SHI, as indicated by a decreasing standard deviation (а). This suggests a transition towards a more stable anticyclonic weather regime over Siberia in recent decades. Despite this long-term trend, the overall distribution of statistically significant deviations remains nearly balanced (24.8% positive and 24.6% negative anomalies), underscoring the persistent and dominant role of natural variability within the SHI series.

Keywords. Siberian High, Siberian High Index (SHI), atmospheric circulation variability, climate trend, ERA5, extreme events, quartiles, standard deviation.