Large-scale Heat Waves in the South of European Russia

Abstract

For large-scale heat waves that occur in the south of the European part of Russia (EPR), the frequency variability since the beginning of the 20th century is considered, including variations on decadal scales and a trend during the global warming period, accompanying variations in the aridity index SPI, and the structure of the longest waves. The geographic distribution of air temperature anomalies on the territory of the Russian Federation, large-scale circulation conditions, the North Atlantic sea surface temperature (SST) anomalies, which accompanied heat waves in the south of the EPR, are analyzed using the composite analysis. In particular, the wave structure was revealed of the composite field of the air temperature anomaly for days with heat waves and the related 500 hPa geopotential height ($H_{500}$) fields over Russia. The $H_{500}$ field structure generally corresponds to the negative phase of the East Atlantic–Western Russia (EAWR) circulation pattern. Similar structures of the geopotential field are observed during heat waves in the northern half of the EPR. However, in this case, there are specific features that contribute to the inflow of cold air from the north to the southern regions. It is shown that the values of the EAWR index are significantly shifted towards negative values in the months when long heat waves occur over the southern EPR. The waves are accompanied by positive anomalies of the North Atlantic SST and the strongly increased blocking anticyclone activity. The downward trend in the EAWR index observed in recent decades and the SST rise expected with the global warming increase a risk of droughts in the main grain-producing region of the country.