| Abstrakt: |
It is revealed that there was a significant increase in the Bowen ratio in the Volga, Southern, and North Caucasian federal districts in the second half of the 20th century–beginning of the 21st century. This indicates a strengthening of sensible heat flux and a reduction of latent heat flux in the heat and moisture balance. These changes are caused by a significant temperature rise, especially in the south of European Russia, with a regional decrease in precipitation. The Bowen ratio is inversely proportional to precipitation and NDVI and directly proportional to temperature. In the steppe zone represented by the Volga, Southern, and North Caucasian federal districts the long periods of predominance of the Bowen ratio anomalies of a certain sign can be distinguished for June and July: the positive ones in the 1950s and until the mid-1960s, the negative ones after that until the early 2000s, and the positive ones since the middle of the first decade of the 21st century. Since the second decade of the 21st century, the positive anomalies of the Bowen ratio have become more frequent in some years and have exceeded the standard deviation. An increase in the contribution of heat to the heat and moisture exchange balance led to a degradation of vegetation conditions in the Volga, Southern, and North Caucasus federal districts. In the south of the Siberian Federal District, the fluctuation of the Bowen ratio anomalies is less pronounced than in European Russia, which suggests some stability of heat and moisture supply in summer over the past 70 years. [ABSTRACT FROM AUTHOR] |
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