Identification of grain-producing areas vulnerable to moisture deficiency under climate change based on meso-zoning of the dry farming cropland in European Russia

Long-term deficits of atmospheric moisture cause droughts, which, in case of their large-scale spread and exceptional severity, are hazardous natural disasters. Therefore, identifying the causes of drought, the driving mechanisms of its spread, and assessing droughts by the time of their onset, duration, intensity and frequency are the focus of attention of researchers around the world in the context of increasing climate change. In such studies, the analysis of spatiotemporal changes in precipitation deficit comes to the fore, and its changes are associated with the manifestation of climate variability and intensified anthropogenic impact on the climate. Their relevance is due to very large contribution of semiarid regions to the world production of high-quality grain, since the world food supply depends on the stability of the final yields. The Dry Farming Cropland (DFC), an agricultural region with an unstable precipitation regime, is located in the middle part of European Russia and covers the Central Black Earth region, the Middle Volga region and the south of the Urals where valuable cultivars of spring small grain cereals are grown. The novelty of our study lies in the fact that the boundaries of vulnerable grain-producing territories in the eastern part of the DFC are delineated based on a set of quantitative criteria and qualitative characteristics of which agro climatic indicators of extreme aridity are of paramount importance. This paper is the first to submit data on the delineation we obtained. For the first time, we have quantitatively shown that in a changing climate, more northern and moist grain-producing territories become comparable to more southern and drier grain-producing territories in terms of susceptibility to extreme moisture deficiency. In addition, the greatest decrease in the precipitation absolute minimum with an increasing frequency of years with sharp deficits is characteristic of low-relief landscapes. Our goal was to develop the DFC meso-zoning for identification of areas vulnerable to atmospheric moisture deficiency under climate change to provide effective management of the risks during final yield formation in early spring crops. Geographic coordinates and altitude above sea level were indicated for 32 agrometeorological stations with homogeneous data series from 1945 to 2021 located in the unstable moisture zone of European Russia. The boundaries of the unstable moisture zone were determined based on the agro climatic conditions, data on crop location and concentration, and on indicators of weather and climatic variability of yields. Time intervals were selected for both a long sequence of years and periods during the growing season. Based on the characterization of anomalies in globally averaged surface air temperature from 1880 to 2021, two periods identified were 1945-1980 and 1981-2021. The sowing-heading dates were chosen as the period during which weather conditions directly affect the final yield of spring grain crops. For all stations, these periods closely coincided, covering May and June. Soil criteria included qualitative characteristics and quantitative indicators. Landscape criteria included latitudinal zonation which determines the change in landscape types, longitudinal component which influences some northward shift of steppe landscapes as we move deeper into the continent, and the altitude layers of landscapes. Mesozonation is based on the transition from zonal schemes to subregional levels based on their agro climatic, soil and landscape features. Initially, this provides dividing the DFC into two parts with the opposite trends in changes of aridity, the less vulnerable western part and the more vulnerable eastern part. In 1946 and 1981, extreme precipitation deficits occurred in areas west of the middle Volga, as influenced by the zonal type of atmospheric circulation. In 1975, 1998 and 2010, it covered a very vast territory, including areas east of the middle Volga, where the influence of the meridional type of atmospheric circulation occurred. Since 1975 belongs to the first period, and 1998 and 2010 belong to the second, the ratio of such years by period was 1:2. This indicates that in the future, we cannot exclude an increase in large-scale sharp deficits of atmospheric moisture, leading to catastrophic droughts, which requires the development of measures to mitigate drought consequences. These results also draw to conclusion that in the unstable moisture zone of European Russia, shifts to a northern direction occur, involving more humid areas of vulnerable grain-producing territories. Globally, this is consistent with the general trend of severe droughts spreading towards the poles.