During the 2010 summer, a severe drought impacted Western Russia, including regions surrounding Moscow and Belgorod (about 700 km south of Moscow). The drought was accompanied by high temperatures. Moscow recorded 37.8°C (100°F) for the first time in over 130 years of record keeping. The record heat, high humidity, dry weather, and smoke from forest fires caused increased human mortality rates in the Moscow region during the summer. The excessive heat and humidity in Western Russia were the result of atmospheric blocking from June through mid-August. The NCAR-NCEP reanalyses were used to examine blocking in the Eastern European and Western Russia sector during the spring and summer seasons from 1970 to 2012. We found that drier years were correlated with stronger and more persistent blocking during the spring and summer seasons. During these years, the Moscow region was drier in the summer and Belgorod during the spring seasons. In the Moscow region, the drier summers were correlated with transitions from El Niño to La Niña, but the opposite was true in the Belgorod region. Synoptic flow regimes were then analyzed and support the contention that dry years are associated with more blocking and El Niño transitions.

A meridional Northern Hemisphere (NH) circulation epoch, which began in 1957, is marked by changes in the temperature and precipitation regimes over southwest Russia and central USA depending on the occurrence of NH atmospheric circulation regimes. A classification scheme proposed in 1968, and studied later put forth 13 NH circulation types, fitting more broadly into four groups, two of which are more zonal type flows and two of which are more meridional flows. Using the results of a previous study that showed four distinct sub-periods during the 1957–2017 epoch, the temperature and precipitation regimes of both regions were studied across all seasons in order to characterize modern day climate variability and their suitability for vegetation growth. Then the Hydrologic Coefficient, which combined the temperature and precipitation variables, was briefly studied. The most optimal conditions for vegetation growth, positive temperature and precipitation anomalies, were noted during the period 1970–1980 for southwest Russia, which was dominated by an increasingly more zonal flow regime in the Belgorod region and NH in general. For the central USA, the HTC showed more ideal conditions for agriculture in recent years due to favorable precipitation occurrence. In southwest Russia, variable precipitation regimes were noted during the meridional flow periods, and with the increase in temperature (since 1998), these can adversely affect the hydrothermal characteristics of the growing season. Finally, a comparison of the 13 NH circulation types with several teleconnection indexes demonstrated the robustness of the NH flow regime classification scheme used here.

The goal of this research is to evaluate changes in temperature and precipitation in the Central Chernozem Region of southwestern Russia during the summer and relate these to large-scale circulation types and synoptic circulation processes. Some of these circulation regimes result in extreme weather conditions over the region. Using a classification system for Northern Hemisphere large-scale flow regimes and observations of weather within the Central Chernozem Region, the role of individual synoptic patterns in the formation of weather anomalies was identified. Also, comparing the periods 1981–2010 and 1971–2000, the mean summer temperatures increased by 0.6°C regionally. During the most recent decade the increase was 1.3°C. Total precipitation for the summer increased over the 20th century and was characterized by less variability during the second half when compared to the first half. However, in the beginning of the 21st century, precipitation has decreased during the growing season, but variability has increased. The increase in summer temperatures and increased variability in precipitation were then linked to an increase in the occurrence of weather regimes associated with warm anomalies and blocking. Finally, the results of this study can be used to translate larger-scale seasonal or climate forecasts to the regional scale.

Changes in the general circulation of the atmosphere have been taking place during the latter part of the twentieth century and the early part of the twenty-first century. In the Belgorod region of Southwest Russia, this has been manifested in the more frequent occurrence of stationary anticyclones, including those referred to as blocking anticyclones, especially during the summer season. Also, there has been a general increase in regional temperatures during the growing season over the period mentioned above, and combined with the more frequent occurrence of anticyclones has led to less humid conditions. In the Missouri region of the Central USA, variability in the circulation on differing time scales within the Eastern Pacific plays a strong role in the conditions that impact the growing season. As a result of changes in climate and climate variability, the benefit to agriculture during this period produces mixed results for both regions. This work will evaluate the growing season conditions using indexes that combine growing season temperature and precipitation such as the hydrothermal coefficient (HTC) and the bioclimatic potential (BCP). Also, the interannual variability of these indexes in both regions was examined. In the Belgorod region, the increase in temperature combined with little change in precipitation produced mixed results in interpreting these indexes. This was accompanied by more variable conditions as revealed by these indexes in the early twenty-first century. In the Missouri region, there was little trend in either index over the time period and the tendency was toward less climatic variability in the HTC and BCP.

The character of the atmospheric general circulation during summer-season droughts over Eastern Europe/Western Russia and North America during the late twentieth and early twenty first century is examined here. A criterion to examine atmospheric drought events that encompassed the summer season (an important part of the growing season) was used to determine which years were driest, using precipitation, evaporation, and areal coverage. The relationship between drought and the character of the atmosphere, using the Dzerzeevsky weather and climatic classification scheme, atmospheric blocking, teleconnections, and information entropy, was used to study the atmospheric dynamics. The National Centers for Environmental Prediction (NCEP) re-analyses dataset archived at the National Center for Atmospheric Research (NCAR) in Boulder, CO, USA, is used to examine the synoptic character and calculate the dynamic quantities for these dry events. The results demonstrate that extreme droughts over North America are associated with a long warm and dry period of weather and the development of a moderate ridge over the Central USA driven by surface processes. These were more common in the late 20th century. Extreme droughts over Eastern Europe and Western Russia are driven by the occurrence of prolonged blocking episodes, as well as surface processes, and have become more common during the 21st century.