This study examines the long-term fluctuations in the Northern Hemisphere (NH) and global atmospheric circulation, teleconnections, including blocking, and surface temperature over the period 1899–2018. The teleconnection and blocking data were available from the mid-20th century. The classification of the global atmospheric circulation was developed from an early subjective categorization of atmospheric circulation conditions for the NH that considered the number, location, and amplitude of waves on the jet stream for frequently occurring circulation patterns. This work updated earlier studies that identified three circulation epochs based on the predominance of one of four different flow types that were grouped primarily based on whether the flow was zonal or meridional. This work noted a significant correlation between the early 21st century flow change toward the occurrence of more meridional flows and the increase in the occurrence of blocking as well as changes in the teleconnection indexes. The early 21st century was associated with a distinct change in the Northern Hemisphere flow entropy as measured using Information or Shannon Entropy, a change that was shown to be statistically significant. Additionally, this demonstrated that this quantity has utility as a dynamic diagnostic tool in atmospheric science. Finally, a comparison of these flow regimes to the 20th and 21st century variations in surface temperature were considered here. The global average annual surface temperature variations correlated strongly to fluctuations in the predominant atmospheric circulation type.

The regional features of the spatial distribution of extensive severe atmospheric droughts during the vegetation season in the south of the East European Plain at the beginning of the 21st century were studied according to the data on the Palmer Drought Severity Index. The circulation conditions for the formation of droughts were analyzed, and the characteristics and some regularities of blocking episodes were revealed. It was shown that the boundaries of severe droughts are in good agreement with the domains of negative extremes of the satellite vegetation index, which are observed in July and August.

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.