Anthony R. Lupo1,*, Nina K. Kononova2, Inna G. Semenova3, and Maria G. Lebedeva4
Atmosphere 2021, 12,
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1 Atmospheric Science Program, School of Natural Resources, University of Missouri, Columbia, MO 65211, USA, [email protected]
2 Institute of Geography, Russian Academy of Sciences, Moscow 119017, Russian Federation.
3 Department of Military Training, Odessa State Environmental University, Odessa, Ukraine, 9 [email protected]
4 Department of Geography and Geoecology, Belgorod State University, Belgorod 308015, Russia; [email protected] 12
* Correspondence: [email protected]; Tel.: +1 573.489.8457
Abstract: 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.
Keywords: meteorological drought; agricultural drought; atmospheric circulation; elementary circulation mechanism (ECM); information entropy; atmospheric blocking