Changes in the Atmospheric Circulation Conditions and Regional Climatic Characteristics in Two Remote Regions Since the Mid-20th Century

Abstract

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.

Changes in the Dynamics of the Northern Hemisphere Atmospheric Circulation and the Relationship to Surface Temperature in the 20th and 21st Centuries

“…Further, in [1] the authors discussed the temporal and spatial variations in DKV46 ECM scheme as consistent with earlier studies of NH flows [14][15][16][17][18] (among others) that suggests the NH flow vacillates between two or more quasi-stable states. Many studies (e.g., [19][20][21]) also demonstrate that such flow regime behavior occurs independently in each of the major NH ocean basins.…”

“…For the analysis of global of hemispheric atmospheric flow regimes, many teleconnection or blocking indexes have been developed and are currently used (e.g., [1,2]) both operationally and in research. The study of atmospheric circulation and teleconnections in the Northern Hemisphere (NH) began in the 1940s (e.g., [3,4]).…”

“…Among the first of these was a classification system developed for the categorization of extratropical atmospheric circulation patterns in the NH published in [5] (hereafter called DKV46). Briefly, this system classifies NH flows based on whether the NH flow is more zonal or meridional, as well as the number and geographical position of waves along the polar front or jet stream [1,6]. The original work used 13 different categorizations called Elementary Circulation Mechanisms (ECMs) [6] that were grouped into four basic zonal and meridional types ( [1,6]).…”

“…Briefly, this system classifies NH flows based on whether the NH flow is more zonal or meridional, as well as the number and geographical position of waves along the polar front or jet stream [1,6]. The original work used 13 different categorizations called Elementary Circulation Mechanisms (ECMs) [6] that were grouped into four basic zonal and meridional types ( [1,6]). Then, recent research [1] showed the correlation of certain ECMs to NH teleconnections such as the Arctic Oscillation (AO) or the North Atlantic Oscillation (NAO).…”

“…The original work used 13 different categorizations called Elementary Circulation Mechanisms (ECMs) [6] that were grouped into four basic zonal and meridional types ( [1,6]). Then, recent research [1] showed the correlation of certain ECMs to NH teleconnections such as the Arctic Oscillation (AO) or the North Atlantic Oscillation (NAO).…”