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Upper‐level steering flow and continental anticyclones on the central Gulf Coast of the United States
Author(s) -
Rohli Robert V.,
Henderson Keith G.
Publication year - 1998
Publication title -
international journal of climatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.58
H-Index - 166
eISSN - 1097-0088
pISSN - 0899-8418
DOI - 10.1002/(sici)1097-0088(199807)18:9<935::aid-joc299>3.0.co;2-u
Subject(s) - anticyclone , climatology , zonal flow (plasma) , circumpolar star , forcing (mathematics) , subtropics , environmental science , geology , siberian high , north atlantic oscillation , zonal and meridional , flow (mathematics) , atmospheric circulation , oceanography , geography , physics , plasma , geometry , mathematics , archaeology , quantum mechanics , fishery , east asia , china , tokamak , biology
In a previous paper, trends in weather types dominated by continental anticyclones over the central Gulf Coast of the United States were analyzed. These events were found to be decreasing in frequency from 1961 to 1989. Magnitudes of some individual surface atmospheric variables during these events also changed significantly over this period even though the air masses represented did not change significantly. In this paper, the geography of 500 hPa height variability and steering flow patterns are examined in periods preceding such events in New Orleans in order to explain the forcing mechanisms that may be producing the observed frequency and intensity changes. Results indicate that the meridional gradient of atmospheric mass between the subtropics and extratropics may have increased over time, and consequently the increased zonal flow may have contributed to the relative paucity of continental anticyclone days in recent years. The zonality/meridionality of the flow and the extent of the circumpolar vortex over the region both appear to be related to the observed frequency shift. Furthermore, variability in the 500 hPa flow appears to be linked to the surface weather variability that was previously observed. These results are important in identifying the degree of scale interaction between upper‐level, hemispheric‐scale flow and local‐ to regional‐scale surface weather patterns. © 1998 Royal Meteorological Society