Atmospheric and upper ocean environments of Southern Ocean polar mesocyclones in the transition season months and associations with teleconnections

Chantal Claud, Andrew Mark Carleton, Bertrand Duchiron, Pascal Terray

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

Over middle and higher latitudes of the Southern Hemisphere, intense mesoscale cyclonic vortices that develop in cold-air outbreaks (cold-air mesocyclones) occur frequently during transition season months. In this study, previously published mesocyclone inventories for March-April and October-November are compared to atmospheric and upper ocean variables pertinent to mesocyclogenesis, as provided by reanalyses. This procedure allows the determination of the large-scale environments favorable for mesocyclone occurrence: low midtropospheric temperatures, greater sea ice extent, and large positive differences in the sea surface temperature minus low-altitude air temperature, the latter coinciding with enhanced low-level winds having a southerly component. We then evaluate the associations between polar mesocyclone formation and dominant patterns of low-frequency variability in the atmospheric circulation: the El Niño-Southern Oscillation (ENSO), the Southern Annular Mode (SAM), and the Trans-Polar Index (TPI). Our results suggest that in spring, the intrahemispheric variability in mesocyclogenesis is dominated by ENSO. In autumn, the influences of ENSO, SAM, and TPI on mesocyclone activity are about equal, although the response differs regionally. Moreover, teleconnections' effects on mesocyclone activity are somewhat reduced compared to that in spring. In both seasons, the phase of the semiannual oscillation modulates the associations with mesocyclones by influencing the latitude of the circumpolar trough and the amount of cyclonic activity over the Southern Ocean. These associations likely result from the displacement of the storm track between opposite phases of a given teleconnection and its position relative to the sea ice edge.

Original languageEnglish (US)
Article numberD23104
JournalJournal of Geophysical Research Atmospheres
Volume114
Issue number23
DOIs
StatePublished - Jan 1 2009

Fingerprint

Southern Oscillation
teleconnection
upper ocean
oscillation
oceans
Sea ice
sea ice
cold air
air
ocean
Air
semiannual oscillation
atmospheric circulation
ice
autumn
storm track
sea surface temperature
low altitude
Southern Hemisphere
troughs

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Forestry
  • Oceanography
  • Aquatic Science
  • Ecology
  • Water Science and Technology
  • Soil Science
  • Geochemistry and Petrology
  • Earth-Surface Processes
  • Atmospheric Science
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Palaeontology

Cite this

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title = "Atmospheric and upper ocean environments of Southern Ocean polar mesocyclones in the transition season months and associations with teleconnections",
abstract = "Over middle and higher latitudes of the Southern Hemisphere, intense mesoscale cyclonic vortices that develop in cold-air outbreaks (cold-air mesocyclones) occur frequently during transition season months. In this study, previously published mesocyclone inventories for March-April and October-November are compared to atmospheric and upper ocean variables pertinent to mesocyclogenesis, as provided by reanalyses. This procedure allows the determination of the large-scale environments favorable for mesocyclone occurrence: low midtropospheric temperatures, greater sea ice extent, and large positive differences in the sea surface temperature minus low-altitude air temperature, the latter coinciding with enhanced low-level winds having a southerly component. We then evaluate the associations between polar mesocyclone formation and dominant patterns of low-frequency variability in the atmospheric circulation: the El Ni{\~n}o-Southern Oscillation (ENSO), the Southern Annular Mode (SAM), and the Trans-Polar Index (TPI). Our results suggest that in spring, the intrahemispheric variability in mesocyclogenesis is dominated by ENSO. In autumn, the influences of ENSO, SAM, and TPI on mesocyclone activity are about equal, although the response differs regionally. Moreover, teleconnections' effects on mesocyclone activity are somewhat reduced compared to that in spring. In both seasons, the phase of the semiannual oscillation modulates the associations with mesocyclones by influencing the latitude of the circumpolar trough and the amount of cyclonic activity over the Southern Ocean. These associations likely result from the displacement of the storm track between opposite phases of a given teleconnection and its position relative to the sea ice edge.",
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Atmospheric and upper ocean environments of Southern Ocean polar mesocyclones in the transition season months and associations with teleconnections. / Claud, Chantal; Carleton, Andrew Mark; Duchiron, Bertrand; Terray, Pascal.

In: Journal of Geophysical Research Atmospheres, Vol. 114, No. 23, D23104, 01.01.2009.

Research output: Contribution to journalArticle

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AB - Over middle and higher latitudes of the Southern Hemisphere, intense mesoscale cyclonic vortices that develop in cold-air outbreaks (cold-air mesocyclones) occur frequently during transition season months. In this study, previously published mesocyclone inventories for March-April and October-November are compared to atmospheric and upper ocean variables pertinent to mesocyclogenesis, as provided by reanalyses. This procedure allows the determination of the large-scale environments favorable for mesocyclone occurrence: low midtropospheric temperatures, greater sea ice extent, and large positive differences in the sea surface temperature minus low-altitude air temperature, the latter coinciding with enhanced low-level winds having a southerly component. We then evaluate the associations between polar mesocyclone formation and dominant patterns of low-frequency variability in the atmospheric circulation: the El Niño-Southern Oscillation (ENSO), the Southern Annular Mode (SAM), and the Trans-Polar Index (TPI). Our results suggest that in spring, the intrahemispheric variability in mesocyclogenesis is dominated by ENSO. In autumn, the influences of ENSO, SAM, and TPI on mesocyclone activity are about equal, although the response differs regionally. Moreover, teleconnections' effects on mesocyclone activity are somewhat reduced compared to that in spring. In both seasons, the phase of the semiannual oscillation modulates the associations with mesocyclones by influencing the latitude of the circumpolar trough and the amount of cyclonic activity over the Southern Ocean. These associations likely result from the displacement of the storm track between opposite phases of a given teleconnection and its position relative to the sea ice edge.

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