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

• Published in: Journal of Geophysical Research
• Main Authors: Claud, Chantal, Carleton, Andrew M., Duchiron, Bertrand, Terray, Pascal
• Other Authors: Laboratoire de Météorologie Dynamique (UMR 8539) (LMD), Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-École des Ponts ParisTech (ENPC)-École polytechnique (X)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Earth and Environmental Systems Institute PennState (EESI), Pennsylvania State University (Penn State), Penn State System-Penn State System, Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Muséum national d'Histoire naturelle (MNHN)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2009
• Subjects: [PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph]; [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph]; [SDU]Sciences of the Universe [physics]; Southern Ocean; Sea ice
• Online Access: https://hal.archives-ouvertes.fr/hal-00760025; https://hal.archives-ouvertes.fr/hal-00760025/document; https://hal.archives-ouvertes.fr/hal-00760025/file/2009JD011995.pdf; https://doi.org/10.1029/2009JD011995

International audience 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.