Stationary Atmospheric Responses to an Idealized Sea Surface Temperature Anomaly in the Southern Ocean.

• Published in: Journal of Climate
• Main Authors: Maze, Guillaume, D'Andrea, Fabio, Colin De Verdiere, Alain, Klein, Patrice
• Other Authors: Laboratoire de physique des océans (LPO), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), 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)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2011
• Subjects: Quasigeostrophic models; Barotropic flows; Baroclinic flows; Atmosphere-ocean interaction; Southern Ocean; Sea surface temperature; [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography; Drake Passage; Pacific; Indian; South Pole; South pole
• Online Access: https://hal.archives-ouvertes.fr/hal-00650199; https://hal.archives-ouvertes.fr/hal-00650199/document; https://hal.archives-ouvertes.fr/hal-00650199/file/%5B15200442%20-%20Journal%20of%20Climate%5D%20Stationary%20Atmospheric%20Responses%20to%20an%20Idealized%20Sea%20Surface%20Temperature%20Anomaly%20in%20the%20Southern%20Ocean.pdf; https://doi.org/10.1175/2011JCLI3737.1

International audience The stationary atmospheric response to an idealized sea surface temperature anomaly (SSTA) is studied with a quasigeostrophic atmospheric model of the Southern Hemisphere. Sensitivity of the stationary response to the midlatitude SSTA location is determined and responses are decomposed on vertical modes. The SSTA almost directly forces baroclinic responses, inducing warm-air anomalies 40°-50° downstream, eastward, to the SSTA. These baroclinic responses arise from an equilibrium between the SSTA-induced anomalous vortex stretching and (i) advection by the quasi-stationary flow and (ii) dissipation by high-frequency eddies. The barotropic response consists of a midlatitude ridge (trough) and a South Pole trough (ridge) for SSTAs localized from the Drake Passage to the western Indian Ocean (from south of Australia to the center of the Pacific Ocean). This response can be further decomposed into (i) a zonally asymmetric component, a quasi-stationary wave train forced by a barotropic ridge downstream of the SSTA; and (ii) a zonal-mean component similar to a meridional shift of westerlies and hence a southern annular mode (SAM)-like pattern. The former component is phase locked with the SSTA position, while the latter has a phase that depends on the relative SSTA position with regard to the background quasi-stationary wave pattern. The study shows that the barotropic downstream ridge response is responsible for modifying the low-frequency eddy-mean flow interactions through relative vorticity fluxes and inducing the bipolar projection of the zonal-mean response.