Accueil > Actualités > Séminaires > Séminaire de Gloria Rea


Titre : Multi‐decadal changes and predictions over the Southern Hemisphere Polar region: role of the stratospheric representation in CMIP5 models
Nom du conférencier : Gloria Rea
Son affiliation : Department of Environmental Sciences, ”Parthenope” University of Naples, Naples, Italy
Laboratoire organisateur : LOCEAN
Date et heure : 05-04-2016 11h00
Lieu : UPMC - 4 place Jussieu - Paris 5e - salle de réunion LOCEAN, tour 45/55, 4eme étage
Résumé :

In the last decades, the strong stratospheric ozone hole over Antarctica has led to a long‐term lower stratospheric cooling that seasonally superimposes to the GHG cooling, affecting summertime circulation from the stratosphere to the surface of the Southern Hemisphere (SH). In the stratosphere, the ozone‐induced cooling westerly accelerates winds and delays the polar vortex break over long‐term scales; in the troposphere, this implies a poleward shift of the mid‐latitude jet and projects onto the positive phase of the Southern Annular Mode (SAM) at the surface. The projection of stratospheric trends onto the surface affects also oceanic circulation and temperature by variations in wind stress at the ocean surface and in the oceanic Ekman transport. The SAM positive phase projects onto Sea Surface Temperature (SST) colder anomalies around most of Antarctica and warmer anomalies around the west side of Antarctic Peninsula and at mid‐high latitudes. We demonstrate that a proper representation of the stratospheric processes in climate models is the key ingredient to fully capture multi‐decadal climate changes in the SH and to make more reliable future predictions. To do this, we  perform a multi‐model analysis assessing to which extent a limited representation of stratospheric processes in the Coupled Intercomparison Project Phase 5 (CMIP5) models leads to biases in the representation of simulated SH stratospheric, tropospheric and surface changes on multi‐decadal time scales. All these same changes are analyzed also for future scenarios with projected increase of GHGs and ozone recovery. Finally, we investigate also the relationship between the SAM positive phase and the SST summertime trends for the different model classifications.