Role of the marine surface on the summer intraseasonal atmospheric circulation variability in the North Atlantic European region

• Main Author: Guemas, Virginie
• Other Authors: Laboratoire des Sciences du Climat et de l'Environnement Gif-sur-Yvette (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Groupe d'étude de l'atmosphère météorologique (CNRM-GAME), Institut national des sciences de l'Univers (INSU - CNRS)-Météo France-Centre National de la Recherche Scientifique (CNRS), Université Paul Sabatier - Toulouse III, David Salas (CNRM), Masa Kageyama (LSCE)
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2009
• Subjects: weather regimes; diurnal cycle; ocean-atmosphere interactions; ocean mixed layer; intraseasonal variability; régimes de temps; cycle diurne; interactions océan-atmosphère; couche de mélange océanique; variabilité intrasaisonnière; [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; North Atlantic; Sea ice
• Online Access: https://tel.archives-ouvertes.fr/tel-00451936; https://tel.archives-ouvertes.fr/tel-00451936/document; https://tel.archives-ouvertes.fr/tel-00451936/file/manuscript2.pdf

Cette thèse a été récompensée par le prix Adrien Gaussail 2010, prix décerné tous les deux ans par l'Académie des Sciences Inscriptions et Belles Lettres de Toulouse a un ouvrage scientifique. This PhD aims at assessing if the coupling of the atmosphere with the marine surface plays a role in the summer intraseasonal variability of the large-scale atmospheric circulation and if the marine surface can be a source of potential predictability for the atmosphere on these timescales. A second objective is to analyse the role of representing the ocean diurnal variations on the representation of the sea surface temperatures and the large-scale atmospheric circulation on longer timescales. To conduct this work, the CNRMOM1D 1-dimensional ocean model has been developped : the choice of parametrizations used in this model aims at optimizing the representation of physical processes dominating the evolution of Sea Surface Temperatures (SST) on diurnal to intraseasonal timescales. The results obtained from numerical simulations run with the ARPEGE-climat atmosphere model, forced or coupled with the CNRMOM1D ocean model, suggest that the SST anomalies induced by the large-scale atmospheric circulation produce a negative retroaction on the atmosphere on intraseasonal timescales : the coupling with the ocean surface in the North Atlantic European region reduces the persistence of the summer Atlantic Low, Blocking and NAO- weather regimes by about 1day which amounts to about 15% of their mean persistence. Using CNRMOM1D ocean forced simulations, we show that the correction in daily mean SST induced by the representation of the ocean diurnal variations can reach 0.3°C to 0.5°C. This anomaly can persist about 15 to 40 days in the mid-latitudes, more than 60 in the Tropics. Furthermore, using coupled simulations with the ARPEGE-climat atmosphere model, we show that the ocean diurnal variability can modify the summer mean state by a reduction of the SST meridional gradient, a reduction in sea ice extent, a anomaly in large-scale ...