The extreme atmospheric boundary layer over the Antarctic Plateau and its representation in climate models

• Main Author: Vignon, Etienne
• Other Authors: Institut des Géosciences de l’Environnement (IGE), Institut de Recherche pour le Développement (IRD)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes 2016-2019 (UGA 2016-2019 ), Université Grenoble Alpes, Christophe Genthon
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: HAL CCSD 2017
• Subjects: Stable atmospheric boundary layers; Antarctic Plateau; Climate modelling; Physical parametrizations; Couche limite atmosphérique stable; Plateau antarctique; Modélisation de l'atmosphère; Paramétrisation physiques; [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology; Antarctic; The Antarctic; Antarc*; Antarctique*; polar night
• Online Access: https://theses.hal.science/tel-01696807; https://theses.hal.science/tel-01696807/document; https://theses.hal.science/tel-01696807/file/VIGNON_2017_archivage.pdf

Observation of the Atmospheric Boundary Layers (ABL) above the Antarctic Plateau has revealed the strongest near-surface temperature stratifications on the Earth. A correct parametrization of the very stratified Antarctic ABLs in General Circulation Models (GCM) is critical since they exert a strongcontrol on the continental scale temperature inversion, on the coastal katabatic winds and subsequently on the Southern Hemisphere circulation. The previous Gewex Atmospheric Boundary Layer Studies (GABLS) highlighted that the parametrization of the very stratified, or very stable, ABLs isone of the most critical challenge in the atmospheric modelers community. Indeed, the nature of the mixing processes are not completely understood and the commonly used similarity laws, on which the model’s parametrization are usually based, are no longer valid. The aim of this PhD work is to evaluate and improve the modelling of the ABL over the Antarctic Plateau by the Laboratoire de Météorologie Dynamique-Zoom (LMDZ) GCM, the atmospheric component of the IPSL Earth System Model in preparation for the sixth Coupled Models Intercomparison Project. Before the model evaluation itself, an in-depth study of the dynamics of the atmospheric surface layer and of the stable ABL over the Antarctic Plateau was carried out from in situ measurements at Dome C. The analysis enabled the first estimations of the roughness length and of the surface fluxes during the polar night at this location as well as the characterization of very frequent occurences of near-surface moisture supersaturations with respect to ice. Investigation of meteorological measure-ments along a 45 m tower also revealed two distinct dynamical regimes of the stable ABL at this location. In particular, the relation between the near surface inversion amplitude and the wind speed takes a typical ’reversed S-shape’, suggesting a system obeing with an hysteresis. A further analysisshowed that this is a clear illustration of a general and robust feature of the stable ABL systems, ...