A contribution to Antarctic climate study : Variability of surface melting between 1979 and 1999 from microwave remote sensors. And parametrisation of the stable atmospheric boundary layer.

• Main Author: Torinesi, Olivier
• Other Authors: Laboratoire de glaciologie et géophysique de l'environnement (LGGE), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS), Université Joseph-Fourier - Grenoble I, Michel Fily
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2002
• Subjects: Antarctique; Télédétection; Micro-ondes; Température de brillance; Fonte de surface; Variabilité climatique; Modèle de la circulation générale de l'atmosphère; Paramétrisation; Couche limite atmosphérique; Stratification stable; Flux turbulents; [SDU.STU.GL]Sciences of the Universe [physics]/Earth Sciences/Glaciology; Antarctic; The Antarctic; Antarc*; Antarctique*; polar night
• Online Access: https://tel.archives-ouvertes.fr/tel-00755689; https://tel.archives-ouvertes.fr/tel-00755689/document; https://tel.archives-ouvertes.fr/tel-00755689/file/These-Torinesi-2002.pdf

In the first part of this report, partial summer melting of antarctic snow, which significantly affects the microwave emissivity of the surface, is identified and counted over 18 years in the 20-year period 1980-1999. To process the satellite data, an algorithm that adapts to the spatial and interannual variability of the mean brightness temperature of snow was developped. The cumulated product of the surface area affected by melting and the duration of the melting event, called Cumulative Melting Surface (CMS), is one of the three melt indices defined and discussed here. On average over the last 20 years, the Antarctic CMS has decreased by 1.8 ± 1 % year-l, a result which is consistent with a mean January cooling of the continent, recently identified by others from infrared satellite data. In addition, the interannual signature of the Antarctic Oscillation (AO), and possibly of the Southern Oscillation (ENSO), are found in the melt indices. Atmospheric general circulation models (AG CM) are still insufficiently advanced to adequately describe ail polar climate charateristics. In particular, the surface energy balance, and consequently snow melt, is incorrectly simulated by the AGCM LMDz. To improve this, a non local parametrisation of surface turbulent fluxes in highly stable and long-lived boundary layers (typical of the long antarctic polar night) is tested. The parametrisation accounts for vertical propagation of gravit y waves from the free troposphere, creating intermittent turbulence in the stable layer. Despite a high interannual climatic variability, the surface temperature and wind speed are generally better simulated on the continent, but a decoupling between the surface and the first vertical level appears near Vostok. Dans une première partie de ce travail, la fonte estivale partielle de la neige antarctique, qui affecte fortement l'émissivité micro-onde de la surface, est identifiée et comptabilisée au cours de 18 années sur la période 1980-1999. Pour cela, un algorithme de traitement des données ...