Study of microwave spectral signatures measured by remote sensing over the Antarctic ice sheet. Comparison with ground data and wlth a snow emissivity model.

• Main Author: Surdyk, Sylviane
• 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; Jean Pierre Benoist
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 1993
• Subjects: Télédétection; données de terrain; données SMMR; émissivité micro-onde; constante diélectrique; neige; modèles; [SDU.STU.GL]Sciences of the Universe [physics]/Earth Sciences/Glaciology; Antarctic; The Antarctic; Antarc*; Antarctique*; Ice Sheet
• Online Access: https://tel.archives-ouvertes.fr/tel-00765202; https://tel.archives-ouvertes.fr/tel-00765202/document; https://tel.archives-ouvertes.fr/tel-00765202/file/These-Surdyk-1993.pdf

Because of its great size, the Antarctic Ice Sheet represents a considerable fresh water resource. Furthermore, it interacts with the global climate and its old ice contains information on past climates. However, the sign of it mass balance is actually unknown. Microwave radiometers are valuable tools for studying the snow coyer because they provide useful data regardless of the weather, and because they penetrate the snow and give access to its characteristics from one to a few meters deep. The snow parameters (temperature, density and grain size) are linked to the climate parameters such as snow accumulation rate or temperature. Therefore, the objective is to retrieve the different snow characteristics from the microwave signatures. The satellite data that we used came from the Scanning Multichannel Microwave Radiometer (aboard the satellite Nimbus 7, 1978-86). As a first step, we compared ground data with the SMMR data. The polarization differences are affected by the stratification of snow (number and nature of layers); large polarization ratios correspond to strong stratification, mainly for the lower frequencies. The frequency gradients are linked to the grain sizes as determined from detailed stratigraphies; the larger the grain size, the smaller is the frequency gradient between 6.6 and 18 GHz. As a second step, we develop a microwave snow emissivity modal. The model is based on the solution of Maxwell's equations through strong fluctuation theory (Stogryn, 1986). An analytical solution is used where the snow is taken as uniform throughout its depth. * A numerical solution is required when snow characteristics change with depth. The snow is considered isothermal with horizontal stratification, isotropic inside each stratum, and with smooth interfaces. The model is used to study the sensitivity of snow density, snow grain size and stratification on the spectral signatures. Results are compared with observed signatures. Les études sur l'Antarctique sont motivées par l'interprétation des données que ...