Etude théorique et expérimentale de la réflectance de la neige sur le spectre solaire : application à la télédétection

• Main Author: Leroux, Catherine
• Other Authors: Laboratoire d’Optique Atmosphérique - UMR 8518 (LOA), Institut national des sciences de l'Univers (INSU - CNRS)-Université de Lille-Centre National de la Recherche Scientifique (CNRS), Université des Sciences et Technologie de Lille - Lille I, J.Lenoble; Michel Fily; C.Sergent
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 1996
• Subjects: reflectance neige; modélisation; études expérimentales; télédétection; [SDU.STU.GL]Sciences of the Universe [physics]/Earth Sciences/Glaciology; Antarctic; South Pole; The Antarctic; Antarc*; Antarctica; Ice Sheet; South pole
• Online Access: https://theses.hal.science/tel-00781634; https://theses.hal.science/tel-00781634/document; https://theses.hal.science/tel-00781634/file/These-Leroux-1996.pdf

Snow reflectance is an important climatic parameter and is a matter of interest for various fields of study such as glaciology, climatology, meteorology, avalanche forecasting . The main goal of this investigation is a theoretical and experimental study of snow reflectance from the visible to the near-infrared part of the solar spectrum. The originality of our study lies in three mean points: the introduction of hexagonal particles in order to model snow (Ray-tracing code), until then snow models were based on the use of sphericle particles (Mie theory), the polarization of the reflected light and the surface roughness effect on the reflectance which is due to Antarctica winds. The main part of this work is devoted to the modelling of snow optical properties from physical characteristics (size and shape of the snow grain) including snow contamination by carbon soot. The model is based on the radiative transfer theory by using the adding-doubling method and provides the radiance and the polarization of the reflected radiation. The limitations of the theory (shape of snow crystals in near infrared wavelengths) are became clear by comparisons with laboratory and ground based measurements. This study will serve as a basis for future remote sensing applications and for the interpretation of the future P.O.L.D.E.R. (POLarization and Directionality of Earth's Reflectance) sensor's data over the Antarctic Ice Sheet. For this pupose, a snow B.R.D.F. (Bidirectional Reflectance Distribution Function) model including surface roughness was developped. Reflectance ground measurements, performed at South Pole station, were made available to us and the comparisons with th model results are promising La réflectance de la neige est un paramètre climatique important qui suscite l'intérêt de plusieurs disciplines telles que la glaciologie, la climatologie, la météorologie, la prévision des risques d'avalanches. Le but de cette thèse est l'étude théorique et expérimentale de la réflectance de la neige sur la partie visible et ...