| || Remote Sensing of Snow in the Solar Spectrum: Experiments in the French Alps
Author : Fily, M.;Dedieu, J.P.;Durand, Y.;Sergent, C.
Source : Defence Science Journal ; Vol:50(2) ; 2000 ; pp 217-229
Subject : 551 Geology;550.3 Geophysics
Keywords : Snow metamorphism model;Landsat thematic mapper;CROCUS classification
Abstract : "Two experiments were performed in April and December 1992 in the French Alps using simultaneous remote sensing and ground truth data. Snow grain size and soot content of samples collected in the field were measured.The Landsat thematic mapper (TM) sensor was used because it has a good spatial resolution, a middle infrared channel which is sensitive to grain size and a thermal infrared channel. First the reflectance data were compared with the theoretical results obtained from a bidirectional reflectance model. Then, some remote sensing-derived snow parameters ere compared With the output of a snow metamorphism model (CROCUS), viz., lower elevation of the snowcover,the surface grain size and the surface temperature. A digital elevation model was used to obtain the local incidence angles and the elevation of each snow pixel. The pixels were then grouped according to CROCUS classification (range, elevation, slope, and orientation) and the mean snow characteristics for each class were compared with the CROCUS results. The lower limit of snow and the surface grain size derived from TM data were compared favourably with the model results. Larger differences were found for the temperature, because it varies rapidly and is very sensitive to shadowing by the surrounding mountains and also because its remote measurement is dependent on atmospheric conditions. "