Full text: Mesures physiques et signatures en télédétection

Airborne and spaceborne multisensor remote sensing of snow 
with in situ measurements in the Alps. Preliminary results. 
B. Bourdelles (I), J.P. Dedieu (2), Y. Durand (3), S. Farley (2), M. Fily (1), Y. Page (1), C. Sergent (3), 
C. Roche (2), S. Vincent (2) 
(1) LGGE: Laboratoire de Glaciologie et de Géophysique de l'Environnement, CNRS, UJF, B.P. 96, 38402 
(2) LAMA: Laboratoire de la Montagne Alpine, IGA, 31 Rue Maurice Gignoux, 38030 GRENOBLE 
Cedex, FRANCE 
(3) CEN: Centre d'Etudes de la Neige, CNRM, Météo-France, 1441 Rue de la Piscine, 38406 SAINT 
Three experiments were carried on in the French Alps to study the reflectance of the snow in the solar 
spectrum. Satellite (Landsat, SPOT) and airborne (radiometer, spectrometer) data were acquired 
simultaneously with ground truth measurements (temperature, grain size) at many different sites. The 
measurements are compared to model results: snow bidirectional reflectance model and snow metamorphism 
model. The data and their processing are described. Finally two examples are given about the results on 
temperature determination and about the effect of grain size on the reflectance. 
KEY WORDS: Remote sensing, snow, solar spectrum, satellite 
In the visible part of the solar spectrum the snow reflectance is mainly dependent on its pollution; in the 
near infrared it is dependent on the snow grain geometry: shape and size (Warren, 1982). Our objective is 
to better understand these relations with two different goals. First, for climatological studies or for 
avalanche forecasting, we need to parameterise the snow albedo from its characteristics in order to compute 
the radiative balance at the surface (Brun et al., 1989). In the other hand we would like to know if it is 
possible to measure snow characteristics from remote sensing data which could be used to validate snow 
metamorphism model or to get some information on the snow mantle in remote areas such as the polar ice 
sheets (Bourdelles and Fily, 1993). 
For these goals many experiments were carried out in the French Alps with simultaneous remote sensing 
and ground truth data at different locations. In the following paper we describe the data, their processing 
and the theoretical tools that we use: snow metamorphism and snow reflectance models. Some preliminary 
results are given on the comparison between models and measurements, many other studies are still under 
Three experiments were undertaken in the last 2 years. Data are summarized in Table 1 and more precisely 
described in this chapter. 
In situ 
24 April 1992 
Landsat TM 
7 sites: 1, 3, 6, 7, 
8, 10, 11

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