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
SAINT MARTIN D'HERES Cedex, FRANCE
(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
MARTIN D'HERES, FRANCE
ABSTRACT
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
1 - INTRODUCTION
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
investigation.
2 - DATA DESCRIPTION
Three experiments were undertaken in the last 2 years. Data are summarized in Table 1 and more precisely
described in this chapter.
Date
Airborne
Sensor
Satellite
In situ
measurements
24 April 1992
NO
Landsat TM
7 sites: 1, 3, 6, 7,
8, 10, 11
