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dépendance of the polarized reflectance around 140 degrees scattering angle or, more
generally, scattering angles for rainbows.
5-CONCLUSIONS
The photopolarimetric observations made by the POLDER instrument show that polarized
reflectance may be used also for cloud altimetry. They indicate that snow/ice and clouds
have very similar spectral and bidirectional properties, making it difficult, even impossible
to use only those properties to detect the presence of clouds over snow-ice surfaces. The
polarization state of the reflected and scattered light by the two types of targets, in the
contrary, exhibits distinct characteristics at scattering angles for rainbows, when the
clouds contain water droplets. We conclude that polarization measurements provide an
efficient means to screen liquid water clouds over snow/ice surfaces.
AKNOWLEDGEMENTS
This work has been supported in part by the National Aeronautics and Space administration
under grant NAGQ-2774 to Robert Frouin
REFERENCES
Deschamps P.Y , F.M Bréon, A Bricaud, J.C Buriez, J.L Deuzé, M Herman, M. Leroy, A Podaire
and G Sèze, 1992. The POLDER mission: instrument characteristics and scientific objectives.
Submitted to IEEE Trans. Geosci. Remote Sensing, in press.
Coffeen, D.L. and J.E.Hansen, 1972. Airborne infrared polarimetry. Proc. of the eighth
international symposium of remote sensing of environment. 2-6 Oct. 1972.
Deirmendjian,1969. Electromagnetic scattering on spherical polydispersions. American Elsevier
Publishing Company, Inc New York.
Deschamps, P.Y, M Herman, A Podaire, M Leroy, M. Laporte and P Vermande, 1990. A spatial
instrument for the observation of polarization and directionality of Earth reflectances: POLDER,
Proc. 1GARSS' 90, Washington D.C., 1990.
Deuzé, J.L., C Devaux, M Herman, R Santer, J.Y Balois, L Gonzalez, P Lecomte and C
Verwaerde, 1989. Photopolarimetric observations of aerosols and clouds from balloon. Remote
Sens. Environ., 29, 93-109.
Egan W.G, 1985:" Airborne observations of polarization and photometry of terrestrial surfaces".
Nineteenth International Symposium on Remote Sensing of Environment, Ann Arobor,
Michigan, October 1985.
Goloub P, 1992 "Modèle radiométrique du polarimètre imageur grand champ POLDER.
Analyses préliminaires des observations en lumière polarisée", Thèse d'Université, n° 1003,
Université des Sciences et Technologies de Lille.
Goloub P, M Herman, JL Deuzé, R Frouin 1992 " Contrast between polarization of snow/ice
and clouds". Special issue of Antarctic Journal of United States, p 199-202.
Goloub P, JL Deuzé, M Herman, Y Fouquart, 1993 " Analysis of the POLDER polarization
measurements performed over cloud covers IEEE Trans. Geosci. Remote Sensing, in press.
Hansen J.E. and L.D Travis, 1974. Light scattering in planetary atmospheres. Space Science
Reviews, 16, 527-610.
Roger JC, R Santer , M Herman, JL Deuzé, 1993, " Polarization of the solar light scattered by the
Earth-Athmosphere system as observed from the US shuttle", Rem. Sensing.of Environment. In
press.
