tailieunhanh - Albedo estimation from PolDER data

Multi-spectral and multi-directional data acquired during the ReSeDA experiment thanks to the airborne PolDER sensor were used to retrieve surface albedo over the experimental site, for 16 days over the year 1997. The data were available in four wave-bands (10 or 20 nm width) centered at 443 nm, 550 nm, 670 nm, and 865 nm. Zenith view angles ranged from 0 to 50 o. This study aimed at evaluate a procedure based on the use of multi-directional and multi-spectral information to retrieve surface albedo. Multidirectional information was extracted thanks to BRDF kerneldriven models. We compared the performances of three models (Walthall, Roujean and MRPV) in the four PolDER channels. The spectrally integrated value of the albedo was then derived from the of the hemispherical reflectance estimates in the four wave-bands, thanks to the linear regressions proposed by Weiss et al. (1999). 20 m resolution albedo maps were computed, and then compared to field measurements over several crop fields considering all days of the experiment. Results showed that PolDER retrievals overestimated ground measurements. This might be explained, at least partially, by inappropriate linear combinations used for the spectral extrapolation. | Albedo estimation from PolDER data F Jacob1 M. Weiss1 A. Olioso1 O. Hautecoeur2 C. Francois3 M. Leroy2 and C. Ottle 3 1INRA Bioclimatologie Domaine St Paul 84914 Avignon Cedex 9 France 2CESBio 18 avenue BP 2801 31041 Toulouse Cedex 4 France 3CETP IPSL CNRS 10-12 avenue de l Europe 78140 Velizy France Camera-ready Copy for Physics and Chemistry of the Earth Manuscript-No. Offset requests to F. Jacob INRA-Bioclimatologie Domaine St Paul Site Agroparc 84914 Avignon Cedex 9 France Journal Physics and Chemistry of the Earth MS No. First author Jacob 1 Albedo estimation from PolDER data F. Jacob1 M. Weiss1 A. Olioso1 O. Hautecoeur2 C. Francois3 M. Leroy2 and C. Ottle3 1INRA Bioclimatologie Domaine St Paul 84914 Avignon Cedex 9 France 2CESBio 18 avenue BP 2801 31041 Toulouse Cedex 4 France 3CETP IPSL CNRS 10-12 avenue de l Europe 78140 Velizy France Received - Accepted Abstract. Multi-spectral and multi-directional data acquired during the ReSeDA experiment thanks to the airborne PolDER sensor were used to retrieve surface albedo over the experimental site for 16 days over the year 1997. The data were available in four wave-bands 10 or 20 nm width centered at 443 nm 550 nm 670 nm and 865 nm. Zenith view angles ranged from 0 to 50 o. This study aimed at evaluate a procedure based on the use of multi-directional and multi-spectral information to retrieve surface albedo. Multidirectional information was extracted thanks to BRDF kernel-driven models. We compared the performances of three models Walthall Roujean and MRPV in the four PolDER channels. The spectrally integrated value of the albedo was then derived from the of the hemispherical reflectance estimates in the four wave-bands thanks to the linear regressions proposed by Weiss et al. 1999 . 20 m resolution albedo maps were computed and then compared to field measurements over several crop fields considering all days of the experiment. Results showed that PolDER retrievals overestimated ground .

• Năng lượng
• Albedo estimation
• Albedo estimation from PolDER data
• Multi directional
• Multi spectral information
• The four PolDER channels