Presentation on theme: "The retrieval of snow properties from space: theory and applications A. A. Kokhanovsky 1, M. Tedesco 2,3, G. Heygster 1, M. Schreier 1, E. P. Zege 4 1)University."— Presentation transcript:
The retrieval of snow properties from space: theory and applications A. A. Kokhanovsky 1, M. Tedesco 2,3, G. Heygster 1, M. Schreier 1, E. P. Zege 4 1)University of Bremen, Bremen, Germany 2)University of Maryland, Baltimore County, USA 3)NASA – Goddard Space Flight Center, Maryland, USA 4)Institute of Physics, Minsk, Belarus firstname.lastname@example.org
Introduction A new snow retrieval algorithm that makes use of visible and near-infrared measurements in which snow is modeled as a semi-infinite weakly absorbing medium is developed The shape of grains is accounted for by means of a fractal snow grain model The technique is applied to study the changes of snow properties before and just after snow fall in Colorado as seen by two MODIS sensors on TERRA and AQUA satellites The snow grain size and snow albedo have been retrieved from AATSR onboard ENVISAT data over Greenland Preliminary comparisons with ground measurements have been performed
3. Snow radiative transfer model - a=1.247, b = 1.186 and c= 5.157 - the function p is the snow grain phase function Snow spectral reflectivity R 0 = Reflectivity of a semi-infinite snow layer at zero absorption Escape function Kokhanovsky and Zege, 2004; Appl. Optics Kokhanovsky, 2006; Optics Letters (methane adsorption; Domine et al., 2006)
3. Snow radiative transfer model: albedo determination Reflectivity: Albedo:
3. Snow radiative transfer model grain size d spectral snow albedo r
4. Validation: Hokkaido Solar zenith angle=54deg
Observations and future work A new approach is to be developed (A. Lyasputin, UMBC/NASA; von Hoyningen-Huene, University of Bremen) for simultaneous retrieval of AOT and surface BRDF. This will improve MODIS snow BRDF product. The cloud mask must be improved. A comprehensive validation and calibration campaign is needed. This will be performed using measurements in Greenland (M. Tedesco, PI of the Proposal submitted to NASA NNH06ZDA001N-IPY).