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Title: ESTIMATION OF LAND SURFACE WINDOW (8-12 MICROMETER) EMISSIVITY FROM MULTISPECTRAL THERMAL INFRARED REMOTE SENSING - A CASE STUDY IN A PART OF SAHARA DESERT

Author
item OGAWA, KENTA - HITACHI LTD
item Schmugge, Thomas
item JACOB, FREDERIC - PRIVATE CONSULTANT

Submitted to: Geophysical Research Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/18/2002
Publication Date: N/A
Citation: N/A

Interpretive Summary: The atmosphere is relatively transparent in the 8 - 12 micrometer wavelength region, therefore thermal emission from the land surface can readily escape to space. The emission from the land is controlled by its emissivity. This paper presents some first results on the mapping of the emissivity in this wavelength region using data from the Advance Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on board NASA's Terra satellite. These data are for a desert region in North Africa where the spatial variation of the land surface is very large. These results will be important for atmospheric modellers who need to the radiative energy balance at the land surface.

Technical Abstract: Land surface window emissivity is an important parameter for estimating the longwave radiative budget. This study focuses on estimating the window (8-12 micrometer) emissivity from the waveband emissivities of the five thermal infrared channels of the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER). ASTER data along with Temperature-Emissivity Separation algorithm allows us to estimate surface channel emissivities with 90 m spatial resolution globally. Multiple regression was used to relate window emissivity to the five ASTER emissivities. This regression was developed using spectral libraries. Its residual error was smaller than 0.005 (RMSE) for values ranging between 0.81 and 1.00. We applied this regression to ASTER emissivities extracted from data acquired in 2001 and 2002 over a 240 x 1200 km area in a desert region of North Africa. A comparison against a classification based emissivity map showed significant differences ranging between -0.08 and +0.06.