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Title: RELATIONS BETWEEN ALBEDOS AND EMISSIVITIES FROM MODIS AND ASTER DATA OVER NORTH AFRICAN DESERT

Author
item ZHOU, L. - GEORGIA INST. OF TECH
item DICKINSON, R. - GEORGIA INST. OF TECH
item TIAN, Y. - GEORGIA INST. OF TECH
item OGAWA, K. - HITACHI LTD
item Schmugge, Thomas
item JIN, M. - UNIV. OF MARYLAND
item TSVETSINKAYA, E. - BOSTON UNIV.

Submitted to: Geophysical Research Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/13/2003
Publication Date: 4/10/2003
Citation: Zhou, L., Dickinson, R.E., Tian, Y., Ogawa, K., Schmugge, T., Jin, M., Tsvetsinkaya, E. 2003. Relations between albedos and emissivities from MODIS and ASTER data over North African Desert. Geophysical Research Letters. 30(20):2026-2031.

Interpretive Summary: The thermal emission from the land surface is important in quantifying the surface radiation balance. The emission from the land is controlled by its emissivity. This paper studies the relationships between the broadband emissivity obtained using data from the Advance Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on board NASA's Terra satellite, the surface reflectivity derived from MODerate resolution Imaging Spectroradiometer (MODIS) sensor on the same spacecraft and the soil/surface type. The results show that there is a strong relation between soil type and both emissivity and reflectivity. These data are for a desert region in North African where the spatial variation of the land surface emissivity and reflectivity is very large. These results will be important for atmospheric/climate modelers who need to quantify the radiative energy balance at the land surface.

Technical Abstract: This paper analyzes relations among MODerate resolution Imaging Spectroradiometer (MODIS) surface albedos, Advanced Spaceborne Thermal Emission and Reflection Radiometer(ASTER) broadband (3-14 micrometer) emissivities, and a soil taxonomy map over the arid areas of Algeria, Libya, and Tunisia in North Africa at 30 second and 2 minute spatial resolutions. The MODIS albedo data are from 7 spectral bands and 3 broadbands during dust-free seasons and the emissivity data are derived from a linear combination of the waveband emissivities of the ASTER five thermal infrared channels. Both albedo and emissivity data in the study region show similar considerable spatial variability, larger than assumed by most climate models, and such variability is related to the surface types (sands, rock, and soil orders). Emissivity exhibits statistically significant correlations with albedos at both broadbands and spectral near-infrared bands and decreases linearly with albedo over bare soils. Albedo and emissivity are more strongly correlated with each other than either is to the surface types. This paper provides guidance for the possible inclusion of such correlation to specify albedo and emissivity in climate models.