Submitted to: Remote Sensing in Hydrology Symposium
Publication Type: Proceedings
Publication Acceptance Date: July 15, 2000
Publication Date: N/A
Interpretive Summary: The emissivity of the surface has a major effect on the radiation energy balance at the earth's surface. Therefore, knowledge of the spatial variation of the surface emissivity is important for quantifying the radiation balance at the earth's surface. This paper presents preliminary results of a technique for observing this spatial variation. While these results were obtained using data from an aircraft sensor, it is extendable to data from satellite platforms and thus could be used on a global basis.
Knowledge of the surface emissivity is important for determining the radiation balance at the land surface. For heavily vegetated surfaces there is little problem since the emissivity is relatively uniform and close to one. For arid lands with sparse vegetation the problem is more difficult because the emissivity of the exposed soils and rocks is highly variable. With multispectral thermal infrared (TIR) observations it is possible to estimate the spectral emissivity variation for these surfaces. The data we will present is from the TIMS (Thermal Infrared Multispectral Scanner) instrument which has 6 channels in the 8 to 12 micron region. TIMS is a prototype of the TIR portion of the ASTER (Advanced Spaceborne Thermal Emission and Reflection radiometer) instrument to be flown on NASA's EOS-AM platform this coming summer. The Temperature Emissivity Separation algorithm developed for use with ASTER data is used to extract the temperature and 6 emissivities from the TIMS data. The algorithm makes use of the empirical relation between the range of observed emissivities and their minimum value. This approach was applied to the TIMS data acquired over the USDA/ARS Jornada Experimental Range in New Mexico which is typical of a desert grassland where there is a mixture of bare soil and vegetation. The resulting spectral emissivities are in qualitative agreement with laboratory measurements of the emissivity for the quartz rich soils of the site.