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United States Department of Agriculture

Agricultural Research Service

Title: Observation of Surface Emissivity for Arid Lands

Authors
item Schmugge, Thomas
item French, Andrew
item Ritchie, Jerry
item Rango, Albert

Submitted to: European Geophysical Society Meeting
Publication Type: Abstract Only
Publication Acceptance Date: March 2, 2000
Publication Date: April 24, 2000

Technical Abstract: 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 observations it is possible to estimate the spectral emissivity variation for these surfaces. The data we will present is from the Thermal Infrared Multispectral Scanner (TIMS) instrument which has six channels in the 8- to 12-micron region from flights over the Jornada Experimental Range in New Mexico. The Jornada site is typical of a desert grassland where the main vegetation components are grass and shrubs. The approach is to use the Temperature Emissivity Separation algorithm to extract the temperature and six emissivities from the six channels of TIMS data. The algorithm makes use of an empirical relation between the range of observed emissivities and their minimum value. Data were obtained at 2- and 4-meter resolutions during the summer of 1997, and the results are in quantitative agreement with laboratory measurements of the emissivity for the quartz rich soils of the site with values < 0.8 for the 8- to 9-micron channels. For the longest wavelength channel, little spatial variation was observed with values of 0.96 +/ 0.005 over large areas.

Last Modified: 10/21/2014