ASTER observations of surface temperature and emissivity over New Mexico test sites

TitleASTER observations of surface temperature and emissivity over New Mexico test sites
Publication TypeConference Paper
Year of Publication2003
AuthorsSchmugge T.J., Ogawa K., French A.N., Hsu A.Y., Ritchie J., Rango A.
Conference NameFall 2003 Meeting, American Geophysical Union
Date PublishedDecember 8-12, 2
Conference LocationSan Francisco, CA
ARIS Log Number159709
AbstractThe multispectral thermal infrared data obtained from the Advanced Spaceborne Thermal Emission and Reflection (ASTER) radiometer on NASA's Terra satellite have been of good quality and provide a unique new tool for studying the land surface. ASTER has five bands in the 8-12 micrometer waveband with 90 m spatial resolution; when the data are combined with the Temperature Emissivity Separation (TES) algorithm, the surface emissivity over this wavelength region can be determined along with the surface temperature. This paper will present some quantitative emissivity and temperature results obtained over test sites in southern New Mexico (the Jornada Experimental Range and the White Sands National Monument). These results are compared with ground observations. The Jornada site is typical of a desert grassland where the main vegetation components are grass and shrubs with a large fraction of exposed soil, while the White Sands site is mainly dunes of gypsum sand which provides a good relatively homogenous emissivity target with an interesting spectral signature. More than two dozen ASTER scenes over these New Mexico test sites have been acquired since the launch of Terra in December 1999. There were simultaneous field campaigns in May of 2000-2003 and September/October 2001 and 2002. Also, ASTER (MODIS-ASTER airborne simulator) coverage was obtained for several of the dates. The ASTER surface brightness temperatures compare very well with those obtained on the ground. The results appear to be in good quantitative agreement with laboratory measurements of the emissivity for the quartz rich soils of the Jornada with values less than 0.85 for the 8-9 micrometer channels. For the longest wavelength channels little spatial variation of the emissivity was observed with values of 0.96 +/- 0.005 over large areas. Emissivity values from the ASTER data for the gypsum at White Sands were in good agreement with values calculated from the lab spectra for gypsum and with each other. Gypsum has a strong emissivity minimum centered on the ASTER 8.63 micrometer band , and the satellite results for this band agree within 0.01 of the value calculated from the laboratory spectra. The extension of these results to mapping emissivity over large areas will be presented in the form of an emissivity map for the deserts of North Africa.