Submitted to: Agronomie Agriculture Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/21/2002
Publication Date: N/A
Interpretive Summary: The longwave energy balance is controlled by the surface emissivity. It is this energy which is affected by the increase in carbon dioxide. A 1% change in emissivity produces a bigger change in the energy balance than the effects of increaded carbon dioxide. This magnitude of change is observable with the multispectral thermal infrared data being acquired by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER). ASTER is a sensor onboard the NASA Earth Observing System (EOS) Terra satellite launched in 1999. This paper demonstrates this capability with data acquired over the USDA/ARS Jornada Experimental Range in New Mexico.
Technical Abstract: Surface broadband emissivity in the thermal infrared (TIR) region is an important parameter for estimating the longwave surface energy balance. This study focuses on estimating the broadband emissivity of the land surface from the emissivities of the five spectral channels in TIR on the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER). ASTER is a sensor onboard the NASA Earth Observing System (EOS) Terra satellite launched in 1999, and has five channels in the TIR region (8-12 micrometer). Broadband emissivities (3-14 micrometer) were calculated using two spectral libraries, John Hopkins University Spectral Library (JHU Library) and MODIS UCSB (University of California, Santa Barbara) Emissivity Library (UCSB Library) for natural surfaces, such as, rocks, soils, vegetation, water, ice, and snow. Then, we assumed that the broadband emissivity can be expressed as a linear combination emissivities for the five ASTER channels. The linear empirical relation was calibrated using JHU Library and validated with the UCSB Library. The absolute error on the estimated broadband emissivity was less than 0.01 for 93 % over an emissivity range from 0.91 to 0.99 in validation. Finally, this calibrated regression was applied to emissivities computed from the data acquired with ASTER over the Jornada Experimental Range in New Mexico to produce a map of broadband emissivity for this area.