熱赤外多バンドリモートセンシングデータを用いた岩石表面のデザート・バーニッシュの厚さの評価

抄録

Thermal infrared (TIR) multi-spectral remote sensing has been successfully applied and become a useful tool in the fields of earth sciences. The objective of this study is to evaluate the spatial distribution of thickness of desert varnish (DV) coating on the arid land surface using TIR remote sensing data.
TIR emissivity spectra were measured on surface covered with DV coatings and freshly broken surface of rock samples collected in Cuprite, Nevada. The measured spectra of rock surface with DV coatings were low in contrast comparing with ones of broken surface, and they have the absorption features from 9.0 to 10.0μm due to the DV coatings. The silicified rocks have two emissivity minima in TIR region ; 8.25 μpm and 9.2μm. The depth of each minimum decreases as the relative thickness and amount of DV coating on the sample surface increase. Two models for thermal emission of rock surface were examined using the measured emissivity spectra. The first is the linear abundance mixing model and the second treats the DV coating as a layer which absorbs and transmits the electromagnetic wave in the TIR region. We found that the second model can explain the measured spectra better.
Thickness of DV coating was investigated using airborne TIR remote sensing data acquired over Cuprite area, Nevada in 1990. The proposed thickness index based on the model described above, was calculated using emissivity spectra derived from the remote sensing data. The spatial distribution of the DV thickness index in Cuprite area derived from the airborne data showed good agreement with the relative extent of DV coating.