1994 年 14 巻 3 号 p. 230-241
A method for the separation of kinetic temperature and spectral emissivity on the thermal infrared multispectral remote sensing data of the land surface was proposed. This method, named Mean-Maximum Difference (MMD) method, is based on an empirical relationship between the mean and the variation of spectral emissivity of the natural materials in the thermal infrared region. To give an additional equation to the under-determined problem of the thermal infrared remote sensing, the relationship between the mean (M) emissivity and the maximum difference (MD) which is the difference between maximum and minimum values of a spectrum was assumed to be linear. The evaluation using laboratory emissivity spectra of various natural materials indicated the assumption of the linear relationship between M and MD is reasonable.
The effects of vegetation in a rock-dominated field and the reflection of the environmental radiation were studied using simple numerical simulations. The results suggested that although the in-situ pixel-averaged spectra may differ from laboratory spectra of rock samples, their Ms and MDs satisfy the same linear relationship as the laboratory spectra.
The MMD method was applied to airborne thermal infrared multispectral remote sensing data, and emis-sivity spectra were obtained from the rhyolite-dominated surface, the coniferous forest, and their mixture. These spectra showed distinct features such as the emissivity trough due to Si-O bond stretching in rhyolite spectra, relatively high and flat spectra for the forest, and the gradual spactral change over the transect from the forest zone to the rhyolite zone. These were consistent with published laboratory spectra of the same kind of materials though some discrepancies probably due to residual errors of the atmospheric correction, vegetation, and the reflection of the environmental radiation were found.