Abstract
The purpose of this study is to evaluate the influence of the atmospheric correction errors on ASTER TIR data, especially in humid atmosphere such as in Japanese summer.
To understand the characteristics of humid atmosphere, we originally derived typical new model atmospheres of Japan from Aerological Data of Japan. These models are the average seasonal profiles of temperature and relative humidity in North, Middle and South areas of Japan. Then these were compared with the generic model atmospheres in LOWTRAN 7 for transmittance. These results indicate that the transmittance of Japan Middle area Summer model and Japan South area Summer model is smaller than that of Tropical model in LOWTRAN 7, which reflects the difference of total water vapor content for each atmospheric model.
The influence of the error of water vapor content (WVC) on the surface brightness temperature (SBT) was evaluated by the computer simulations using LOWTRAN 7 from a viewpoint of atmospheric correction. The results are summarized as follows : The SBT errors are more sensitive to the WVC errors in humid model atmospheres. Thing to be emphasized is that the SBT errors in Japanese summer atmosphere are relatively large. These results indicate that the summer data observed in east or southeast Asia would need careful atmospheric correction. The general tendency was also found that the SBT error of Band 10 and 14 are larger than those of the other ASTER TIR bands.
Moreover, the sensitivity of the SBT errors to each WVC error was evaluated in several atmospheric layers, which were equally divided multi-layers in troposphere. It is shown as a general trend that the sensitivity of the verical profiles on SBT decreases as the altitude of atmosphere increases. In detail, however, it is also indicated that the SBT errors of Band 10 are highly influenced by the WVC errors in the middle and upper layers, and that the sensitivity of each layer varies with real surface temperature.
