MODISデータを用いた合成画像作成手法の開発

抄録

This paper focuses on the evaluation of compositing algorithms of MODerate resolution Imaging Spectroradiometer (MODIS) . The atmospheric effects of channel 1-7 have been investigated by radiative transfer simulation using 6S code over variety of aerosol and climatic conditions. As a result, blue wavelength (channel 3) was found to be the most subject to atmospheric effects and its apparent reflectance values were higher than other channels. However, this method is subject to select cloud shadows as a optimum values. To avoid this problem, the combination of minimum blue constrained with thermal channel criteria is newly developed based on the assumption that the cloud shadow is cooler than normal pixels. These two approaches, to say, the minimum blue criterion (MinB) and the minimum blue and maximum thermal criteria (TMinB) have been tested along with five approaches including the maximum NDVI criterion (MaxN), the maximum temperature criterion (MaxT), the NDVI criteria followed by minimum scan angle (NMinS), the thermal criteria followed by minimum scan angle (TMinS) and the NDVI and thermal criteria followed by minimum scan angle method (NTMinS), to improve on the heritage of Advanced Very High Resolution Radiometer (AVHRR) . Then the 10 day composite images over Japan main islands have been generated using the above mentioned seven approaches. The comparative performances of these seven methods are judged from five criterion including cloud screening, satellite zenith angle, smoothness of the image, snow/ice identification and cloud shadow. It is concluded that the TMinB method produces fairly consistent results with possible refinements and more sophisticated methods to escape from cloud shadows.