A consideration of the availableness of MODIS data to assess a volcanic ash fall

It is important to grasp the situation of the ash fall at short interval for a volcanic disaster-prevention. Clouds and volcanic smokes reduce the opportunities to observe a volcano by a satellite's optical sensor. Therefore it is preferable to use data of a sensor that is able to observe same area with high frequency. MODIS sees every point on the earth every 1-2 days and provides NDVI data with 250m spatial resolutions. The purpose of this study is to consider the availableness of MODIS data to assess the situation of the volcanic ash fall. The test site is Miyake-jima, one of the active volcanic island in Japan. It is verified that a rate of change of NDVI between before and after erruptions correlates with the amounts of ash fall.