Attempt on Surveillance of Volcanic Activity by Eruption-Cloud Image from Artificial Satellite

Abstract

Recently, images of eruption clouds have been well and frequently returned by artificial satellites such as NOAA, LANDSAT and GOES. Orbit satellites have a high resolution of images, but time intervals to get images are rather long for detection of on-going eruptive activities. Resolution of geosynchronous satellites is insufficient to detect small eruption clouds, but the images are routinely returned 14 times a day in case of GMS (Geostationary Meteorological Satellite), and this interval is effective to detect eruption clouds by rather big volcanic eruptions. In this paper, GMS images of eruption clouds by rather big eruptions of Alaid, Asama-Yama, Pagan, Soputan and Galunggung which took place in 1981-1982 are summarized. Detection of eruption clouds by satellite image is severely hampered by existence of atmospheric clouds around volcanoes, but ca. 10 km across and 6-7 km high eruption clouds are distinguished by GMS images under a good condition. Horizontal eddy diffusivity and thermal energy release by eruption cloud are estimated by the methods of GIFFORD (1959) and BRIGGS (1969), respectively. Then, the author tried to distinguish individual eruptions during the whole eruptive activities by inspections of changes of forms and density of eruption clouds in GMS images, and estimated the total thermal energy release of the whole eruptive activities of five volcanoes. Although these results should be correlated based on precise ground observation data of respective eruptions, it is suggested that there are possibilities to know the intensity of eruptions and to watch the variation of eruptive activities by analysis of eruption clouds from GMS images.