Atmospheric Dispersion of Volcanic Gas and Clouds

利用卫星遥感资料、地面摄像机观测资料、气象资料和大气中二氧化硫浓度资料，研究了樱岛火山云及其伴生气的喷射和扩散。澄清了以下几点：(1)火山口上方1000 ~ 4500 m高度的喷发土块的上升和漂移特性，以及卫星观测数据。(2)在海拔1 ~ 2 km的高空风速下，连续喷射羽流垂直形态的差异。(3)从卫星和地面观测到的火山灰云垂直厚度内的各种水平分散模式主要由风切变决定，并通过垂直切变模式成功地模拟。(4)在风速大于10 m/s的情况下，羽流沿着山背风波流动，造成火山脚下空气中二氧化硫浓度达到ppm的高浓度事件。(5) NOAA卫星观测到的下游130 ~ 150 km高原火山气体与火山灰云的远距离输送。将卫星探测火山云的研究扩展到日本九州及周边的其他火山，即琉球群岛的麻生、云仙等火山。部分结果可以在以下主页中看到：http: //www-rk.edu.kagoshima-u.ac.jp/sci/volc/index_e.htmlhttp: //www-rk.edu.kagoshima-u.ac.jp/sing/index_e.htm

Ejection and dispersion of volcanic clouds and accompanied gas from Mt.Sakurajima were studied based on remote sensing data from satellites, ground observation by video cameras, meteorological data, and sulfur dioxide concentration data in the air.Following points are clarified :(1)Properties of rise and drift of eruption clods up to the height 1000-4500 m above the crater, and their observation by satellite data.(2)Difference of the vertical shapes of continuously emitted plumes according to the velocity of upper winds at the altitudes 1-2 km above the sea level.(3)Various patterns of horizontal dispersions essentially determined by the wind shear within the vertical thickness of the ash cloud as observed from satellites and the ground, and simulated successfully by a vertical shear model.(4)Flow of plumes along the mountain lee waves under winds stronger than 10 m/s, resulting high concentration events of sulfur dioxide at the foot of the volcano with the level of ppm in the air.(5)Long range transport of volcanic gas detected at highlands 130-150 km downstream together with ash clouds as observed by NOAA satellites.The research of satellite detection of volcanic clouds was extended to other volcanoes in Kyushu and the surrondings in Japan, i.e., Aso, Unzen and others in Ryukyu Islands.Parts of the results may be seen in the following home pages :http : //www-rk.edu.kagoshima-u.ac.jp/sci/volc/index_e.htmlhttp : //www-rk.edu.kagoshima-u.ac.jp/sing/index_e.htm