Research on the evolution of rain cells at the Nagasaki Peninsula and the disaster due to the heavy rainfalls at the Shimabara Peninsula

位于长崎县长崎半岛的千济河谷是一个向南开放的很深的山谷，可以推测是对流降雨产生的地形效应的作用。在长崎半岛附近演化的暴雨经常向岛原半岛移动，有时还会在云顶-船根达克火山周围形成蓬松的泥石流。本研究的主要目的是观察长崎半岛雨云的演变和发展过程。研究结果如下：(1)1995年7月2日和7月11日，长崎大学的RHI雷达观测到了从东-长崎地区延伸到以沙湾地区的线状雨回波，持续时间长达10小时以上。这些极具特征和显著的降雨回波出现在同样的大气条件下，即来自海洋的温暖潮湿的南风在长崎地区占优势。这个Conditi…更强烈地表明，深谷增强了垂直运动。(2)线状、持续时间长的回波与上述情况基本相同。在1996和1997年的季风季频繁出现。所有产生这些回波的大气条件都可以描述为地面的南风。除了这一显著的雷达回波外，还观察到强度相对较弱的第二和第三线状回波，其方向与主要回波平行。由于这些微弱的线性回波也对应于向南开放的小山谷，这些第二和第三回波的出现有力地支持了长崎半岛山谷效应的假说。3)随着火山活动的沉默和大坝的修建，云仙山周围的灾难性泥石流减少。尽管如此，仍然需要仔细观察暴雨，因为火山泥石流经常发生在河床上。较少

The Chiji Valley at the Nagasaki Peninsula in Nagasaki Prefecture is a very deep valley which is open to the south direction, and can be inferred as a role of topographical effect of convective rainfall generation. The rain storms evoluted near the Nagasaki Peninsula often move towards to the Shimabara Peninsula and sometimes occure the velcanic debris flows around the Unzen-Fugendake Volcano.The main purpose of this study is to observe the evolution and development process of the rain cells at the Nagasaki Peninsula. The results obtained in this study are as follows ;(1) The line-shaped rain echoes, which extended from the Higashi-Nagasaki area to the Isahaya Bay region and lasted as long as ten hours or more, were observed by the RHI radar of Nagasaki University at July 2 and July 11 both in 1995. These very characteristic and significant rain echoes appeared under the same atmospheric condition that the warm and humid south wind from the sea prevails over Nagasaki area. This conditi … More on strongly suggests the enhancement of the vertical motion by a deep valley.(2) The line-shaped and long-lasting echoes almost same as the above cases. were observed frequently in the monsoon seasons in l996 and 1997. All the atmospheric conditions ge*nerated these echoes can be characterized as the south wind at surface. In addition to this significant radar echoes, the scond and third line-shaped echoes with relatively weak intensity were observed in a parallel direction with the main echoes. Since these weak linear echoes are also corresponding to small valleys open to the south, the appearance of these second and third echoes strongly supports the hypothesis of the valley effects at the Nagasaki Peninsula.3) The disastrous debris flows aroud Mt.Unzen were decreased according to the silence of the volcanic activity and the contruction of dams. In spite of this, the careful watch for heavy rainfalls can be still needed, because the vlcanic debris flows have taken place frequently in the riverbed. Less