Structure and Dynamics of Convective Clouds that Cause Wind Hazards

通过数值模拟和分析来自多普勒雷达的观测资料，研究了在日本等相对潮湿地区产生龙卷风和下击暴流的对流云的结构和动力学。为了阐明产生龙卷风对流云的环境特征，编制了日本1961年至2000年的龙卷风数据库，并利用日本气象厅1999.1~1988年的高空探测资料，对表征中尺度环境的所谓总体参数进行了检验。造成龙卷风的风暴1990年9月19日晚，关东区至少发生了三次龙卷风，与9019号台风有关。我们的多谱勒观测显示，9个微型超级单体出现在该区上空，并阐明了它们的详细结构。用2100JST的塔特诺高空探测作为水平均匀环境的数值模拟再现了观测到的…迷你超级细胞的更多特征出人意料地好。模拟的风暴每小时显示一次世代变化。中气旋的垂直涡度主要是由于环境风中水平涡度的倾斜而产生的。对1996年7月5日在千叶县产生两次龙卷风的微型超级单体的另一次多普勒雷达观测清楚地发现了它的世代变化。用观测资料分析了1994年9月8日在崎玉县水户镇发生的一次造成破坏性下击暴流的风暴。利用JST 1500时前桥和Tateno的高空探测作为水平均匀环境进行了数值模拟，较好地再现了风暴的观测特征。研究发现，下击暴流是由高层的冰雹和小球的加载引发的，其次是OC层附近小球和冰雹的融化，其次是雨滴的蒸发。较少

The structure and dynamics of convective clouds that produce tornadoes and downbursts in relatively humid regions like Japan was studied by means of a numerical simulation and by analyzing observational data derived from Doppler radars. In order to clarify the characteristics of the environment for tornado-producing convective clouds, a tornado database between 1961 and 2000 in Japan was compiled, and so-called bulk parameters that characterize meso-scale environment was examined based on the upper air sounding data of Japan Meteorological Agency between 1988 and 1999.1. Tornado-producing stormsOn the evening of 19 September 1990, at least three tornadoes occurred in Kanto District in association with Typhoon 9019. Our Doppler observation revealed that nine mini-supercells occurred over the District and their detailed structure was clarified. A numerical simulation in which the upper air sounding at Tateno at 2100JST was used as a horizontally uniform environment reproduced the observe … More d characteristics of the mini-supercell surprisingly well. The simulated storm exhibited a generation change every an hour. The vertical vorticity of the mesocyclone was found to be produced principally by tilting the horizontal vorticity in the environmental wind. Another Doppler radar observation of a mini-supercell that spawned two tornadoes in Chiba prefecture on 5 July 1996 detected clearly its generation change.2. Downburst-producing stormsA storm that caused damage-producing downbursts in Misato town in Saitama prefecture on 8 September 1994 was analyzed by using observational data. A numerical simulation in which the upper air soundings at Maebashi and Tateno at 1500JST was used as a horizontally homogeneous environment reproduced the observed characteristics of the storm well. The downburst was found to be initiated by the loading of graupel and hail at the upper level, and then intensified principally by the melting of graupel and hail near the OC level and secondly by evaporation of rain drops. Less