Investigation of serious tornado damage in Saroma-cho, Hokkaido

对2006年11月7日发生在北海道萨罗马町的龙卷风及其造成的破坏，从气象学和工程学的角度进行了调查。澄清了以下几点。带来龙卷风的积雨云高约10公里，直径约20至30公里。它具有典型的超级单体特征，即，一对强上下通风区和拱顶及胎帘。焚风现象是由南风从山上吹过引起的。这种现象极大地影响了龙卷风的生成。该地点周围复杂的几何特征是龙卷风生成的另一个因素。利用多普勒雷达资料和数值云分辨风暴模拟器，对一次龙卷风进行了短期预报。利用双多普勒雷达分析得到的水平风速和雨水混合比，改进了估计。对建筑物受损情况的详细调查表明，受损区域长约1 km，宽约100至250 m。大多数碎片散落在岩佐县北方地区，有些碎片飞到20多公里外，到达鄂霍次克海。向整个受灾地区的151个家庭分发了一份问卷调查。从调查问卷的初步结果出发，研究了房屋结构、龙卷风下的气象现象、人们的行为和政府行为与坝龄的关系。由于飞行碎片的撞击，房屋受到相当大的破坏，一些屋顶被吹走。综述了飞行碎片对建筑外墙外覆层材料损伤的标准规范和检测方法。研究结果对进一步评估龙卷风防御措施有一定的参考价值。

An investigation was carried out of a tornado and damage caused on November 7, 2006 in Hokkaido, Saroma-cho from both meteorological and a engineering viewpoints. The following points were clarified. The cumulonimbus that brought the tornado was about 10 km high and 20 to 30 km in diameter. It had typical supercell characteristics, i.e., a pair of a strong up and down draft regions and the vault and embryo curtain. The foehn phenomenon had been caused by wind from the south flowing over mountains. This phenomenon greatly affected the generation of the tornado. A complex geometrical feature around the site was another factor in the tornado's generation. A technique using Doppler radar data and numerical cloud resolving storm simulator was applied to a short-period tornado forecast. Applying horizontal wind speeds and the mixing ratio of rain obtained by dual Doppler radar analysis improved the estimation.A detailed investigation of damage to buildings showed that the damaged area was about 1 km long and about 100 to 250 m wide. Most of the debris was scattered in the northern area of Iwasa district, while some flew more than 20 km, reaching the Okhotsk-sea. A questionnaire survey was circulated to 151 families throughout the damaged area. From the primary result of the questionnaire, relations between dam age and structure of houses, meteorological phenomena under the tornado, people's behaviors and government actions were studied. There was considerable damage to houses due to the impact of flying debris, and some roofs were blown off. The standard spec and method for inspecting the exterior cladding materials damaged by flying debris were surveyed. The results should be valuable for further evaluation of countermeasures to tornados.