Investigation of serious tornado damage in Saroma-cho, Hokkaido

从气象和工程的角度对2006年11月7日发生在北海道沙罗町的龙卷风及其造成的损失进行了调查。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，即一对强烈的上下气流区和穹窿和胚幕。焚风现象是由南风吹过山脉造成的。这一现象极大地影响了龙卷风的产生。场地周围复杂的几何特征是龙卷风形成的另一个因素。采用多普勒雷达资料和数值云分辨风暴模拟器相结合的方法对龙卷风进行了短时预报。利用双多普勒雷达分析得到的水平风速和雨的混合比改进了估计。对建筑物损坏情况的详细调查显示，受损区域长约1公里，宽约100至250米。大部分碎片散落在伊瓦萨北部地区，一些碎片飞了20多公里，落入了鄂霍次克海。向受灾地区的151个家庭分发了一份问卷调查。从问卷调查的初步结果出发，研究了坝龄与房屋结构、龙卷风下的气象现象、人们的行为和政府行为之间的关系。由于碎片的冲击，房屋受到了相当大的破坏，一些屋顶被吹走。研究了飞屑损坏外包层材料的检验标准、规范和方法。研究结果对进一步评价龙卷风的对策具有一定的参考价值。

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.