台風0418号通過時の厳島神社周辺における地形性の強風を再現する試み

Abstract

台風0418号が通過した際に，厳島神社周辺では地形性の強風が発生し各種被害が起きた。また，過去にも同じようなコースを台風が進むときに，同様な被害を受けたことが報告されている。本報では，このような地形性の強風の実態を解明するために，数値シミュレーションにより台風通過時の厳島神社周辺における強風場を再現した。その際，メソスケールの気象場を解析できるPSU/NCAR MM5，および，LESを用いた狭域スケールの非定常・非線形風況シミュレータRIAM-COMPACTを用いた。計算結果は実測値や被害の調査結果と比較し，精度や境界条件の与え方等，計算を行う際の問題点について検討を行った。また，計算結果から求めた最大風速分布は，建物や人的被害の分布と良く対応しており，強風被害予測の可能性を示した。

The strong wind fields around Miyajima in Hiroshima Bay were simulated numerically during Typhoon Songda in 2004. The PSU/MM5 model was used for the calculation of meso-scale regions. The strong wind that passed over the sea and blew into the Hiroshima Bay was simulated. The predicted wind fields were examined comparing with the observed records and the field investigation of damage to the human and buildings. The calculated maximum wind speed map was well correlated to the distribution of damage rate by strong wind in Hiroshima Prefecture. Unsteady wind fields were also computed by Large Eddy Simulation in the fine region around Miyajima. The local wind characteristics caused by the topography around Itsukushima Shrine were investigated. The down flow along the valley to the south of the shrine was simulated in the neutral atmospheric condition. The local wind flows around the shrine were discussed.