Meteorological data during typhoons, measured at 46 JMA meteorological observatories in Japan from 1975 to 1997, are analyzed from the viewpoint of building damage. The number of typhoons used for the present analysis ranges from 29 at Sapporo to 110 at Okinawa. Special attention is paid to the gust factor and the intensity and amount of precipitation at and after the occurrence of the maximum peak gust. Based on the results, a simple model of the gust factor is provided, in which the effect of terrain roughness is considered. Furthermore a stochastic model is proposed for the amount of precipitation as a function of the shortest distance between the typhoon center and the observation site. These models can be incorporated into a prediction model of typhoon-induced building damage, which the authors are now developing.
In order to develop an overall efficient and accurate model of simulating an unsteady three-dimensional airflow over complex terrain with characteristic length scales on the order of kilometers, we have been examining the large-eddy simulation (LES) technique using a finite-difference method (FDM). These LES codes are referred to as the RIAM-COMPACT (Research Institute for Applied Mechanics, Kyushu University, Computational Prediction of Airflow over Complex Terrain), and are based on two grid systems and corresponding variable arrangement: one is an orthogonal staggered grid; the other is a generalized curvilinear collocated grid. In this paper, using the RIAM-COMPACT based on a generalized curvilinear collocated grid, we have performed the calculations of a non-stratified airflow over real complex terrain. This area covers the new campus of Kyushu University. To investigate more clearly the influence of topography on the airflow over the new campus area, we employed nested grids: the outer grid domain is 9.75km × 4.65km × 1.46km with horizontal grid spacing of 50m and the inner grid domain is 5km × 2.7km × 1.46km with horizontal grid spacing of 25m. The numerical results were compared with the wind tunnel experiment, and airflow characteristics due to the topographic effect, such as the wind speed-up and the separated flow, were successively simulated.