陸上地形および表面粗度を考慮した高潮の数値計算

Abstract

Wind fields model of typhoon is an aspect that has been made in making more precise surge models by incorporating various physical phenomena. Storm surge simulation in small closed basins surrounded by mountains such as Osaka Bay is difficult especially in the wind field prediction or simulation, which is affected by complex land topography. Fujita's typhoon model simple typhoon models which are derived from the same concept, that is superposition of pressure gradient and moving winds. Attenuation parameters for the gradient and moving wind fields in such a simple typhoon model are usually determined by observations.Yoshizumi (1968) proposed a typhoon wind field model which describes the lower-layer winds in a moving typhoon with consideration of surface friction. It is employed here to estimate the typhoon wind field taking into account the effect of friction.In areas surrounded by mountains, the wind field is affected by both small-scale roughness such as trees and houses and by the large-scale land topography itself. As the wind field described by Yoshizumi's model does not include the effect of land topography, we introduce the 'MASCON' (mass conservation) model to take into account the effects of deceleration and acceleration of wind velocity due to land topography. This is a new model of typhoon wind field which is developed here by combining the Yoshizumi's and MASCON models. The pressure field is formulated by Schloeiner's equation which assumes a symmetric pressure pattern.Hindcast of typical storm surges in Osaka bay and Ise bay have been done by using the proposed new model to test its applicability in these bays. It has been made clear that the new typhoon model can predict a wind field as well as storm surge without any empirical attenuation parameters of typhoon model.