数値実験による東京湾の海水交換に関する検討

抄録

Exchange of sea water through the mouth of an enclosed bay is essential for water quality and substance circulation in coastal zone. For the purpose of estimating the current state of water exchange, box models have been mainly used. However, in order to investigate the mechanism of water exchange or to predict the future state, numerical simulations are necessary which can consider physical processes occurred in the interested area. In this paper, a multilevel model is employed for the evaluation of water exchange in Tokyo Bay. At first, water exchange due to the estuarine circulation in winter and summer was calculated and the results of numerical simulations showed same tendency as the estimation by the box model. Using the same model, the relationship between the river discharge and the estuarine circulation were investigated. Next, the numerical model was applied to the estimation of water exchange when some typhoons with strong wind and large amount of rainfall pass near Tokyo Bay. It was found that the water exchange ratio during such eventual phenomena as typhoon attacks can be several times as large as that in the normal condition.