Generation Mechanism of Flow Pattern Change and Rapid Water Exchange in Mutsu Bay

封闭海湾中的水流结构和水质受潮汐和风况的影响。此外，在通向海峡的海湾中，海峡水流结构的微小变化对海湾的水交换影响很大，为了弄清这种湾的水交换机制，我们在位于日本北部的木津湾入海口附近进行了实地观测。木津湾正在向连接日本海和太平洋的津格鲁海峡开放。利用ADCP和STD对流动结构和密度结构进行了测量。夏季存在波幅较大的内波，湾口附近以诱导流为主。2.根据海峡两端的潮流特征，可以确定湾口的流态。3.东风时湾口北向流的产生是由设置水的外流引起的。4.剩余环流形成于塔皮角后方，影响湾口的流动结构。5.根据低压街道，水位上升和风的产生激活了水的交换。

Flow structures and water qualities in an enclosed bay are influenced by conditions of tide and wind. Moreover, in a bay opening to a strait, a little change in flow structure of the strait greatly affects water exchange in the bay.To clarify the mechanism of the water exchange in such a bay, we have carried out field observations around the mouth of Mutsu Bay, located in the North Japan. The Mutsu Bay is opening to the Tsugaru Strait connecting the Japan Sea with the Pacific Ocean. Flow structure and density structures were measured by using an ADCP and a STD.Main results in this study are summarized as follows.1. There exists internal wave with large amplitude in summer, and the induced flow is dominant in the vicinity of the bay mouth. 2. The flow pattern in the bay mouth could be identified by tidal characteristics at the ends of the strait. 3. The generation of the northward current in the bay mouth at east wind is caused by outflow of the set-up water. 4. The residual circulation is formed behind the Tappi Cape, and affects the flow structure in the bay mouth. 5. The water exchange is activated by rise of water level and generation of wind according to the street of the low-pressure.