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Study on Water Exchange between Osaka Bay and Pacific Ocean

大阪湾与太平洋水交换研究

基本信息

批准号：
09650565
负责人：
NAKATSUJI Keiji
金额：
$ 2.05万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1998
项目状态：
已结题

项目摘要

According to the field survey conducted in Ki-i Channel in summer of 1995, its results indicated that lots of nutrients such as nitrogen (N) and phosphorus (P) of Pacific Ocean intrudes into Osaka Bay.Their volume surprisingly corresponds to total value discharged from coastal land area.One of objects of the present study is to verify the result of field survey.Other purpose is to clarify the inflow fluxes of N and P into Osaka Bay by field survey and to examine the flow structure in detail by a three-dimensional baroclinic flow model.(1) Field survey to clarify fluxes of N and PSimultaneous measurements in Osaka Bay were conducted on 23rd August in 1997.12 hours measurements of velocity, temperature and salinity, and water sampling were done in the sections across Osaka Bay along about 20 m depth and Tomogashima Channel.And, during the same time, STD and water sampling were done in Akashi Straits.As a result, in regard to the balance of N, 24 ton during one day inflows through Akashi Straits and 35 ton outflows thorough Tomogashima Channel.In the case of P.68 ton inflows and 1 ton outflows That means that 11 ton of N outflows from Osaka Bay and 67 ton of P inflows.On the other hand, 16 ton of N and 5 ton of P are transported toward the head of bay by estuarine circulation.(2) Numerical experimentAt first, the flow and density structures are computed in the large scale domain including Osaka Bay, Harimanada Sea and Ki-i Channel with 1,000 m horizontal resolution and 10 layers in vertical direction in order to obtain the boundary conditions for the small scale domain of computation near the Kitan Straits.Secondly, the small scale computation with 250 m clarifies the production mechanism of large scale eddy near the straits, residual current system, water exchange and so on.

1995年夏季在岐一海峡进行的野外调查结果表明，太平洋的氮、磷等大量营养物质侵入大阪湾。令人惊讶的是，它们的体积与沿海陆地排放的总量相对应。本研究的目的之一是验证野外调查的结果。另一个目的是通过实地调查来阐明流入大阪湾的氮和磷的通量，并通过三维斜压流动模型来详细研究流动结构。1997年8月23日在大阪湾同时进行了12小时的速度、温度和盐度测量，并在大阪湾约20 m深度和富岛海峡进行了水样采集。同时，在明石海峡进行了性病和水样采集。因此，就氮的平衡而言，一天内24吨通过明石海峡流入，35吨通过富岛海峡流出。以p68吨流入和1吨流出为例，这意味着大阪湾流出了11吨氮，流入了67吨磷。另一方面，16吨N和5吨P通过河口环流向湾头输送。(2)数值实验首先在水平分辨率为1000 m，垂直方向为10层的大阪湾、哈里马纳达海和吉一海峡等大尺度区域进行了流场和密度结构计算，得到了Kitan海峡附近小尺度计算区域的边界条件。其次，通过250 m的小尺度计算，阐明了海峡附近大尺度涡、残流系统、水交换等的产生机理。