Studies on Annual and Interannual Variations of Oceanic Thermal Domes

海洋热穹年及年际变化研究

基本信息

批准号：
03402015
负责人：
YAMAGATA Toshio
金额：
$ 12.1万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (A)
财政年份：
1991
资助国家：
日本
起止时间：
1991 至 1992
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-03402015/
关键词：
Oceanic thermal dome Observation Ocean general circulation model Seasonal variation Interannual variation The Costa Rica Dome The Guinea Dome The Angola Dome 熱フラックススル-・フロ-ドリフタ-・ブイコスタ・リカ・ド-ム

项目摘要

We studied both annual and interannual variations of oceanic thermal domes in the Pacific and the Atlantic. In particular, the Costa Rica Dome, the Mindanao Dome, the Angola Dome and the Guinea (Dakar) Dome are analysed in detail using several high-resolution ocean general circulation models. The Costa Rica Dome was also investigated utilizing the cruise of R/V Kaiyo-maru in January 1992. During the cruise both hydrographic (ADCP,XBT,CTD, water sampling) and meteorological observations were conducted. The following is the main outcome of the present research program. 1) We analyzed the model sensitivity to the surface heat and momentum fluxes and the effects of small islands using the Indo-Pacific model. It is found that the transport of low-latitude western boundary currents is much affected by those flux conditions. Also,even a small island can affect seriously surrounding oceanic conditions if it is located in strong currents. 2) An Indo-Pacific ocean model demonstrates that the sea … More sonal Costa Rica Dome cannot be generated well in some years like 1981 and 1983 because of lack of elements of formation due to basin-scale ocean-atmosphere variabilities. The model also shows an ability to capture several interesting synoptic events. For example, the Geosat altimetry data shows that an unusually strong anticyclone was generated in the Gulf of Tehuantepec in October, 1987 and then moved westward keeping its identity. The eddy was traced for a certain period by the EPOCS drifter 6858. This interesting event is clearly resolved in the model forced by the ECMWF winds but the simulated eddy strength (estimated by rotation speed and dynamic height anomaly) is one half of the observed one. This is mostly due the winds that are too weak, particularly in terms of the curl of the stress. 3) A general ocean circulation model for the Atlantic Ocean is used to analyze the seasonal variations in the Guinea Dome and Angola Dome regions. Model results are the following. The model Guinea Dome is cooled from June trough October due to active divergence of the heat transport, although the cooling rate is partly counteracted by the surface heating. The cooling is mostly related to the intensified positive curl of the local wind which converges into the ITCZ migrating northward during the boreal summer and fall. The coastal Guinea region experiences heating twice a year due to propagation of coastal downwelling Kelvin waves. The model Angola Dome is cooled from March through September. The horizontal divergence of the heat transport associated with the cold subsurface SECC(or SEUC) always tends to cool the Angola Dome. During the austral summer,however,the surface warming cancels the above current- induced cooling. The coastal Angola region is also much affected by the poleward propagation of the coastal downwelling Kelvin waves from the tropics twice a year. The generation of the downwelling Kelvin waves is due to the semiannual intensification of the westerly compone Less

我们研究了太平洋和大西洋海洋热穹顶的年度和年际变化，特别是使用几个高分辨率海洋对哥斯达黎加穹顶、棉兰老岛穹顶、安哥拉穹顶和几内亚（达喀尔）穹顶进行了详细分析。 1992 年 1 月，还利用 R/V Kaiyo-maru 的巡航对哥斯达黎加圆顶进行了调查。进行了（ADCP、XBT、CTD、水采样）和气象观测，以下是本研究计划的主要成果： 1）我们利用模型分析了地表热和动量通量的敏感性以及小岛屿的影响。印度-太平洋模型发现，低纬度西部边界流的输送受这些通量条件的影响很大，而且，即使是一个小岛屿，如果位于强流中也会严重影响周围的海洋条件。印度-太平洋模型表明，由于盆地尺度的海洋-大气变化而缺乏形成要素，因此在 1981 年和 1983 年等年份无法很好地生成海洋哥斯达黎加圆顶。例如，地球卫星测高数据显示 1987 年 10 月在特万特佩克湾产生了异常强烈的反气旋，然后发生了移动。 EPOCS 漂流器 6858 在一段时间内追踪了涡流。这个有趣的事件在 ECMWF 风强制的模型中得到了清晰的解决，但模拟的涡流强度（通过旋转速度和动态高度异常估计）是其中之一。这主要是由于风太弱，特别是在应力旋度方面。 3) 使用大西洋的一般海洋环流模型来分析季节变化。几内亚穹顶和安哥拉穹顶地区的模型结果如下所示，由于热传输的活跃发散，模型几内亚穹顶从 6 月到 10 月有所冷却，尽管冷却速率大部分被表面加热所抵消。与北半球夏季和秋季期间汇聚到向北迁移的 ITCZ 的当地风的增强正旋度有关，由于沿海传播，几内亚沿海地区每年经历两次加热。下涌开尔文波从三月到九月冷却与寒冷的地下 SECC（或 SEUC）相关的热量传输的水平散度总是倾向于使安哥拉穹顶变冷。消除了上述电流引起的冷却。安哥拉沿海地区还受到每年两次来自热带的沿海下降流开尔文波向极地传播的影响。波浪是由于西风分量半年加强所致更少