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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的年和年际变化。特别是，哥斯达黎加穹、棉兰老岛穹、安哥拉穹和几内亚（达喀尔）穹使用几个高分辨率海洋环流模式进行了详细分析。1992年1月还利用“Kaiyo-maru”号考察船对哥斯达黎加Dome进行了调查。在航行期间，进行了水文观测（ADCP、XBT、CTD、水取样）和气象观测。以下是本研究计划的主要成果。1)利用印度洋-太平洋模式分析了模式对地表热量和动量通量的敏感性以及小岛屿的影响。结果表明，这些通量条件对低纬西边界流的输运有很大的影响。此外，即使是一个小岛，如果位于强海流中，也会严重影响周围的海洋条件。2)印度-太平洋海洋模型表明， ...更多信息由于海盆尺度的海气变化，缺少形成要素，在某些年份（如1981年和1983年）不能很好地形成sonal哥斯达黎加穹。该模型还显示了捕捉几个有趣的天气事件的能力。例如，地球观测卫星测高数据显示，1987年10月特万特佩克湾产生了一个异常强烈的反气旋，然后向西移动，保持其特征。EPOCS漂移器6858在一定时间内跟踪了该涡流。这个有趣的事件是清楚地解决了在模式强迫ECMWF风，但模拟的涡动强度（估计的旋转速度和动态高度异常）是观测的一半。这主要是由于风太弱，特别是在应力旋度方面。3)本文用一个大西洋环流模式分析了几内亚穹和安哥拉穹的季节变化。模型结果如下。由于热输运的积极发散，模型几内亚穹从6月至10月冷却，尽管冷却速率被地面加热部分抵消。这种冷却主要与北方夏季和秋季当地风的正旋度增强有关，这些正旋度汇聚到ITCZ向北迁移。几内亚沿海地区每年经历两次加热，这是由于沿海下沉开尔文波的传播。模型安哥拉圆顶从三月到九月冷却。与冷的次表层SECC（或SEUC）相关的热传输的水平发散总是倾向于冷却安哥拉穹。而在南半球夏季，地表暖化抵消了上述海流引起的冷却作用.安哥拉沿海地区也受到每年两次来自热带的沿海下沉开尔文波向极地传播的影响。下沉Kelvin波的产生是由于西风分量的半年增强