| 2002年夏季广东陆架边缘上升流海域的内潮现象及其局地反馈初探 |
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| 引用本文： | 潘爱军,李立,郭小钢,许金电.2002年夏季广东陆架边缘上升流海域的内潮现象及其局地反馈初探[J].台湾海峡,2012,31(2):151-159. |
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| 作者姓名： | 潘爱军 李立 郭小钢 许金电 |
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| 作者单位： | 国家海洋局第三海洋研究所,福建厦门,361005 |
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| 基金项目： | 国家海洋局第三海洋研究所基本科研业务费专项资金资助项目，国家自然科学基金资助项目，国家重点基础科学研究专项经费资助项目 |
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| 摘 要： | 基于2002年夏季开展的"中国近海环流形成变异机理、数值预测方法及对环境的影响"观测项目获得的往复走航温盐流资料,结合同期的卫星观测(风、SST、海表动力高度)数据,初步探讨了粤东陆架边缘上升流区的内潮现象及其局地反馈特征.研究结果表明:粤东陆架边缘海域存在显著的、间歇性的相对低温海水的沿陆坡涌升现象,其中A航段的低温(18～23℃)海水涌升发生在约50～150m深度,B航段的低温(<18℃)海水涌升则主要位于150 m以深.由于观测期间海表风变化很小,而海洋涡旋在几周至几个月内相对稳定,并且研究海域涡旋对流场的影响似乎局限于75 m以浅的上层海洋,因而A、B航段的差异显然不能用海表风或海表动力高度变化来解释.进一步的分析表明粤东陆架边缘上升流区存在显著的内潮现象,尽管资料所限使得我们无法准确判定该内潮性质,往复走航海流剖面的确揭示了1阶和5阶内潮模的存在.内潮的不同模态极大地改变了上层海洋的热力和环流结构;低阶内潮模导致沿最大温度水平梯度处水温的剧烈垂向起伏(>30 m)以及跃层两侧的海流反向现象;高阶内潮模导致垂直陆坡方向水平流速的多次反向,强烈的流剪切可能与增强的混合联系在一起.导致低阶内潮模(A航段)向高阶内潮模(B航段)转变的原因可能是由于内潮特征线倾角与地形坡度比较接近而激发的"临界反射"效应.分析结果还表明,不同内潮模态导致的环流结构变异叠加在背景环流场之上,会显著影响粤东陆架边缘上升流的空间结构及强度.
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| 关 键 词： | 物理海洋学 上升流 内潮 陆架边缘 临界反射 广东海域 |
A preliminary study of the internal tide in the summertime upwelling regime off the Guangdong shelf edge in 2002 and its local feedback |
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| PAN Ai-jun
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LI Li
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GUO Xiao-gang
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XU Jin-dian.A preliminary study of the internal tide in the summertime upwelling regime off the Guangdong shelf edge in 2002 and its local feedback[J].Journal of Oceanography In Taiwan Strait,2012,31(2):151-159. |
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| Authors: | PAN Ai-jun LI Li GUO Xiao-gang XU Jin-dian |
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| Institution: | (Third Institute of Oceanography,SOA,Xiamen 361005,China) |
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| Abstract: | In situ temperature,salinity and ocean current data obtained from the repeated surveys by the ＂Chinese Coastal Circulation Formation and Variation Mechanism,Numerical Prediction and its Impacts on the Environment Program＂ in summer 2002 were combined with the concurrent satellite remote sensing observations（wind,SST and sea surface dynamic height） to conduct a preliminary investigation of the internal tide phenomena and its local feedback features in the traditional summertime upwelling regime off the Guangdong shelf edge.Significant and intermittent upwelling with relatively cold temperature perpendicular to the continental slope can be identified off the Guangdong shelf edge,which occurs largely at about 50～150 m depths for the A cruise（18～23℃） and deeper than 150 m depth for the B cruise（18℃）,respectively.Surface winds variations or the ocean dynamic height cannot explain the differences between the two cruises because surface winds variations are insignificant,and ocean eddies are relatively steady from weeks to months,and most importantly,influences of ocean eddies on current fields are apparently confined within the upper ocean shallower than 75 m. Further analysis indicates the existence of significant internal tide in the upwelling region off the Guangdong shelf edge.Although the present data fail to determine the nature of the internal tide precisely,the repeated survey profiles confirm the existence of the 1st and 5th mode internal tide which have different impacts on the thermal structure and circulation pattern in the upper ocean.The low-mode internal tide leads to sharp vertical fluctuations of the isotherms（30 m） adjacent to the maximum horizontal temperature gradient and current reversions on both sides of the thermocline.By contrast,the high-mode internal tide results in repeated reversions of the onshore current in the vertical direction,and the strong shear may lead to enhanced mixing.The internal tide transformation from the low-mode to the high-mode may be induced by the ＂critical reflection＂ effect since the bottom slope is closer to the ray slope.Further analysis suggests that if the current variability induced by different internal tide modes is superimposed on the background circulation,the summertime upwelling pattern and its intensity off the Guangdong shelf edge tends to be altered. |
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| Keywords: | physical oceanography upwelling internal tide shelf edge critical reflection Guangdong sea area |
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