IOCAS-IR  > 海洋环流与波动重点实验室
反向动能级串的全球分布特征,各向异性特征及其在涡平衡过程中的作用
王世红
学位类型博士
导师庞重光
2016-05
学位授予单位中国科学院大学
学位授予地点北京
学位专业物理海洋学
关键词能量级串 中尺度涡 线性斜压不稳定 涡特征尺度
摘要海洋观测表明,海洋中90%的动能以遍布大洋的中尺度涡形式存在,这些水平尺度从几十公里到几百公里不等的涡旋普遍存在于绝大部分海域。而中尺度涡的产生过程和平衡过程仍是值得探讨的问题。卫星高度观测到的反向动能级串级串为理解中尺度涡的发展平衡过程提供了一个新的视角。本文使用多种数据集对反向动能级串的全球分布特征,随深度的变化特征和各项异性特征进行了研究,以期对反向动能级串及其在涡平衡过程中的作用有一个更深刻的认识。论文主要结果如下:
一、利用卫星高度计海平面高度数据,结合涡分辨率的模式输出数据和再分析数据,讨论了反向动能级串的全球分布特征,特别是反向动能级串的振幅,能量注入尺度和反向传递的动能开始捕捉的尺度。发现在赤道外地区,反向动能级串是普遍存在的,其主要分布100-500km的尺度带上,其振幅和特征尺度表现出显著的区域差异性。
二、通过将局地线性斜压理论的预测结果以及观测到的中尺度涡场特征与反向动能级串的特征尺度进行对比,发现反向传递的涡动能主要来源于斜压不稳定过程释放的有效位能,而非线性的反向动能级串将该涡动能向更大尺度传递,对涡动能重新进行分配,并最终达到一个统计稳定状态。即反向动能级串是架起线性理论预测的涡特征尺度和实际观测到的涡特征尺度之间“gap”的桥梁。
三、通过诊断反向动能级串随深度的变化特征和各向异性特征,探究反向传递的动能的汇。初步结果表明,在高涡动能的东向强流系,一部分反向传递的动能向下传递。与此同时,一部分反向传递的动能转化为纬向平均流的动能。然而两种能汇各自的贡献仍有待于进步研究。
四、使用反向动能级串研究的相关方法,探究了黑潮延伸体区域中尺度涡场的年代际变化特征和产生机制。结果表明,斜压不稳定不是黑潮延伸体中尺度涡场年代际振荡的控制机制,正压不稳定对中尺度涡场的年代际振荡有积极的贡献。而非线性反向动能级串在决定黑潮延伸体中尺度涡场的空间特征方面起了决定性作用。
其他摘要Satellite altimetric observations of the ocean surface reveal a circulation dominated by turbulent flow on scales from tens to hundreds of kilometers, the oceanic mesoscale. mesoscale eddies contains ninty per cent of the kinetic energy of the global ocean. But how these eddies are generated and what sets their equilibrated scale remain open questions. The oceanic inverse kinetic energy cascade from satellite altimetry may provide a new perspective to understand these processes deeply. In this study, we use different data sets to diagnose the geographic character, depth dependence, and anisotropy of the inverse kinetic energy cascade so that we can have a more detailed and comprehensive understanding of the inverse cascade. Meanwhile, it will deepen our understanding of the generation and evolution of the mesoscale eddy. Major findings are listed as follows:
1.  The geographic character of the inverse cascade are analyzed based on the spectral kinetic energy flux calculated in the global ocean, using sea surface height (SSH) data from satellites, reanalysis data, and model outputs, with focusing on the amplitude and characteristic scales. A ubiquitous inverse cascade was also found at about 100–500 km scales outside the equatorial band , which varies greatly among different regions.  
2. There is a close agreement between and the spatial scale predicted by local linear baroclinic instability outside the tropical band, which indicates that the baroclinic instability is the major source of the upscale kinetic energy. Most of the eddy kinetic energy (EKE) comes from the available potential energy (APE), then the EKE is upscale transferred from scales near to the deformation radius to larger scales to maintain a statistical equilibrium state of the ocean. That is the inverse kinetic energy cascade is able to bridge the gap between the linear theory and the observations.
3. We also diagnose the depth dependency and the anisotropy of the inverse linetic energy cascade to explore the possible “sinks” of the upscale kinetic energy. The results show that a part of the upscale energy is transferred down the water column, reducing the surface expression and decreasing the signal seen by the altimeter in highly energetic predominantly eastward-flowing currents. Meanwhile, a part of the upscale energy will finally induce zonal jets. However, the contribution of each possible sink is still unclear in our study.
4. We further used above methods to explore the decadal modulation of the eddy field in the Kuroshio Extension. Our results show that he local linear baroclinic instability is not the dominant mechanism controlling the decadal modulation of the mesoscale eddy field in the upstream region. while, the barotropic instability makes a positive contribution to the decadal modulation of the mesoscale field. The observed eddy field is the result of an inverse cascade, and cannot be understood by linear theory alone.
学科领域物理海洋学
语种中文
文献类型学位论文
条目标识符http://ir.qdio.ac.cn/handle/337002/117015
专题海洋环流与波动重点实验室
作者单位1.中国科学院海洋研究所
2.中国科学院大学
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王世红. 反向动能级串的全球分布特征,各向异性特征及其在涡平衡过程中的作用[D]. 北京. 中国科学院大学,2016.
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