IOCAS-IR  > 海洋环流与波动重点实验室
印尼海及太平洋深层关键通道的溢流动力过程和混合分析
Alternative TitleHydraulic control and turbulent mixing of deep overflows in key passages of the Indonesian Seas and Pacific Ocean
谭舒文
Subtype博士
Thesis Advisor袁东亮
2020-08-21
Degree Grantor中国科学院大学
Place of Conferral中国科学院海洋研究所
Keyword印尼贯穿流 深层经向翻转环流 水力控制 湍流混合
Abstract

本篇论文针对地形影响狭窄通道溢流的动力过程开展资料诊断和理论研究,对印尼海及太平洋深层关键通道的底层溢流进行了个例分析,在海峡地形对深层环流动力特征及混合的影响方面取得了创新性的成果。首先,基于海洋观测,对利法马托拉海峡(Lifamatola Passage,简称利法海峡,位于赤道附近)的印尼贯穿流(ITF)深层分支的水动力特征开展了诊断分析;在此基础上,将不考虑地转的、计算连通海盆的单一海峡溢流流量的堰流公式拓展到了考虑地转的、多通道连接海盆的情形,并应用到了南太平的萨摩亚海峡(Samoan Passage,位于8ºS)。还通过水文观测数据对利法海峡内溢流的混合进行了定量估算,并结合数值模式与经典理论对萨摩亚海峡内溢流的不稳定性进行了分析。

基于历史潜标观测和理论分析,本文首次阐明利法海峡溢流具有水力控制特征。使用传统的、无地转效应的、不同海峡横截面形状(矩形、抛物线形、三角形)的溢流流量计算公式,即所谓“堰流公式”,对溢流的体积通量进行估算。然后,使用现场水文断面观测资料说明利法海槛下游存在强混合区域,通过Thorpe scale估算溢流层内每0.2平均的垂向扩散系数在2.3-10.1×10-3 m2 s-1。通过体积守恒和热力学平衡分析,指出混合对上层水体的卷挟使得溢流流量相比海槛附近流量的2.4 Sv,在下游放大0.6-1.2 Sv;估算下游封闭海盆(班达海,Banda Sea)的空间平均垂向扩散系数为1.6±0.5×10-3 m2s-1

推导了地转效应影响下位势涡度为常数的连接海盆的多海峡溢流的“堰流公式”,可以在不直接测量流速的情况下,对西边界流区域狭窄海峡内的溢流流量进行估算。使用该修正的堰流公式估算深层西边界流在萨摩亚海峡的流量为3.3-7.4 Sv,与实测的年平均流量(5.4 Sv)相近。该堰流公式在海峡溢流受到水力控制(如萨摩亚海峡)但是东侧海底高原/岛屿以东海流不受水力控制(如马尼希基海底高原,Manihiki Plateau)的情况下具有普适性可用于重要的大洋深层西边界流的估算(如北大西洋的丹麦海峡和法罗海台水道、大西洋洋中脊和西南太平洋的群岛通道等)。指出要维持海峡内部溢流的水力控制,海底高原/岛屿以东西边界流沿边界由于底摩擦耗散的能量必须与海峡中水跃区域内湍流混合耗散的能量相当。

Other Abstract

The hydraulics, instability, and mixing of two deep strait flows are investigated theoretically and numerically based on observation, in an attempt to provide insights into understanding the influence of topography on the deep circulation and on the spatial distribution of mixing. The two study subjects include the deep branch of Indonesian Throughflow (ITF) passing the Lifamatola Passage and the Antarctic Bottom Water (AABW) entering the Samoan Passage. Historical mooring and recently obtained in-situ hydrographic observations suggest that the Lifamatola Passage overflow is hydraulically controlled, based on which various “weir” formulae (i.e., estimating volume transport from stratification for cross-sections in different shapes) for non-rotating strait flows are employed and validated by observation. Hydraulic jump-like features, intense mixing, and entrainment (transport of 0.6-1.2 Sv) due to the presence of a hydraulically controlled overflow (transport of 2.4 Sv) are found in the lee of the sill. Thorpe-scale based estimates of diapycnal diffusivity coefficients averaged over downstream sites range from 2.3×10-3 m2 s-1 to 10.1×10-3 m2 s-1 within the overflow layer. The knowledge of strait flow transport and potential enthalpy flux allows estimating a bulk diapycnal diffusivity coefficient (1.6±0.5×10-3 m2s-1) in a closed basin downstream (i.e., Banda Sea). The critical condition for rotating strait flows with uniform potential vorticity (i.e., an extension to Gill, 1977) are derived to predict the volume flux through multiple passages, at least one of which is located on the pathway of an ocean boundary current. The formulations have been applied to predicting the transport distribution of the Deep Western Boundary Current (DWBC) within the Samoan Passage and east of the Manihiki Plateau. However, these formulae are valid only when the throughflow (e.g., flow through the Samoan Passage) is hydraulically controlled while the bypass flow (e.g., flow to the east of the Manihiki Plateau) is uncontrolled. Such a steady state is possible if, along the plateau, the energy dissipation due to hydraulic jumps in the passage can be balanced by the dissipation due to viscous forces (e.g., bottom frictions) in the bypass flow.

Subject Area海洋科学
MOST Discipline Catalogue理学::海洋科学
Language中文
Table of Contents

1  引言... 1

1.1  研究意义... 1

1.2  研究内容... 2

1.3  经向翻转环流的研究进展... 4

1.4  水动力学在地球流体中的应用进展... 6

2  利法海峡溢流的动力特征... 13

2.1  研究背景... 15

2.2  数据和方法... 16

2.2.1  潜标观测资料... 16

2.2.2  水文观测资料... 17

2.2.3  堰流公式推导... 17

2.2.4  层结流体中波动的解析解... 21

2.2.5  垂直模态求解... 23

2.3  利法海峡溢流流量估算... 24

2.4  水力控制诊断... 26

2.5  堰流公式应用... 28

2.6  直接内波诊断... 28

2.7  小结... 33

3  利法海峡溢流的混合特征... 37

3.1  研究背景... 37

3.2  数据和方法... 39

3.2.1  Thorpe尺度参数化求混合... 39

3.2.2  控制体积积分... 41

3.2.3  WOCE水文观测集... 44

3.3  利法海峡溢流的水文结构... 44

3.4  利法海峡溢流的混合估算... 45

3.5  利法海峡溢流的卷挟估算... 49

3.6  班达海上升、混合及湍流热通量估算... 50

3.7  不稳定分析... 51

3.8  小结... 54

4  地转效应影响下的堰流公式推导及应用... 57

4.1  研究背景... 57

4.2  两种海峡断面公式... 60

4.2.1  矩形海峡堰流公式... 61

4.2.2  抛物线形海峡堰流公式... 66

4.3  西边界流区域狭窄海峡内溢流水力控制机制... 69

4.3.1  非线性的约化重力数值模式... 70

4.3.2  理论解释... 73

4.4  萨摩亚海峡溢流的水动力学研究... 77

4.5  剪切流不稳定与中尺度涡旋... 79

4.6  小结... 82

5  总结与展望... 83

5.1  总结... 83

5.1.1  利法海峡溢流动力特征... 83

5.1.2  利法海峡溢流混合特征... 84

5.1.3  萨摩亚海峡溢流动力特征... 84

5.2  创新点... 85

5.3  工作展望... 85

参考文献... 87

  ... 97

作者简历及攻读学位期间发表的学术论文与研究成果... 99

Document Type学位论文
Identifierhttp://ir.qdio.ac.cn/handle/337002/164788
Collection海洋环流与波动重点实验室
Recommended Citation
GB/T 7714
谭舒文. 印尼海及太平洋深层关键通道的溢流动力过程和混合分析[D]. 中国科学院海洋研究所. 中国科学院大学,2020.
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