黑潮在吕宋海峡的形变及动力机制

根据１９９０年以来对吕宋海峡和中国南海（ＳＣＳ）北部的ＷＯＣＥ水文资料和其它海洋调查资料的分析，以及对同一海区的卫星遥测海表温度（ＳＳＴ）的资料处理，推断在吕宋海峡常年存在黑潮路径弯曲，西折进入ＳＣＳ并又流出ＳＣＳ的现象，作者将黑潮的这种变形称为“黑潮流套”。黑潮变形进入ＳＣＳ的位置在冬季位于海峡中部、南部附近，范围较大；在夏季略向北移，较集中于海峡中部，范围较小。作者认为，黑潮流套现象可用位涡守恒理论作定性的解释：当黑潮在吕宋海峡失去西边界支持后，其流轴以西贴近西边界的一部分流体，因具有较大的相对正涡度，会脱离黑潮主体在南海东北部形成反时针旋转或顺时针旋转的环流，而黑潮主体会以顺时针旋转的形式在海峡以西的海域出现。整个黑潮以弯曲、扩展的形式在海峡处产生形变，在海峡东侧出现反气旋涡旋的倾向。吕宋海峡黑潮流套及南海北部的诱生环流之流型，会因黑潮本身以及副热带环流整体的变化而变化，也与海峡的宽度有关。总之，吕宋海峡黑潮流套的形成是由当地特殊的地形条件和地转β效应这些内部机制决定的，它的常年存在有其必然性     

热带气旋影响吕宋海峡输运的研究进展与展望

吕宋海峡是连接南海与西太平洋的唯一深水通道,也是调节南海环流及其热力特征的关键海洋通道。在大尺度西边界流、中尺度涡、热带气旋等众多因子的共同影响下,吕宋海峡输运表现出显著的多时间尺度变率特征,其中热带气旋是影响该海域强烈且频繁的天气过程之一,解析吕宋海峡输运与热带气旋之间的动力联系也是近年来南海海洋研究的热点之一。本文主要从吕宋海峡附近热带气旋活动特征及其对黑潮、吕宋海峡附近环流结构、吕宋海峡输运的影响等方面回顾最新的研究进展。最后,本文认为接下来应当在热带气旋调制吕宋海峡输运的机制,以及对吕宋海峡输运年际变化的贡献等方面加强研究。     

吕宋海峡流场季节变化的数值模拟

基于海洋模式HYCOM(Hybrid Coordinate Ocean Model),利用大小区嵌套技术,分别对全球海洋和西北太平洋进行了网格嵌套数值模拟,研究了吕宋海峡海域环流场的季节性变化。考虑全球海洋环流影响的西北太平洋模式,成功地刻画了黑潮的流结构及季节变化。吕宋海峡海洋环流流场在不同深度处差异较大,存在着明显的季节变化。黑潮入侵南海主要发生在500m深度以上,冬季最明显,夏秋两季不明显。在500m层常年存在一支南海暖流流入西北太平洋,在800m层南海暖流消失。一年四季黑潮主要通过吕宋海峡的南部和中部进入南海。1 000m层流场表明,黑潮主要通过吕宋海峡的中部入侵南海。在800~1 000m处主要是黑潮水流入南海。     

潮汐对吕宋海峡附近海域环流结构的影响

为了考察潮汐混合效应对吕宋海峡附近海域环流场的影响,本文使用ROMS区域海洋模式,通过无潮实验与有潮实验的对比分析指出,潮汐混合作用可以影响121°E断面上的水交换和120d平均的纬向流速分布;在模拟时段内加入潮汐后,模拟结果中台湾岛西南的反气旋涡强度大幅减弱,贴近黑潮东侧的涡旋强度明显强于无潮实验,证明潮汐作用可以引起吕宋海峡海洋环流场较大的改变,特别对黑潮以"跨隙"路径通过吕宋海峡有贡献。     

热带气旋过境期间黑潮流轴变化的初步分析

利用卫星高度计资料分析了热带气旋"艾碧"(Abe,9315)、"贝姬"(Becky,9316)、"莫拉克"(Morakot,0309)和"茉莉"(Melor,0319)对吕宋海峡及其附近海域黑潮流轴的影响。研究表明:1)吕宋海峡附近海域黑潮流轴容易受到热带气旋的影响而发生一定的变化。2)在热带气旋的作用下,黑潮流轴因中尺度涡的变异而变化;当吕宋海峡东侧的暖涡西移时,将使黑潮的流轴向西弯曲,有利于黑潮在该处的入侵。     

2008年8—9月份吕宋海峡西南侧锚定ADCP的斜压海流观测

2008年8月份在吕宋海峡西侧大约4000m深的海域首次布放了两套深水潜标,对上层海洋进行了为期一个月的高频率ADCP海流采样。对数据进行了多重处理,分解得到平均流和逐层潮流,并分析了具有斜压性海流的频率分布。调和分析结果表明,该海域以不规则日周期潮流为主,潮流椭圆随深度旋转。海流的功率谱分析表明,内潮能量在温跃层附近最大,并随深度减小,同时海流有明显的近惯性振荡信号。该观测为了解吕宋海峡深层海洋的潮流、近惯性运动以及海峡水交换提供了第一手的资料。     

吕宋海峡海洋环流的基本特征

根据对高分辨率的并行海洋气候模式输出的较长时间序列的海面高度（ＳＳＨ）场的分析,推断在吕宋海峡附近海区常年存在吕宋海峡黑潮流套,该流套出现于吕宋海峡的中部和北部,表现为一个舌状的ＳＳＨ的高值中心自海峡东部的太平洋向西扩展到南海北部,大致到达１１０°Ｅ的位置,但其位置、形状、强度等表现季节变化,年际变化和季节内时间尺度变化的特征。在吕宋海峡东侧的大洋上,经常出现位置和范围时有变化的反气旋涡,与之对应,在ＳＳＨ的月平均经向和纬向剖面上,吕宋海峡东侧的大洋上有永久存在的ＳＳＨ高值中心。另外在１９９５年１～７月期间有一次完整的黑潮流环脱离黑潮主体并在南海北部向西南方向移动的过程。     

吕宋海峡上层海洋对于台风南玛都响应的观测分析与数值模拟试验

利用海洋模式POM模拟了吕宋海峡上层海洋对历经其上的2011年8月1111号台风南玛都的响应过程。基于2个方面进行了模拟实验,其一是吕宋海峡上层海洋对固定大小及位置的台风风场响应;其二是吕宋海峡上层海洋对台风南玛都移动期间的响应。并分析了台风南玛都的风场和海洋响应南玛都的表层流场、SST及SSS。研究结果表明:(1)吕宋海峡上层海洋对台风风场结构不对称的响应表现出吕宋海峡上层海洋右侧的流速要远大于左侧,海流和台风一样具有右偏特征。海洋表面温度(SST)下降2~7℃,下降的空间范围直径在百公里,表现为右强左弱的不对称性。(2)上层海洋对驻台风的响应过程中,海洋流场及SST达到能量的极值后,会触发1个反气旋流场控制吕宋海峡,SST经过约10d时间恢复到初始态。(3)上层海洋对台风移动过程的响应表现为1个随台风移动的海洋流场,海流的强度和SST下降的幅度都较小,海流气旋式结构沿着路径有一定的拉伸,并且在路径后方出现尾流。     

混合坐标模式HYCOM模拟COADS强迫下的南海平均环流

采用混合坐标模式(HYCOM)模拟南海环流,同时利用海表温度卫星资料和吕宋海峡Sb-ADCP观测海流数据来评估模式结果.地形敏感性实验表明,吕宋海峡地形数据对模拟黑潮入侵方式影响较大,在地形误差较大的情况下,模拟的黑潮可能以反气旋流套方式入侵.和Pathfinder海表温度卫星资料比较,模式输出的月平均温度在海盆区域误差较小.ERA-15资料强迫所模拟的吕宋海峡上层环流和Sb-ADCP观测一致,而COADS结果低估了吕宋海峡的体积输送.     

基于LLC4320环境数据的吕宋海峡声学特征分析

声波是水下信息获取和目标探测的主要手段,其在海洋波导中的传播特性及声场分布与海洋动力环境紧密相关。基于LLC4320再分析数据,针对吕宋海峡及其周边海域,开展了局部环境场特征和声学特征分析,评价了高分辨率数据对于声学特征研究的适用性。首先,通过分析该区域1月温盐场的时间和空间变化特征,结合跃层的空间分布和时间变化,研究了吕宋海峡区域的动力环境特征;其次,开展了声传播规律的研究,并评价了声速、声传播特征等与温盐场的相关性,可为高分辨率的海洋数值模拟在海洋声学特征研究中的应用提供参考。     

Developments in ocean climate modelling

This paper presents some research developments in primitive equation ocean models which could impact the ocean component of realistic global coupled climate models aimed at large-scale, low frequency climate simulations and predictions. It is written primarily to an audience of modellers concerned with the ocean component of climate models, although not necessarily experts in the design and implementation of ocean model algorithms.     

Turbulent dispersion in the ocean

The mathematical framework for turbulent transport in the ocean is reasonably well established. It may be applied to large-scale fields of scalars in the ocean and to the instantaneous or continuous discharge from a point. The theory and its physical basis can also provide an interpretation of passive scalar spectra. Spatial variations in the rate of turbulent transfer can be related to the movement of the center of mass of a scalar and to a formulation in terms of entrainment. The relative dispersion of a scalar with respect to its center of mass and the streakiness of the concentration field within the relative dispersion domain need to be considered. In many of these problems it is valuable to think in terms of simple models for individual streaks, as well as overall statistical properties.     

Circumpolar connections between Antarctic krill (Euphausia superba Dana) populations: Investigating the roles of ocean and sea ice transport

Antarctic krill, Euphausia superba Dana, has a heterogeneous circumpolar distribution in the Southern Ocean. Krill have a close association with sea ice which provides access to a critical food source and shelter, particularly in the early life stages. Advective modelling of transport pathways of krill have until now been on regional scales and have not taken explicit account of sea ice. Here we present Lagrangian modelling studies at the circumpolar scale that include interaction with sea ice. The advection scheme uses ocean velocity output from the Ocean Circulation and Climate Advanced Modelling (OCCAM) project model together with satellite-derived sea ice motion vectors to examine the potential roles of the ocean and sea ice in maintaining the observed circumpolar krill distribution. We show that the Antarctic Coastal Current is likely to be important in generating the large-scale distribution and that sea ice motion can substantially modify the ocean transport pathways, enhancing retention or dispersal depending upon location. Within the major krill region of the Scotia Sea, the effect of temporal variability in both the ocean and sea ice velocity fields is examined. Variability in sea ice motion increases variability of influx to South Georgia, at times concentrating the influx into pulses of arrival. This variability has implications for the ecosystem around the island. The inclusion of sea ice motion leads to the identification of source regions for the South Georgia krill populations additional to those identified when only ocean motion is considered. This study indicates that the circumpolar oceanic circulation and interaction with sea ice is important in determining the large-scale distribution of krill and its associated variability.     

海洋投弃式温深剖面仪应用发展概述

海洋温度的变化会显著影响水下声传播、生物活动、气象和洋流等现象,温深是反映海洋变化运动规律的基本参数。投弃式温深剖面仪（Expendable Bathythermograph,XBT）、温盐深测量仪（Conductivity Temperature Depth,CTD）、全球海洋实时观测网（Array for Real-time Geostrophic Oceanography,Argo）等是目前进行海水温深测量的主要仪器。其中XBT因其现场测量简便、效率高、硬件成本低等特点,正在被大规模使用。本文主要介绍有关海洋温度测量的背景及演化历史,分析对比了国内外相关仪器设备的发展现状,总结了国产化产品还存在的差距和不足,另外对传感器、结构设计、数据通讯传输、数据后处理、可靠性研究等关键技术和研究热点进行了详细介绍,最后对未来无人平台的技术发展路线给出了思路和见解,开展投弃式温深剖面仪的相关技术研究和产品研制对实现国产化有积极的推动意义。     

Numerical simulations of the Mediterranean sea outflow: impact of the entrainment parameterization in an isopycnic coordinate ocean model

Gravity current entrainment is essential in determining the properties of the interior ocean water masses that result from marginal sea overflows. Although the individual entraining billows will be unresolvable in large-scale ocean models for the foreseeable future, some large-scale simulations are now being carried out that do resolve the intermediate scale environment which may control the rate of entrainment. Hallberg [Mon. Wea. Rev. 128 (2000) 1402] has recently developed an implicit diapycnal mixing scheme for isopycnic coordinate ocean models that includes the Richardson number dependent entrainment parameterization of Turner [J. Fluid Mech. 173 (1986) 431], and which may be capable of representing the gravity current evolution in large-scale ocean models. The present work uses realistic regional simulations with the Miami Isopycnic Coordinate Ocean Model (MICOM) to evaluate ability of this scheme to simulate the entrainment that is observed to occur in the bottom boundary currents downstream of the Mediterranean outflow. These simulations are strikingly similar to the observations, indicating that this scheme does produce realistic mixing between the Mediterranean outflow and the North Atlantic Central Water. Sensitivity studies identify the critical Richardson number below which vigorous entrainment occurs as a particularly important parameter. Some of these experiments also show meddies detaching from the Mediterranean undercurrent at locations that appear to be highly influenced by topographic features.     

Intrayear Variability of Geostrophic Zonal Currents in the Tropical Zone of the South Atlantic

On the basis of the results of calculation and analysis of the characteristics of space variability of the geostrophic component of large-scale zonal currents in the tropical zone of the South Atlantic, its intrayear oscillations, and the components of tangential wind stresses, we establish the regularities of seasonal variability of the system of gradient currents on the ocean surface depending on wind conditions. We describe the specific features of seasonal meridional fluctuations of the midstreams of the geostrophic component of zonal large-scale currents and the intrayear variations of their velocity.     

Transformation of the Level of Barotropic Ocean under an Elliptic Region of Disturbances of a Baric Field

We study elevations of the level of a homogeneous ocean caused by a large-scale elliptic anomaly of the field of atmospheric pressure and determine the conditions under which Earth's rotation and the asymmetry of the region of disturbances of the baric field lead to significant deviations of the ocean level from its values given by the law of inverted barometer. Our investigation is based on the numerical analysis of the integral solution of the linear problem. It is shown that the deviations from the law of inverted barometer are especially pronounced in shallow-water regions, at high latitudes, and for strongly asymmetric regions of disturbances of atmospheric pressure.     

一种基于表面状态参数的三维海洋动力学模型数值求解方法*

大面积的海洋表面实时运动状态可以通过遥感技术获取, 而海洋内部的运动状态只能进行定点观测, 无法达到大面积的实时监测。基于海洋动力学基本原理, 在正压浅海大陆架模式下, 在三维空间构建海洋表面与内部运动状态的关系模型; 利用遥感探测的海洋表面流速与流向数据, 结合海域的浪高、风速状态参数, 运用有限差分法反演出深层海流的流速与流向信息。反演结果符合海洋动力学规律, 反映出了深层流整体分布状态, 扩展了雷达遥感应用范围。     

Effects of the deep ocean circulation on the reservoir characteristics of the ocean

To examine the effects of the deep ocean circulation on the characteristics of the ocean as a reservoir, age distributions of the material whose source and sink are at the ocean surface are calculated using an idealized vertical two-dimensional model of the ocean. The results show that the large-scale vertical circulation of the deep water accelerates the renewal of deep water and reduces the average age of the material. It is also shown that the multi-layered structures of the deep circulation are more realistic than the one-layered structure and promote the renewal of the deep water.     

Observational and laboratory insights into salt finger convection

Improving observational capabilities in the ocean are revealing a substantial body of evidence that the double-diffusive instability known as salt fingers is widely present and plays a significant role in oceanic mixing. This evidence includes unique fine- and microstructure features in particular regions and distinct patterns in the temperature and salinity variations over large areas. Laboratory experiments have also advanced our understanding of salt fingers. The insights gleaned from both laboratory and ocean are reviewed and related to large-scale ocean structure and climate modeling.