3～5月份东印度洋上层水文要素特征分析

利用中国科学院"实验1"号调查船2010~2012年东印度洋3个航次的走航断面观测数据,分析了春季孟加拉湾南部和赤道东印度洋上层海洋的水文结构特征,同时结合卫星遥感资料和世界海洋图集2009(world ocean atlas 2009,WOA09)气候态温、盐资料,探讨了孟加拉湾南部海水经向地转输运的变化以及温跃层的波动。结果表明,在3~5月份,即印度洋冬季风向夏季风转换期间,赤道西风的爆发成为这一海域最关键的驱动力,将阿拉伯海的高盐水向东输运,使赤道纬向压强梯度力转为西向,减弱了赤道潜流并引起向北的经向地转输运。在孟加拉湾湾口,赤道的波动强迫导致了经向输运由南向转为北向,来自阿拉伯海的高盐水与孟加拉湾的低盐水在此汇集,形成了明显的盐度梯度;波动强迫还使得孟加拉湾湾口呈现出一个向西移动并减弱的气旋涡流场。在波动和表层盐度差异的影响下,湾口温跃层维持着向西下倾斜的状态,即使是在印度洋东岸海水堆积时,也没有显示出如赤道断面温跃层那般的大幅度加深。     

冬季黄海暖流的诊断计算

采用ECOMSED三维水动力模式，诊断计算了冬季渤海、黄海和东海的近海环流状况，重点分析了黄海暖流的演变过程及其垂直结构，并探讨了黄海暖流的形成机理。结果表明，黄海暖流于12月初步形成，次年2月发展最强盛，3月开始衰退。黄海暖流在表层和次表层（0-30m）并不是一支持续稳定的流，其持续稳定性仅在近底层得到很好的体现。对黄海暖流形成机理的分析表明，压强梯度力、垂向摩擦力和柯氏力占主要地位。在表层及次表层，主要表现为风的正压作用，而在近底层，则由海平面起伏造成的正压梯度力和密度场引起的斜压梯度力形成的总压强梯度力与柯氏力基本平衡，因而黄海暖流可基本认为是准地转流。     

台风移速突变的诊断分析及路径预报

本文利用台风移动方程对作用在台风上的各力进行了诊断分析：主要力是气压梯度力和地转偏向力，二者同量级，其他各力约小１－３个量级；当台风加速移动时，气压梯度力小于地转编向力；减速移动时，气压梯度力大于地转偏向力。用预报方程计算得到的台风路径与实际台风路径在趋势上近于一致，预报误差约为２００ｋｍ。     

太平洋海域赤道潜流的研究综述

赤道潜流在1952年由克伦威尔发现,并命名为克伦威尔流。随后许多海洋学家对赤道潜流进行了研究,但其研究的重点是潜流与渔业的关系。20世纪80年代之后,El Nio和La Nina事件不断出现,对全球气候带来严重影响,人类对赤道潜流进行的研究开始增多,并深入探索赤道潜流的异常变化与El Nio事件的关系,取得了许多重要的进展。本文根据国内外对太平洋海域赤道潜流的主要研究成果,评述了有关赤道潜流的研究进展、存在问题及未来的发展方向。     

赤道太平洋西部的上层环流

讨论了赤道太平洋西部的上层海洋环流、结果表明：（１）棉兰老涡气旋式环流随着深度的增加而减小。由于埃克曼抽吸作用，它是一个低盐冷涡；（２）对棉兰老岛—巴布亚新几内亚岛之间穿越流的观测表明：该断而北部（５°—６°Ｎ）的Ｓ向流是棉兰老海流的Ｓ向延伸；Ｗ向的巴布亚新几内亚沿岸潜流可达该断而的东南部门（２°Ｎ一２°Ｓ）；北赤道逆流则在两者之间沿表层的盐度锋作Ｅ向流动。据此，赤道太平洋西部次表层盐度分布状况可得到圆满解释。关键词：     

ENSO相联系的热带太平洋上层海洋异常环流

本文使用SODA(simple ocean data assimilation)海洋同化资料,系统分析了厄尔尼诺-南方涛动(El Ni?o-Southern Oscillation,ENSO)循环中冷暖位相期间热带太平洋上层海洋环流的演变规律,探讨了形成海洋环流异常的新机制。结果表明,在厄尔尼诺成熟期,热带中东太平洋赤道潜流最弱,赤道两侧出现反气旋性环流异常;西太平洋赤道外热带海域出现气旋性环流异常,该区南、北赤道流、棉兰老流、黑潮、新几内亚沿岸潜流及南赤道逆流增强;北赤道逆流区出现异常气旋性环流串,北赤道逆流接近正常。在厄尔尼诺衰退期和拉尼娜发展期,热带中西太平洋赤道潜流达到极强,赤道两侧出现气旋性环流异常;西太平洋赤道外热带海域异常环流减弱,该处主要流场的强度减弱或处于正常状态;北赤道逆流区反转为异常西向流。结果表明, ENSO循环期间的上层海洋环流异常受到热带太平洋温跃层深度异常产生的压强梯度力异常调控,在赤道外热带海洋温跃层深度异常和科里奥利力共同作用产生大尺度海洋环流异常,而在赤道海域,海洋温跃层深度异常和Gill效应造成赤道潜流异常以及关于赤道对称的气旋或反气旋性环流异常。     

1993年冬季所罗门群岛─关岛断面地转流的初步分析

根据1993年1─2月“实验3”号考察船在霍尼亚拉港（瓜达尔卡纳尔岛）至关岛的断面观测的温、盐度资料，分析了该断面上的地转流结构，计算了南赤道流及北赤道逆流的地转流流速和流量。结果表明：在纬线方向上E向流与W向流呈带状分布，在垂向上也多为E向流与W向流交替出现。在南赤道流和北赤道逆流中都夹有与主流向相反的流动，它们的流量分别约占主流向流量的1／3和1／5。文章还将分析计算结果与手头掌握的文献报道的结果作了比较。     

1993年冬季所罗门群岛——关岛断面地转流的初步分析

根据１９９３年１－２月“实验３号”号考察船在霍尼亚接港（瓜达尔卡纳尔岛）至关岛的断面观测的温、盐度资料，分析了该断面上的地转流结构，计算了南赤道流及北赤道逆流的地转流流速和流量。结果表明：在纬线方向上Ｅ向流与Ｗ向于带状分布，在垂 也多为 流一Ｗ向流交替出现。在南赤道流和北赤道逆流中都夹有与主流上反的流动，它们的流量分别占向流量的１／３和１／５。文章还将分析计算结果与手头掌握的文献报道的结果作了比较     

中太平洋西部赤道流系的诊断计算

利用１９７９年“实践”号海洋调查船在１０°Ｓ—５°Ｎ，１７０°Ｅ—１７５°Ｅ海区的调查资料，对该海区的海流进行了诊断计算。计算结果表明：该海区存在北赤道逆流、南赤道流、南赤道逆流、赤道潜流和赤道中层流。另外，在赤道有一股强的上升流。由于该上升流的存在，使赤道潜流沿纬向发生弯曲：位于上升流西侧的潜流流轴降至３００ｍ水层深处，而东侧上升至１００ｍ左右的水层深处。此外，计算结果显示潜流核心位置并不正好位于赤道上，而是向北偏移约０．５°。在有实测海流的格点上，计算值与实测值基本一致。     

赤道西太平洋部分海域上层水的海洋化学

主要研究了菲律宾东南海域（区域Ｉ）和伊里安岛东部的北部海域（区域Ⅱ）上层水（０～１５０ｍ）化学参数ｐＨ，Ｅｈ，Ｅｓ，∑Ｓ（－Ⅱ）和ａ＾２－ｓ等的分布特征和－２价硫的产生机制，结果表明，该海域表层南赤道逆流和次表层的赤道潜流是影响化学参数特别是ＤＯ和∑Ｓ（－Ⅱ）的主要因素，高生产力与高水温是赤道西太平洋上层水中－２价硫产生与保存的重要影响因素，区域Ⅱ中的ｐＨ，∑Ｓ（－Ⅱ）ａ＾２－ｓ，ＤＯ比区域Ｉ高而     

印度洋赤道潜流年际变化特征及其与印度洋偶极子的联系

印度洋赤道潜流(equatorial undercurrent,EUC)是赤道流系的重要组成部分,对印度洋物质输运和能量交换有着重要意义.基于SODA 3.4.2海洋再分析数据,对印度洋EUC的三维空间结构和年际变化特征进行分析,并揭示其年际变率与印度洋偶极子(Indian Ocean dipole,IOD)的联系.结...     

The inversion of the Equatorial Undercurrent in the western tropical Pacific during 1986/1987 El Niño event

On the basis of time series measurements of winds, currents, temperature and salinity from equatorial current meter mooring and acoustic Doppler current profiler during the PRC/USA joint air-sea interaction studies in the western tropical Pacifc Ocean and sea level data provided by Prof.Wyrtki, analyses are made of the physical process and mechanism for the exceptionally inverse phenomenon (westward) of the Equatorial Undercurrent (EUC) in the western tropical Pacific after entering the mature stage of 1986/1987 ENSO event, and the numerical simulation is also conducted by "cross section" model.The results indicate that the inversion of the EUC is related to that of pressure gradient force near the equator under the influence of non-local permanent westerlies.     

Centrifugal forces estimated from trajectories of drifting buoys in winding paths of the Kuroshio

Radii and angular velocities in the motions of drifting buoys deployed in the Kuroshio are estimated by fitting circles to the trajectories of two drifting buoys, one with a drogue at 300 m depth and the other at 800 m depth. The buoys were deployed in the Kuroshio where it was flowing counter-clockwise around the large cold water mass south of Honshu. The same technique was applied to two drifting buoys with drogues at 300 m depth placed in the Kuroshio where it flowed clockwise around Oshima Island in Sagami Bay. The centrifugal forces were 7% and 6% as large as the Coriolis forces in the Kuroshio around the cold water mass, and they were –56% and –42% as large as the Coriolis forces in the current around the Oshima Island. The temperature gradient observed in the Oshima-West Channel suggested that the pressure gradient there was smaller due to the centrifugal force acting against the Coriolis force than the pressure gradient to be balanced with the Coriolis force.     

TOPEX/Poseidon and Jason Equatorial Sea Surface Slope Anomaly in the Atlantic in 2002: Comparison with Wind and Current Measurements at 23W

A time series of velocity profile in the upper 150 m of the equatorial Atlantic was gathered at 23W in 2002 within the PIRATA program. It constitutes the first time series of near surface current measurements simultaneous with altimetric data in the equatorial Atlantic. The surface slope anomaly along the equator is computed from satellite altimetry, and, as a proxy for the pressure gradient along the equator, compared with the wind and near surface current data. In a first step, a time series of the surface slope anomaly along the equator in the Atlantic is computed from the 10-year-long TOPEX/Poseidon sea level anomalies. A sensitivity study establishes the robustness of the calculation. Apart from a 15 cm bias, the equatorial sea surface slope anomalies estimated either from TOPEX/Poseidon or from Jason over the 6-month overlap (Feb.-Aug. 2002) do not reveal drastic differences. We produce two sea surface slope anomaly composite time series for 2002 (one with T/P data, the other with Jason data during the commissioning phase) and compare them to the wind and velocity data at 23W. As expected, the near surface velocity and depth of the upper limit of the equatorial undercurrent (EUC) are extremely well correlated with the surface pressure gradient anomaly. 10-year-long time series of altimetry-derived zonal sea surface slope anomaly and ECMWF ERA40 wind stress are also well correlated. They exhibit similar spectral content and similar anomalous years. This is a first step towards a full analysis of the EUC dynamics using altimetry, PIRATA data (near surface current and subsurface thermohaline structure) and model. These initial comparisons reinforce the utility of Jason measurements for continuing the 10-year and highly accurate TOPEX/Poseidon time series for study of equatorial signals.     

The rôle of the complete Coriolis force in cross-equatorial flow of abyssal ocean currents

Ocean currents flowing close to or across the equator are strongly constrained by the change in sign of f, the locally vertical component of the Earth’s rotation vector, across the equator. We investigate these currents using a shallow water model that includes both the locally vertical and locally horizontal components of the Earth’s rotation vector, thus accounting for the complete Coriolis force. We therefore avoid making the so-called “traditional approximation” that retains only the part of the Coriolis force associated with the locally vertical component of the rotation vector. Including the complete Coriolis force contributes an additional term to the fluid’s potential vorticity, which may partially balance the change in sign of f as fluid crosses the equator over suitably shaped bathymetry.We focus on the Antarctic Bottom Water, which crosses the equator northwards in the western Atlantic ocean where the local bathymetry forms an almost-zonal channel. We show that this bathymetry facilitates the current’s equatorial crossing via the action of the “non-traditional” component of the Coriolis force. We illustrate this process using both analytical and numerical solutions for flow of an abyssal current over idealised equatorial topography. We also consider the one-dimensional geostrophic adjustment of a body of fluid across the equator, and show that the “non-traditional” contribution to the fluid’s angular momentum permits a larger cross-equatorial transport. These results underline the importance of including the complete Coriolis force in studies of the equatorial ocean, particularly in the weakly-stratified abyssal ocean where the non-traditional component is most pronounced.     

TOPEX/Poseidon and Jason Equatorial Sea Surface Slope Anomaly in the Atlantic in 2002: Comparison with Wind and Current Measurements at 23W

A time series of velocity profile in the upper 150 m of the equatorial Atlantic was gathered at 23W in 2002 within the PIRATA program. It constitutes the first time series of near surface current measurements simultaneous with altimetric data in the equatorial Atlantic. The surface slope anomaly along the equator is computed from satellite altimetry, and, as a proxy for the pressure gradient along the equator, compared with the wind and near surface current data. In a first step, a time series of the surface slope anomaly along the equator in the Atlantic is computed from the 10-year-long TOPEX/Poseidon sea level anomalies. A sensitivity study establishes the robustness of the calculation. Apart from a 15 cm bias, the equatorial sea surface slope anomalies estimated either from TOPEX/Poseidon or from Jason over the 6-month overlap (Feb.–Aug. 2002) do not reveal drastic differences. We produce two sea surface slope anomaly composite time series for 2002 (one with T/P data, the other with Jason data during the commissioning phase) and compare them to the wind and velocity data at 23W. As expected, the near surface velocity and depth of the upper limit of the equatorial undercurrent (EUC) are extremely well correlated with the surface pressure gradient anomaly. 10-year-long time series of altimetry-derived zonal sea surface slope anomaly and ECMWF ERA40 wind stress are also well correlated. They exhibit similar spectral content and similar anomalous years. This is a first step towards a full analysis of the EUC dynamics using altimetry, PIRATA data (near surface current and subsurface thermohaline structure) and model. These initial comparisons reinforce the utility of Jason measurements for continuing the 10-year and highly accurate TOPEX/Poseidon time series for study of equatorial signals.     

中太平洋西部赤道潜流的水文分析

本文利用我国1979年1～2月和4～6月在中太平洋西部的考察资料,分析了赤道潜流区的温、盐分布及赤道潜流的流系特征,并给出了潜流区及其周围海区的流场结构。     

The seasonal variation of undercurrent and temperature in the equatorial Pacific jointly derived from buoy measurement and assimilation analysis

Based on the TOGA-TAO buoy chain observed data in the equatorial Pacific and the assimilation analysis results from SODA(simple ocean data assimilation analysis), the role of the meridional cells in the subsurface of the tropical Pacific was discussed. It was found that, the seasonal varying direction of EUC (the quatorial Undercurrent)in the Peacific is westwards beginning from the eastern equatorial Pacific in the boreal spring. The meridional cell south of the equator plays important role on this seasonal change of EUC.On the other hand, although the varying direction is westwards,the seasonal variation of temperature in the same region gets its minimum values in the boreal autumn beginning from the eastern equatorial Pacific.The meridional cell north of the equator is most responsible for the seasonal temperature variation in the eastern equatorial Pacific while the meridional cell south of the equator mainly controls the seasonal temperature change in the central Pacific. It is probably true that the asymmetry by the equator is an important factor influencing the seasonal cycle of EUC and temperature in the tropical Pacific.