1986—1987年El Ni■o事件前后西太平洋热带海域的上层热力结构

本文采用本所“实验3”号1985—1987年冬季在西太平洋热带海域考察的CTD资料,分析了1986—1987年E1 Ni(?)o事件前后西太平洋热带海域上层热力结构的时、空分布及演变特征。结果表明,该事件发生前的冬季,沿13°N,在124.5°—137°E存在海洋Rcssby波扰动,海洋上层热含量很丰富。该事件初期,沿5°N,在127°—135°E一带,有海洋赤道Kelvin波动。此时南、北赤道流均较弱。事件后期,海洋赤道Kelvin波扰动不明显,但南赤道流较强,且范围向北伸展。1986年10—12月,表征E1 Ni(?)o事件的上层热力结构首先在西太平洋海域出现,然后东传。1987年10—11月,表征非E1 Ni■o事件的上层热力结构率先在西太平洋热带海域西边界恢复。     

1985—1986年冬季热带西太平洋次表层热状况的分布特征

据海洋调查船“向阳红14”号和“向阳红16”号在1985年12月—1986年3月期间观测到的XBT及CTD资料分析了热带西太平洋1985—1986年冬季次表层热状况的分布特征。在1985—1986年冬季,热带西太平洋亦道附近海域,表层暖水比常年深厚,温跃层的纬向坡度比常年大。在130°E剖面上,8°N附近次表层等温线升高,这表明在太平洋西部,北赤道流及北赤道逆流比常年加强。这些海洋次表层热状况特征与Wyrtki等人指出的埃尔尼诺(El-Nio)事件发生前的热带西太平洋热状况相符。     

热带西太平洋主要流系的季节变化和年际变化

利用美国国家环境预报中心的太平洋海域１９８０～１９９５年四维同化资料,计算了棉兰老海流和与之有密切联系的北赤道流、北赤道逆流流量的年际变化和季节变化特征。由此得出以下结论：（１）棉兰老海流对北赤道逆流的初始流量贡献较大,是北赤道充的主要水源提供之一,棉兰老海流与黑湖在季节变化中存在反相关系;（２）棉兰老海流在厄尔诺年初期加强,在反厄尔尼诺期间减弱;（３）棉兰老海流的季节变化信号强于年际变化信号。     

热带西太平洋主要流系的季节变化和年际变化

利用美国国家环境预报中心的太平洋海域 1 980— 1 995年四维同化资料 ,计算了棉兰老海流和与之有密切联系的北赤道流、北赤道逆流流量的年际变化和季节变化特征。由此得出以下结论 :( 1 )棉兰老海流对北赤道逆流的初始流量贡献较大 ,是北赤道逆流的主要水源提供者之一 ,棉兰老海流与黑潮在季节变化中存在反相关系 ;( 2 )棉兰老海流在厄尔尼诺年初期加强 ,在反厄尔尼诺期间减弱 ;( 3)棉兰老海流的季节变化信号强于年际变化信号。     

1987及1988年夏季西北太平洋主流系和水位与大气环流关系的数值研究

用一个包括风应力项的二维绝热非线性数值模式计算分析了1987及1988年夏季北太平洋主流系和水位与大气环流的关系。将模拟的1987和1988年流场作比较可知:1987年南赤道流较弱,而北赤道逆流、北赤道流及北太平洋流较强,同时各流系位置也都偏南1—2个纬距;模拟的1987年黑潮及对马暖流也明显比1988年强。分析表明,1987年夏季南赤道流弱、北赤道逆流强的主要原因是该年东南信风弱,而北赤道流、黑潮及对马暖流较强则主要与该年12°—25°N之间较强的东风以及东海较强的南风有关。模拟结果可对管秉贤提出的夏威夷群岛附近风应力涡度与黑潮强度的统计关系给出一个动力学解释。根据1987及1988年夏季气压场及风场对比分析。可以认为1987年北赤道流、黑潮及对马暖流较强可能与1987El Nino年副热带高压较强有关。     

2015/2016年超强厄尔尼诺事件基本特征及生成和消亡机制

全球变暖背景下, 2015/2016年超强厄尔尼诺(El Ni?o)事件倍受关注, 此次事件是中部型和东部型El Ni?o的混合。研究发现, 西风爆发和北太平洋经向模态对触发此次事件均有所贡献。通过对比2015/2016年、1997/1998年与中部型事件可知, 2015/2016年事件在暖背景中产生, 其发展形态与中部型事件较为相似, 后期海表面温度异常迅速衰退主要与赤道东太平洋海域持续的东风异常以及纬向平流较弱有关。较之1997/1998年事件, 2015/2016年事件的海洋动力调整较弱, 表现为较弱的温跃层反馈和海洋波动, 纬向平流反馈的贡献大于温跃层反馈, 大气强迫影响显著, 中部海域相关要素异常值较大。在2015/2016年事件期间, 赤道海域以及近赤道海域海洋上层热含量的变化基本呈负相关, 且变化较为同步; 衰退阶段热含量的流失主要集中在5°S—5°N海域, 向两极的热输送明显。     

全球变暖背景下对太平洋环流（1960—1999）的模拟

我们用Non—Boussinesq POP海洋模式和NECP 1000 hPa的风应力和气温场资料，模拟了1960—1999年太平洋环流，结果显示：在过去的40年，热带太平洋环流变弱了，另外，由于全球变暖，由北赤道流产生的向热带西太平洋沿岸的热输送和由南赤道流产生的向南太平洋中高纬度的热输送随着时间是减弱的，而在北半球，由北赤道流产生的向中高纬度的热输送是增加的。     

一个耦合模式下北赤道流分叉的初步研究

利用一个全球海洋-大气耦合模式,对北赤道流分叉的季节、年际变化特征进行了初步研究.模式结果表明北赤道流的分叉纬度,在表层大约是15.2°N,随深度而向北移动,在1000m深度大约为20°N.北赤道流分叉在春、夏季节偏南,而秋、冬季节偏北,可能主要与局地的Ekman抽吸有关.北赤道流分叉的年际变化周期表现有准2年、3～4...     

印尼贯穿流出流海域海表高度时空变化

采用经验正交分解(Empirical Orthogonal Function,EOF)分析方法对印尼贯穿流出流海域卫星测高海面高度异常资料进行了分析,分析结果显示研究海域海面高度异常存在多时间尺度变化特征。1993—2013年期间,研究海域海面高度异常场存在明显的升高趋势,其升高速率为0.6 cm/a;研究海域海面高度异常存在显著的年际变化,其与Niño3.4指数的相关系数超前滞后相关最大可达0.65,且厄尔尼诺年偏高,拉尼娜年偏低;海面高度异常年周期变化显著海域主要受印尼贯穿流、印度洋南赤道流和Eastern Gyral Current(EGC)季节变化的影响,半年周期变化则对应于爪哇沿岸流与南赤道流共同作用下形成的涡旋的半年周期变化;另外,研究海域海面高度异常还存在显著的季节内变化特征。     

1964—1983年西太平洋北赤道流的变化特征

据西太平洋七个经向剖面上北赤道流南北界面上20℃等温线深度差(ΔD),分析了西太平洋北赤道流的平均季节变化和年际变化。并探讨了它与黑潮、北赤道逆流及埃尔尼诺之间的关系。各剖面上的ΔD平均变化曲线表明,西太平洋北赤道流平均强度自东向西增强。从ΔD距平值的时间经度剖面图中可以得出一些有趣的结果。例如,ΔD距平向西传播,并有与埃尔尼诺事件相一致的3—4年的变化周期;当日本南部黑潮大弯曲及埃尔尼诺事件发生时,西太平洋北赤道流强度均明显减弱;但对此两种不同的现象,北赤道流的减弱又有不同的特点。     

Distribution of Phyllosoma Larvae (Crustacea: Decapoda: Palinuridae,Scyllaridae and Synaxidae) in the Western North Pacific

Phyllosoma larvae were identified and their distribution was examined, based on the larvae in ichthyoplankton samples collected in the Japanese Eel Expedition to the spawning area of A. japonica in the western North Pacific from August 30 to September 13, 1986 (Leg. 1), and from September 22 to 25, 1986 (Leg. 2), on board the R/V Hakuho-maru. Phyllosoma larvae belonged to 3 families (Scyllaridae, Palinuridae and Synaxidae) representing 6 genera and 14 species. A total of 336 palinurid and synaxid phyllosoma larvae were collected, of which 233 larvae (about 70%) were identical with P. longipes s. l, while a total of 362 scyllarid phyllosoma larvae were collected, of which 274 larvae (about 76%) were identical with S. cultrifer. Phyllosoma larvae of P. longipes s. l and S. cultrifer showed a similar distribution to each other. The larvae were abundant in the water close to Mariana Islands, although late stage examples were abundant in waters of Luzon and eastern Taiwan. Distributions of these larvae may be related intimately with the North Equatorial Current existing along 15°N. The North Equatorial Current approaches the eastern coast of the Philippines and then separates into two branches of northward and southward flows. The northward flow contributes to generating the Kuroshio Current while the southward flow goes to generate the Mindanao Current. Judging from distributions of phyllosoma larvae in the present study, it is assumed that the larvae of the above two species may have been released in Mariana Islands and transported westward from there through the North Equatorial Current. These larvae may then be transported to eastern Taiwanese waters.     

137°E断面北赤道流、黑潮变异和黑潮大弯曲的关系

分析了１９７２～１９８８年１３７Ｅ断面资料,结果表明,北赤道流和黑潮、黑潮 和黑潮逆流、北赤道流和热带水以及黑潮、黑潮逆流和亚热带水等,都有０．０１以上 显著水平相关。黑潮既受制于西太平洋大尺度海洋环流,还受大暖涡变化的影响。 北赤道流递减率反应了亚热带环流西部的辐合状况,它的变化是导致日本以南大 暖涡迁移,黑潮路径变化、停滞的主要原因。     

Interannual variability in the Mindanao Eddy and its impact on thermohaline structure pattern

The major feature,interannual variability and variation cause of the Mindanao Eddy and its impact on the thermohaline structure are analyzed based on the Argo profiling float data,the history observed data and the SODA data.The analysis results show that the Mindanao Eddy is a permanent cyclonic meso-scale eddy and spreads vertically from about 500 m depth upward do about 50 m depth.In addition to its strong seasonal variability,the Mindanao Eddy displays a remarkable interannual variability associated with ENSO.It strengthens and expands eastward during El Nin o while it weakens and retreats westward during La Nin a.The interannual variability in the Mindanao Eddy may be caused by the North Equatorial Counter Current,the North Equatorial Current,the Mindanao Current and the Indonesian Through Flow.The eddy variability can have a great influence on the thermohaline structure pattern in the local upper ocean.When the eddy is strong,the cold and low salinity water inside the eddy moves violently upward from deep layer,the thermocline depth greatly shoals,and the subsurface high salinity water largely decreases,with the upper mixed layer becoming thinner,and vice versa.     

黑潮入侵南海的强弱与太平洋年代际变化及厄尔尼诺-南方涛动现象的关系

在黑潮入侵南海强弱的问题上,到底是太平洋年代际变化(Pacific Decadal Oscillation,PDO)还是厄尔尼诺-南方涛动(El Nio-Southern Oscillation,ENSO)现象在起关键作用,目前还存在着较大争议。本文先以高盐水作为黑潮入侵强弱的示踪物,用120°E断面的高盐水数据和北赤道流分叉点(North Equator Current Bifurcation,NEC-Y)的南北变动进行相关分析,接着,进一步用学者所用的黑潮入侵指数(KI指数,Kuroshio intrusion index和NEC指数,North Equatorial Current index)与北赤道流分叉点南北变动进行相关分析。最后,用EMD(Empirical Mode Decomposition)方法和相关关系分析法分别分析了PDO指数、Nio3.4指数与北赤道流分叉点南北变动的关系并用NECP风场数据探讨其影响机制。结果表明:(1)通过对120°E断面的高盐水的KI指数、NEC指数与NEC-Y的相关分析,表明了北赤道流分叉点的南北变动能够很好地指代黑潮入侵南海的强弱;(2)通过PDO指数和Nio3.4指数与北赤道流分叉点的南北变动的相关性分析,发现PDO指数、Nio3.4指数与北赤道流分叉点的南北变动都具有较好的相关性,都在0.5水平。这些良好的相关性表明了PDO和ENSO对黑潮入侵南海的强弱都具有重要的影响;(3)当处于厄尔尼诺年(拉尼娜)时,赤道太平洋发生西(东)风异常,使得北赤道流分叉点偏北(南),使吕宋岛东侧的黑潮流速减弱(加强),黑潮入侵南海增强(减弱);当PDO处于暖(冷)阶段时,会加强热带太平洋的西(东)风异常,使得黑潮入侵南海增强(减弱)。     

棉兰老涡旋的数值模拟

用一个水平分辨率比较高的非线性正压模式,对热带西太平洋海域里的海流进行了数值模拟。计算海流与观测结果颇相一致。结果表明:赤道以北、棉兰老岛以东附近海域中,棉兰老冷涡在一年的大部分时间里都得到发展,但是其范围、强度和中心位置在各个月份并不相同,显示出很强的季节变化;在哈马黑拉岛东北海域,6月份突然出现了一个反气旋式的涡旋;这个涡旋8月份发展得最强,一直持续到10月份,在11月份就消亡了。     

Near-equatorial eddies off South America

A considerable amount of the Amazon River water that is discharged into the equatorial Atlantic is then advected northward along the shelf by the strong North Brazil Current (NBC). Being relatively fresh, this water remains in the near-surface layer and can serve as an excellent tracer for the complex and variable flow of the offshore mesoscale eddies. Both surface salinity observations and CZCS (Coastal Zone Color Scanner) imagery can be mapped to estimate the circulation patterns of the eddies. Presented here are two sets of XBT (expendable bathythermograph) sections that give the thermal structure of eddies off the Demerara Rise (6–9°N). They were occupied nearly contemporaneously with CZCS imagery obtained during October 1980 and November 1981. Several studies have shown from ship drift data, from CZCS observations, and from Geosat altimetry that, particularly during late summer and fall, the NBC is found to retroflect offshore to the east, supplying the North Equatorial Counter Current (NECC) and is associated with eddies along the coast. Good agreement is shown between the CZCS and a NAVOCEANO AXBT (airborne bathythermograph) survey during this period as well as observations of surface phytoplankton and geopotential anomaly from an earlier 1964 survey. Estimates of volume transport within the eddy structure indicate that at times the offshore retroflection during spring as well as autumn can amount to 10 × 10⁶ m³ s^–1. The pronounced eddy variability off South America is shown by comparing a number of past hydrographic surveys. These suggest that considerable spatial variability can occur as can seasonal changes in volume transport of the NBC and the associated eddy circulation.     

热带西太平洋水位的年际变化与ENSO事件

根据美国ＴＯＧＡ水位中心所提供的１９７５—１９８８年水位月平均资料，分析、讨论了热带西太平洋水位的年际变化特征，特别是与ＥＮＳＯ事件有关的低水位现象。此外，还重点叙述了１９８６—１９８７年ＥＮＳＯ事件中水位沿经向和赤道剖面的变化，以及与此有关的赤道流系的变化。文中还定性地讨论了赤道开尔文波沿赤道剖面的传播特性。     

An extended variable-grid global ocean circulation model and its preliminary results of the equatorial Pacific circulation

1IntroductionThetropicalPacificOceanplaysanimpor-tantroleintheclimatevariabilitiessuchasElNi-no-SouthernOscillation(ENSO)phenomenon(Chao,1993).ManystudieshavefoundthatthetropicalPacificvariabilitiescanhavesignifi-cantinfluenceontheoceancirculationintheseasadjacenttoChina(Yu,1985;Chaoetal.,1996;Wangetal.,2002).TheseaareaadjacenttoChinaischaracterizedbyitscomplextopog-raphyandnumerousnarrowstraits,andthusre-quiresafinegridtoresolve.Tostudytheinter-actionbetweenthetropicalPacificandChinas…     

Why are rings regularly shed in the western equatorial Atlantic but not in the western Pacific?

The western equatorial Atlantic is characterized by the formation and shedding of 3–4 large anticyclonic rings per year. These rings originate from the North Brazil Current which, in response to the vanishing wind stress curl (over the ocean interior), retroflects and turns eastward at around 4°N. After their formation and shedding the rings propagate toward the northwest along the South American coast carrying an annual average of about 4Sv. As such, the rings constitute an important part of the meridional heat flux in the Atlantic.The same cannot be said, however, of the western equatorial Pacific. Here, the situation is entirely different even though the South Equatorial Current retroflects at roughly the same latitude as its Atlantic counterpart, the North Brazil Current. Although the South Equatorial Current retroflection is flanked by two quasi-permanent eddies (the so-called Halmahera and the Mindanao eddies), these eddies are an integral part of the current itself and are not shed. Consequently, they are not associated with any meridional heat flux. An important question is, then, why the two oceans behave in such a fundamentally different way even though the source of the rings, the retroflected currents, are very similar in the two oceans.To answer this question, the two oceans are compared using recently developed analytical and numerical models for the western equatorial oceans. It is first pointed out that, according to recent developments in the modelling of the western equatorial Atlantic, the North Brazil Current retroflection rings are formed, shed and drift to the west because, in the Atlantic, this is the only way by which the momentum flux of the approaching and retroflecting current can be balanced. In this scenario, the northwestward flow force exerted by the approaching and retroflecting North Brazil Current (analogous to the force created by a rocket) is balanced by the southwestward force exerted by the rings as they are formed (analogous in some sense to the kickback associated with a firing gun).On the other hand, in the western equatorial Pacific, the formation and shedding of rings is unnecessary because the southward flowing Mindanao Current provides an alternative mechanism for balancing the northward momentum flux of the South Equatorial Current. This implies that it is the absence of a counter current (such as the Mindanao) in the western Atlantic that causes the formation and shedding of North Brazil Current rings. A remaining difficulty with the above scenario is that most colliding and retroflecting currents (i.e. the Mindanao and South Equatorial currents) are not “balanced” in the sense that they cannot be stationary but rather must drift along the coast. It is shown that, in the case of the western Pacific, the long-shore migration is arrested by the Indonesian Throughflow which allows the “unbalanced” fraction of the approaching currents to leak out into the Indian Ocean. This resolves the above difficulty and allows the retroflection to be approximately steady.     

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。