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。     

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...     

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。     

赤道潜流变化及其与ENSO的关系

应用TOGA/TAO实测海流和SODA全球海洋再分析资料,分析研究了热带太平洋赤道潜流的变化特征及其与ENSO循环的关系,初步探讨了赤道潜流变化对两种不同类型(中部型和东部型)ENSO事件的影响。对赤道潜流距平场的EOF分解表明,第一模态为"东太平洋潜流模态",特征向量主要反映东太平洋赤道潜流的变化情况;第二模态为"中太平洋潜流模态",特征向量主要反映中太平洋赤道潜流的变化情况;这两个主要模态基本可以反映赤道潜流距平场的主要信息。这两个模态对应的时间系数有明显的年际变化特征,并且与NINO指数都有较好的负相关,最大相关均通过99.9%的信度检验。相关分析表明潜流第一模态的变化滞后于NINO指数变化,而第二模态的变化则提前于NINO指数变化,即ENSO事件对东太平洋赤道潜流的变化有一定影响,而中太平洋的潜流变化又会对ENSO事件产生影响。通过个例分析表明,中太平洋赤道潜流的变化对两种不同类型ENSO事件的发生有重要影响。在东部型ENSO事件发生前,中太平洋赤道潜流增强,这样西太平洋暖池的异常海温在潜流的引导下快速向东传播,直接到达东太平洋形成东部型ENSO事件;中部型ENSO事件发生前,中太平洋赤道潜流明显减弱,西太平洋的异常海温不能迅速东传速,在中太平洋堆积上升到达海面,使得中部型ENSO事件爆发。     

赤道潜流的奥秘

1951年,美国海洋学家克伦威尔和他的同事,在太平洋的赤道海域进行了鲔鱼生活习性及环境条件的考察研究。其考察的方法比较简单,就是把玻璃浮子串     

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。     

两次非典型厄尔尼诺期间热带太平洋主流系和赤道行星波研究

两次非典型厄尔尼诺事件发生期间,Walker环流中的西太平洋部分显着减弱,Hadley环流中的东太平洋部分显着增强.西太平洋距平西风应力增强向东伸展;东太平洋距平北风应力增强向南伸展.西太平洋暖池的能量可以两种方式向东传播:赤道Kelvin波温跃层模态和流速模态.温跃层模态向东输送的总能量大于流速模态向东输送的总能量.1982～1983年厄尔尼诺事件中,赤道Kelvin波温跃层模态起主要作用,赤道潜流减弱;1986～1987年厄尔尼诺事件中,赤道Kelvin波流速模态起主要作用,赤道潜流增强.厄尔尼诺事件期间,赤道潜流消失、反向现象是一种局地性海洋响应,这种现象不伴随赤道Kelvin波向东传播.     

El Ni■o期间太平洋赤道潜流逆转事件

联系1982～1983年El Nino事件期间的太平洋赤道潜流逆转事件,研究了1976～1977年和1986～1987年两个El Nino年中137°E和165°E断面上出现的相同现象。认为赤道潜流运动逆转并非1982～1983年El Nino期间的偶发事件。西太平洋赤道海域是监测赤道潜流变异及其与El Nino事件关系的关键地区。     

赤道东太平洋海温与黄海气旋

本文统计分析了黄海气旋与赤道东太平洋海温的关系。结果得出，赤道东太平洋海温的暖冷，不仅与黄海气旋的多少有较好的对应关系，并且与黄海气旋的强弱也有较为密切的联系。赤道东太平洋海温对黄海气旋的影响，是由于海温异常引起副高及其北侧高度场的差异进而影响黄海气旋的。     

西北太平洋副热带逆流、北赤道流、北赤道逆流几个特征的比较

根据137°E断面1967～1995年冬、夏季的温、盐资料,计算和分析该断面的地转流;分析144°E断面上投放卫星跟踪漂流浮标的漂移轨迹;结合CSK图集中的海面重力势分布,对副热带逆流、北赤道流和北赤道逆流几个特征的相同点和不同点进行比较,得出若干有益的结论:(1)副热带逆流、北赤道流、北赤道逆流,并不是单纯的单支海流,而是存在着两支或多支现象;(2)流速结构的带状分布,东、西向流相互交错间隔出现,流层较浅,均为表层流或近表层流;(3)多年平均而言,3支海流的流速以北赤道逆流最强,北赤道流次之,副热带逆流最弱;流量则不同,北赤道流最大,副热带逆流最小,北赤道逆流居中.3支海流的流速夏季均大于冬季,但流量稍有差异:副热带逆流和北赤道流均具有夏强、冬弱的特点,而北赤道逆流为冬强、夏弱;(4)冬季,副热带逆流的"源地",位于巴士海峡和台湾以东"副热带脊"的一个"暖脊"中心附近海域;(5)冬季,卫星跟踪漂流浮标的漂移轨迹,基本上反映出北赤道流和北赤道逆流的路径.但因副热带逆流区为涡旋频繁区,致使浮标漂移轨迹难以反映出副热带逆流的路径.     

Trace metals in the Western Pacific: temporal and spatial variability in the concentrations of Cd, Cu, Mn and Ni

Profiles of total dissolvable Cd, Cu, Mn and Ni are reported for samples collected from the southwest Pacific in 1989, from the western equatorial Pacific along 155°E at 5°S, 0° and 5°N in 1990 and 1993, and along the equator from 143°E to 152°E and in the Bismarck Sea in 1997 and 2000. Profiles of Cd along 155°E in 1990 and along the equator were essentially the same but, in 1993, Cd values at 5°N were higher by a factor of about 1.5–2 than at 5°S over the depth range 500–1500 m. Similar, but less pronounced, differences were observed for PO₄ and Ni. Cd and Ni were both strongly correlated with PO₄, and an even stronger correlation was found between Ni and Cd. The concentration of Ni did not fall below ≈2 nmolkg⁻¹, even in the nitrate-depleted waters of the western equatorial Pacific, where primary production is strongly dependent on recycled nitrogen (mainly ammonia and urea). It is proposed that this residual Ni is not bioavailable and that Ni could be biolimiting, since the metabolism of urea requires the nickel-containing enzyme urease. The impact of the Sepik River on Cd, Cu and Ni concentrations was small but elevated concentrations of Mn were observed near the Sepik River and close to the coast suggesting that the rivers and sediments on the north coast of New Guinea are a significant local source of Mn to the Bismarck Sea. Simple mass balance calculations show that the elevated levels of Mn observed in the Equatorial Undercurrent cannot be due to input from the rivers of New Guinea and they were attributed to the trapping of particulate matter due to strong current shear. A strong hydrothermal source of Mn was observed in the central Bismarck Sea.     

Research on the Propagation Acting of the Equatorial Planetary Waves on the Western Equatorial Pacific Warm Pool Heat

1 IntroductionIn the Equatorial Pacific, due to the difference between the atmospheric circulation and air-sea interaction, the near-surface seawater heat structure in the eastern and western Pacific presents two ℃obviously different characteristics: warm pool ( > 28 ) in the western equatorial Pacific and cold ℃tongue ( < 24 ) in the eastern equatorial Pacific. The water bodies of these two heat structures would give rise to change in spatial distribution under the action of the equato…     

赤道行星波对西赤道太平洋暖池热传播的作用

利用热带海洋和全球大气试验(TOGA)期间(1980～1996年)热带大气海洋观测阵(TAO)的长期浮标资料,分析了赤道行星波对西赤道太平洋暖池热传播的作用。结果表明,西赤道太平洋暖池纬向热传播主要出现在次表层水体中,并沿温跃层向东传播;而向西传播的季节热结构变化主要出现在中、西赤道太平洋的混合层中;驻波型传播在西赤道太平洋主要出现于温跃层,在中赤道太平洋主要出现于混合层和温跃层,在东赤道太平洋主要出现于混合层。在平均条件下,赤道太平洋上层水温纬向热传播信号以驻波型和东传型较强,西传型较弱。赤道Kelvin波压力分量贯穿西、东赤道太平洋并向东输送暖池热能,纬向流分量的热输送主要出现在西赤道太平洋;Rossby波压力分量的热输送主要出现在东、中赤道太平洋;混合Rossby重力波激发纬向流的热输送作用比相应温跃层扰动强。在平均条件下,赤道太平洋上层水温的驻波型变化制约了西赤道太平洋暖池热量的持续向东输送,因此形成了赤道太平洋水温的正常季节变化形态。当水温的驻波型变化减弱而东传型变化加强时,随后将形成厄尔尼诺现象。     

Biogeochemical impact of a model western iron source in the Pacific Equatorial Undercurrent

Trace element distributions in the source waters of the Pacific Equatorial Undercurrent (EUC) show the existence of elevated total acid-soluble iron concentrations. This region has been suggested to contribute enough bioavailable iron to regulate interannual and interglacial variability in biological productivity downstream in the high-nitrate low-chlorophyll upwelling zone of the eastern equatorial Pacific. We investigated the advection and first-order biogeochemical impact of an imposed, data-based iron maximum in the western Pacific EUC using an ecosystem model forced by a global dynamical model. We imposed two source profiles of iron constrained by total acid-soluble iron measurements. Though the data for total acid-soluble iron included both dissolved and acid-soluble particulate iron species, we treated all of the total acid-soluble iron as if it was dissolved and bioavailable. A deeper (270 m) source was centered in the density horizon of the observed iron maximum and a shallower (180 m) source was located in the core of our model's EUC, where a dissolved iron maximum has been frequently postulated. These source runs were compared with a control run that contained no specific source of iron associated with the EUC. In the source runs elevated iron concentrations were simulated in the EUC across its entire zonal span, evident as a subsurface plume of dissolved iron slightly below the core of the EUC. In the control run there was no iron maximum associated with the EUC. Upwelling of iron-replete water in the central and eastern equatorial Pacific increased integrated primary productivity in the Wyrtki box (180°W:90°W, 5°S:5°N, 0:200 m) by 41% and 66% for the deeper and shallower iron perturbation, respectively. The source runs increased the realism of the zonal extent of HNLC conditions and the meridional distributions of biological productivity, relative to the control run. However, in the source simulations surface chlorophyll concentrations were too high by a factor of two and maximum surface nitrate concentrations were too low, relative to climatologies. The relative abundance of diatoms roughly doubled upon the input of additional iron, exceeding field observations. Though biogeochemical data are limited and we did not adjust parameters to optimize the model fits to observations, these results suggest that acid-soluble particulate iron supplied to the EUC in the western equatorial Pacific is unlikely to be entirely bioavailable.     

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.     

棉兰老流和棉兰老潜流在季节尺度上的关系研究

The ocean general circulation model for the earth simulator(OFES) products is applied to estimate the transports of the Mindanao Current(MC) and the Mindanao undercurrent(MUC) and explore the relation between them on seasonal scale. In general, the MUC is composed of the lower part of the Southern Pacific Tropical Water(SPTW)and Antarctic Intermediate Water(AAIW). While the deep northward core below 1 500 m is regarded as a portion of MUC. Both salinity and potential density restrictions become more reasonable to estimate the transports of MC/MUC as the properties of water mass having been taken into consideration. The climatological annual mean transport of MC is(37.4±5.81)×10~6 m~3/s while that of MUC is(23.92±6.47)×10~6 m~3/s integrated between 26.5 σ_θ and 27.7 σ_θ, and(17.53±5.45)×10~6 m~3/s integrated between 26.5 σ_θ and 27.5 σ_θ in the OFES. The variations of MC and MUC have good positive correlation with each other on the seasonal scale: The MC is stronger in spring and weaker in fall, which corresponds well with the MUC, and the correlation coefficient of them is 0.67 in the OFES.The same variations are also appeared in hybrid coordinate ocean model(HYCOM) results. Two sensitive experiments based on HYCOM are conducted to explore the relation between MC and MUC. The MUC(26.5σ_θ27.7) is strengthening as the MC increases with the enhancement of zonal wind field. It is shown,however, that the main part of the increasement is the deeper northward high potential density water(HPDW),while the AAIW almost remains stable, SPTW decreases, and vice versa.     

Study on the characteristics of the marine boundary layer in the Equatorial Pacific

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太平洋北赤道流表层流速及分叉点位置

确定太平洋北赤道流表层流速及分叉点位置的变化是海洋环境研究中的1个重要问题。使用1987～1998年的WOCE浮标资料,通过估算得到了季节平均和年平均意义下北赤道流表层流速(1989～1998)。计算结果显示:北赤道流表层流的流速冬季最大,夏季最小,春秋两季相仿。在厄尔尼诺发生年的第2年,夏季平均流速往往较大。对浮标轨迹的逐年分析表明表层北赤道流分叉点的位置在11°N～14 .7°N之间,从轨迹较为密集的4年的分析可以看出,表层流分叉点的位置具有年际变化,其中,2个ElNino年分叉点偏北。     

降低水平压力梯度误差的方法比较

由于坐标变换的关系,σ坐标海洋模式在处理陡峭地形时会产生较大的水平压力梯度误差.为减少水平压力梯度误差,前人提出了一系列改进的方法,这些方法可分为减去平均密度法、平滑地形法、网格变换法和水平压力梯度计算方程变换法4类.水平压力梯度计算方程变换法又可分为密度雅克比法、高阶精度法、有限体积法和转换到z坐标下计算水平压力梯度法.利用POM模式模拟理想海山来比较标准密度雅克比法、线性插值到z坐标法、四阶精度插值法、三次方多项式拟合法和权重密度雅克比法在计算水平压力梯度中出现的误差.模式初始时垂向分成,水平均匀,外模时间步长为12 s,内模时间步长为360 s,计算时间为360 d.从最大流速误差的结果可以看出,标准密度雅克比法得到的最大流速误差为0.45 m/s左右;线性插值到z坐标法得到的最大流速误差达到0.7 m/s;四阶精度方法计算得到的最大流速误差为0.3 m/s;权重密度雅克比方法和三次方多项式拟合法计算得到的最大流速误差相差不大,都只有0.2 m/s左右.标准密度雅克比法计算得到的单位质量平均动能最大,为9×10-4 m2/s2;四阶精度方法和线性插值到z坐标方法计算得到的单位质量平均动能差不多,为3×10-4 m2/s2;三次方多项式拟合法计算得到的单位质量平均动能为1.9×10-4 m2/s2;权重密度雅克比方法计算得到的单位质量平均动能最小,仅为1×10-4 m2/s2.标准密度雅克比法的计算耗时最短,为294 min;与其相比,三次方多项式拟合法的计算耗时增加了5.9%;权重密度雅克比法的计算耗时增加了8.8%;四阶精度插值法的计算耗时增加了23.6%.线性插值到z坐标法的计算耗时最长,需要384.5 min,相对于标准密度雅克比法的计算耗时增加了30.6%.因此,综合最大流速误差、平均动能和计算耗时的结果可知,线性插值到z坐标法的计算结果相对较差,采用权重密度雅克比法能较好地降低水平压力梯度误差.