风生沿岸上升流及沿岸流的一个非稳态模式

七十年代以来,有关沿岸上升流及沿岸流的研究受到了人们异乎寻常的重视。除其本身的理论意义之外,这主要还是因为世界上的鱼有一半是在面积仅占世界海洋总面积千分之一的沿岸上升流区捕获的缘故(Ryther,1969)。由于广泛的海上调查,世界上新发现的上升流区愈来愈多。上升流已不再是东部边界流独具的特征了,在西部边界也发现了不少上升流区。     

东海北部一个夏季气旋型涡旋的初步分析

近十年来,随着海洋探测技术的发展,在世界各大洋里都发现了中尺度涡旋,这是物理海洋学上的重大进展之一。目前所发现的中尺度涡旋,不管是在大洋里,还是在极地区,一般均处于千米以上的深水区。但在陆架浅海区，海底摩擦要消耗大量的能量,是否也会出现这类涡旋,这是一个令人感兴趣的问题。 根据现有文献和我们对近几年东海水文调查资料的初步分析得知,在我国陆架区至少有两个气旋型涡旋,一个在台湾东北的彭佳屿附近海域,另一个在济州岛西南海域。对前者,管秉贤(1978)和M.Uda(1974)等均从冷水团的角度进行过研究,特别是日本学者在此海域进行了多次调査。至于后者,井上尚文(1975)曾根据1969年11月投放的“人工水母”(即底层流示踪器)的资料分析指出:“在黄海暖流和黄海沿岸流两股底层流的中间区域,有黄海冷水伸入。在秋、冬期间,南北流向呈反时针方向旋转。从而可以认为,以调查海区的中部(济州岛南面)海底为中心,有一个范围相当大的环流存在。”由此人们自然会提出这样一个问题:在春、夏两季,这一反时针方向的水平环流是否继续存在。尤其在夏季,自南北上进入黄海和东海的黑潮及其分支(对马暖流和黄海暖流)与黄海、东海沿岸流系交错汇合,盘踞在下层的冷水又极度发展,使得环流结构和水文状况较冬季复杂得多,这时的情况又将变得怎样?本文主要根据1972年7-8月常规水文观测资料,同时参照近几年的水文资料,对此问题作一初步探讨。 本文研究的重点海区的范围是30°30′-33°00′N,124°00′-127°E,如图1阴影部分所示。为了便于资料的分析,在绘制温、盐度等平面分布图时,将其范扩大到28°-34°N之间的大部分海域。 本文引用的资料主要来源于国家海洋局标准断面调查资料,东海渔业资源调査资料，日本气象厅海洋气象观测资料和南朝鲜水产振兴院海洋观测资料。     

关于浙江沿岸上升流的成因及动力结构的研究

上升流即海洋中持续垂直向上的海水运动,这种运动在海洋中是比较普遍的,但是，就其大小而言,却有着巨大的差异——可达几个数量级。所以,只有在那些量值较大的区域才引起人们的注意;而在量值较小的区域由于表象不够显著——对各种特征场特别是温度场的影响不太明显,往往被人们所忽视。 尽管上升流的流速与水平流速相比甚小,一般在10-5-10-2厘米/秒范围内(大约相当于每天1厘米至10米),但其作用却是巨大的。首先,就整个海洋来说,它是海洋环流不可分割的一个组成部分,是上层水与下层水沟通交换的渠道。其次，上升流在生产实践中具有十分重要的意义,它对渔业生产有着巨大的影响,它能将富含营养盐的中、下层水带到强光合作用层,为浮游植物提供充分的养料,从而促进鱼类佴料的繁殖。海洋中出现上升流的区域仅占世界整个海洋面积的1‰左右,但上升流区的渔获量却占全世界总产量的50%左右；我国浙江近海、海南岛东南水域以及汕头外海诸上升流区同时均为良好渔场。因此,沿岸上升流越来越引起人们的重视。 从现有文献来看,我国近海。在渤海、黄海、东海和南海四个海区都有上升流存在,如渤海中部、黄海冷水团区、浙江近海、汕头外海以及海南岛东南沿海等。但是,关于这一现象,除少数海洋工作者曾提及过外,至今还缺乏专门的研究。 本文旨在利用现有的海流、水温、盐度和气象资料,就浙江沿岸(见图1)上升流产生的动力来源及环流模式进行初步的分析研究,提出粗路估算上升流的方法、指标,并提出尚待进一步解决的几个问题。所用资料主要是1958-1960年全国海洋普查、1963-1966年标准断面以及我所六十年代以来(到1973年)观测的有关资料。此外,还用了国家海洋局和浙江省气象局所提供的部分海流资料及沿岸合站的水文气象资料。     

东海北部的一个气旋型涡旋

东海北部是几个流系交汇的地方，东有黄海暖流向西北流人黄海，西有所谓黄海沿岸流南下，南有黑潮北上余脉；另外，在夏季，上层还有长江冲淡水的影响(见图1)。因此，这里的水文状况相当复杂，曾引起了不少中外学者的注意。井上尚文根据1969年11月在该海区投放的海底漂流器资料分析的结果表明，济州岛西南海域的底层流，在秋、冬两季为一范围相当大的反时针水平环流。胡敦欣等进一步指出，夏季在大约以31°30’N，125°30''E为中心，尺度为100-200km 的范围内存在着一个气旋型涡旋；阐明了这一涡旋形成的动力原因(黄海暖流、黄海沿岸流和黑潮北上余脉之间的相互作用)和热力学因子(黄海冷水的南伸)；对这一海区海底圆形软泥沉积的形成机制作了简要的说明，并依此推测这一涡旋的常年存在。近几年来，我们又作过多次专题性调查，取得了较好的资料。本文旨在进一步论证这一涡旋的常年存在，阐明其多年变化，探讨引起这种变化的原因，并讨论几个有关的问题。     

相空间反演方法及其在海洋资料分析中的应用

时间序列重建相空间理论是研究实验数据所隐含着非线性复杂现象(如奇怪吸引子、分形、自相似结构及混沌)的有力工具.本文在时间序列重建相空间理论基础上,建立了在嵌入相空间中反演动力系统方法,并将此方法应用于TOGA COARE提供的海表温度(SST)时间序列资料分析中,给出了奇怪吸引子关联维数、嵌入相空间维数、Lyapunov特征指数、Kolmogorov熵及可预报时间尺度.利用相空间中反演动力系统,在可预报时间尺度上进行预报实验,其结果与实测值基本一致.     

Study of long-wave breaking

This paper reports study on the mechanism of long-wave breaking in a one-dimensional open chan-nel,without bottom friction,or with linear bottom friction.In general,the wave breaking phenomenon is related to the notion of"blow-up of solution"and can be studied by using the blow-up theory of par-tial differential equations(PDE).A pair of Riemann invariants are introduced to transform the governingequations into ordinary differential equations(ODE)along the characteristic directions of the governingequations.From the properties of the solutions of the ODE,the time and location of wave breakingare estimated and the criterion of long-wave breaking for the case with linear bottom friction is obtained.     

A time-dependent baroclinic model on NEC bifurcation

As it is well-known, the North Equatorial Current (NEC) bifurcates into the Kuroshio flowing northward and the equatorward Mindanao Current, which is well depicted by Munk’s theory in 1950 in terms of its climatology. However, Munk’s theory is unable to tell the NEC bifurcation variability with time. In the present paper, a time-dependent baroclinic model forced by wind, in which temporal and baroclinic terms are added to Munk’s equation, is proposed to examine the seasonal variability of the NEC bifurcation latitude. An analytical solution is obtained, with which the seasonal variability can be well described: NEC bifurcation reaches its northernmost position in December and its southernmost position in June with a range of about 1° in latitude, consistent with previous results with observations. The present solution will degenerate to Munk’s one in the case of steady and barotropic state.     

Effect of low-frequency Rossby wave on thermal structure of the upper southwestern tropical Indian Ocean

We investigate the influence of low-frequency Rossby waves on the thermal structure of the upper southwestern tropical Indian Ocean (SWTIO) using Argo profiles, satellite altimetric data, sea surface temperature, wind field data and the theory of linear vertical normal mode decomposition. Our results show that the SWTIO is generally dominated by the first baroclinic mode motion. As strong downwelling Rossby waves reach the SWTIO, the contribution of the second baroclinic mode motion in this region can be increased mainly because of the reduction in the vertical stratification of the upper layer above thermocline, and the enhancement in the vertical stratification of the lower layer under thermocline also contributes to it. The vertical displacement of each isothermal is enlarged and the thermal structure of the upper level is modulated, which is indicative of strong vertical mixing. However, the cold Rossby waves increase the vertical stratification of the upper level, restricting the variability related to the second baroclinic mode. On the other hand, during decaying phase of warm Rossby waves, Ekman upwelling and advection processes associated with the surface cyclonic wind circulation can restrain the downwelling processes, carrying the relatively colder water to the near-surface, which results in an out-of-phase phenomenon between sea surface temperature anomaly (SSTA) and sea surface height anomaly (SSHA) in the SWTIO.     

137°经向断面温、盐度的年际变异

系统地分析了１３７°Ｅ断面温、盐度的多年变化,主要结果为：（１）１３７°Ｅ断面１００ｍ层温度,在低纬度海域于某些年份出现异常低温,此现象可能与厄尔尼诺事件有关;指出棉兰老冷涡的存在是造成该断面于６°～８°Ｎ附近出现低温的主要原因．（２）厄尔尼诺期间,冬季１３７°Ｅ断面上２８℃等温线所在纬度小于其多年平均值．（３）冬季１３７°Ｅ断面上次表层高盐水可划分为强型、次强型、中等型和弱型４种类型．     

Seasonal and intraseasonal variations of the surface Taiwan Warm Current

To study seasonal and intraseasonal variations of the Taiwan Warm Current (TWC) in detail Rotated Empirical Orthogonal Function (REOF) and Extended Associate Pattern Analysis (EAPA) are jointly adopted with daily sea surface salinity (SSS), sea surface temperature (SST) and sea surface height (SSH) datasets covering 1126 days from American Navy Experimental Real-Time East Asian Seas Ocean Nowcast System in the present paper. Results show that the first and second REOFs of SST in the southern East China Sea (SECS) account for 50.8% and 39.8% of the total variance. The surface TWC contains persistent (multi-year mean), seasonal and intraseasonal components. The persistent one mainly inosculates with the Kuroshio but the seasonal and intraseasonal ones are usually active only on the continental shelf. Its persistent component is produced by inertial flow of the Kuroshio, however its seasonal and intraseasonal ones seems coming from seasonal and intraseasonal oscillations of monsoon force. The seasonal one reaches its maximum in late summer,lasting about four months and the intraseasonal one takes place at any seasons, lasting more than 40 days.