南太平洋南极中层水的中尺度特征

The Argo float observations are used to investigate the mesoscale characteristics of the Antarctic Intermediate Water(AAIW) in the South Pacific in this paper. It is shown that a subsurface mesoscale phenomenon is probably touched by an Argo float during the float's ascent-descent cycles and is identified by the horizontal salinity gradient between the vertical temperature-salinity profiles. This shows that the transportation of the AAIW may be accompanied with the rich mesoscale characteristics. To derive the spatial length, time, and propagation characteristics of the mesoscale variability of the AAIW, the gridded temperature-salinity dataset ENACT/ENSEMBLE Version 3 constructed on the in-situ observations in the South Pacific since 2005 is used. The Empirical Mode Decomposition method is applied to decompose the isopycnal-averaged salinity anomaly from26.8 σθ–27.4 σθ, where the AAIW mainly resides, into the basin scale and two mesoscale modes. It is found that the first mesoscale mode with the length scale on the order of 1 000 km explains nearly 50% variability of the mesoscale characteristics of the AAIW. Its westward-propagation speeds are slower in the mid-latitude(around 1cm/s) and faster in the low latitude(around 6 cm/s), but with an increasing in the latitude band on 25°–30°S. The second mesoscale mode is of the length scale on the order of 500 km, explaining about 30% variability of the mesoscale characteristics of the AAIW. Its westward-propagation speed keeps nearly unchanged(around 0.5cm/s). These results presented the stronger turbulent motion of the subsurface ocean on the spatial scale, and also described the significant role of Argo program for the better understanding of the deep ocean.     

LABORATORY MEASUREMENTS OF THE EFFECTS OF VISCOSITY ON SHORT WATER WAVE SPECTRA AND IMPLICATION FOR RADAR REMOTE SENSING OF THE OCEAN SURFACE

Using an X-band radar and a mechanical short wave generator, we measured the dependenceof radar return power on the viscosity of water which was adjusted by changing the watertemperature. From the measurements we drew two inferences: (1) the spectral density of short waterwaves, F, depends strongly on the viscosity of waterF(v)=F_0~mwhere is normalized viscosity, and m=-1.72; and (2) the normalized radar cross section, σ_0(dB), dependsstrongly on the water temperature△σ_0 (dB)=O.217△TAnalyses indicate that these dependencies can be observed in the field only at low wind conditionsat which the Bragg scattering is a dominant mechanism for producing the radar return signals. Theresults of this study can be used to interpret the sharp variability in radar cross section across a watertemperature front and SAR images of oeeanic phenomena.     

DETERMINATION OF GEOSTROPHIC FLOW BY APPLYING THE PRINCIPLE OF MINIMUM ENERGY AND THE INVERSE METHOD

This article gives a computing method to calculate the geostrophic current. The fact that kinetic energy of geostrophic motion and geostrophic potential energy reach minimum simultaneously, Fomin's "principle of minimum kinetic energy" is equivalent to the principle of minimum geostrophic potential energy . We concluded that horizontal geostrophic velocities at different depths are along the same direction . Combining our method with C. Wunsch's inverse method we can obtain the velocity components along and normal to the hydrographic sections . We used and analysed CTD and current meter data of " Experiment No . 3 " exploration, December 1985-January 1986, in the west Pacific Ocean - Philippine area.     

Analysis of bathymetric features using sar image: An example from the southern North Sea

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用Geosat高度计数据提取东海大地水准面

大地水准面是地球重力势等势面,它反映了地球形状及海面重力场异常特征,对大地测量学及海底探矿意义重大.本文利用Geosat高度计50个ERM周期共2.3a的数据,对包括东海区域的20°～40°N,120°～140°E海域进行了大地水准面反演计算.本文采用时间平均处理法有效地抑制了高度计数据中含有的由海洋时变因素引起的高度偏差,并用两种计算模型得到了东海大地水准面.计算出的大地水准面可反映出某些小区域海底特征,但与大尺度海底地形相关较差,这主要是由地壳均衡补偿作用引起的.对计算误差分析得出,采用模型-1和模型-2得出的大地水准面中残留的轨道误差分别为10.8和5.6cm,与OSU91A大地水准面模型偏差分别为37.6和42.2cm,时间平均处理使海洋时变因素引起的海面高度偏差降低了7倍.     

海浪混合参数化的渤海、黄海、东海水动力环境数值模拟

在浪-流耦合的概念下,对Princeton Ocean Model(POM)模式进行改进,增加特征波参数下的海浪混合作用,并把潮流和环流同时模拟,得到了渤海、黄海、东海典型的环流和水文特征,特别是夏季黄海的温跃层现象,夏季长江冲淡水扩展路径以及我国东部海域冬季和夏季典型环流等.研究表明,海浪的作用使海洋上层混合得更均匀,潮流的作用使海洋底层混合得更均匀,二者是温跃层形成的重要原因;考虑潮效应模拟流场,由于潮扩散和潮余流的作用,长江冲淡水路径与实际观测更为符合.     

海冰物理特征值及其对桩柱作用力的测量

1970—1974年,我们在渤海湾进行了浮冰对固定平台桩柱作用力、浮冰漂移及海冰某些物理特征值的测量工作。本文着重介绍各项观测所使用的方法和仪器。关于观测资料的分析结果,将另文报道。一、浮冰对固定平台桩柱作用力的测量用电阻应变法测量浮冰对桩柱的作用力,其测量系统方框图如下。     

黄海冷水团热结构及其环流解析研究

本文从一般的流体动力学－热力学方程组出发，通过对历史资料的分析，确立了描述黄海冷水团热结构及其环流的非线性控制方程组，得出近似解析解。理论计算结果表明，夏季北黄海冷水团区域存在中心上升边缘下降的气旋式密度环流。     

表面粗糙度对海浪成长率的影响

本文在Ｍｉｌｅｓ准层流风生波模型基础上，引入表面粗糙度沿波面不均匀分布的线性模型，通过不稳定性分析，导出了平均压力随表面粗糙度变化和海浪成长率之间的关系，表明表面粗糙度的不均匀分布是影响海浪成长率的一个重要因素。     

海洋内波的控制方程组

从海水质量守恒律、盐量守恒律、动量守恒律、熵变化律和海水状态律出发，给出了低频变密度海洋运动的原始控制方程和它的各类实用形式。在推导的过程中着重明确控制方程各种近似形式的数学物理意义，这使我们在使用这些方程时更严格、更准确。