Surface current field and seasonal variability in the Kuroshio and adjacent regions derived from satellite-tracked drifter data

The muhiyear averaged surface current field and seasonal variability in the Kuroshio and adjacent regions are studied. The data used are trajectories and （1/4） ° latitude by （1/4） ° longitude mean currents derived from 323 Argos drifters deployed by Chinese institutions and world ocean circulation experiment from 1979 to 2003. The results show that the Kuroshio surface path adapts well to the western boundary topography and exhibits six great turnings. The branching occurs frequently near anticyclonic turnings rather than near cyclonic ones. In the Luzon Strait, the surface water intrusion into the South China Sea occurs only in fall and winter. The Kuroshio surface path east of Taiwan, China appears nearly as straight lines in summer, fall, and winter, when anticyclonic eddies coexist on its right side; while the path may cyclonically turning in spring when no eddy exists. The Kuroshio intrusion northeast of Taiwan often occurs in fall and winter, but not in summer. The running direction, width and velocity of the middle segment of the Kuroshio surface currents in the East China Sea vary seasonally. The northward intrusion of the Kuroshio surface water southwest of Kyushu occurs in spring and fall, but not in summer. The northmost position of the Kuroshio surface path southwest of Kyushu occurs in fall, but never goes beyond 31 °N. The northward surface current east of the Ryukyu Islands exists only along Okinawa-Amami Islands from spring to fall. In particular, it appears as an arm of an anti- cyclonic eddy in fall.     

A dataset of global ocean surface currents for 1999-2007 derived from Argo float trajectories: Comparison with surface drifter and TAO measurements

A dataset of surface current vectors with error estimate from 1999 to 2007 is derived from the trajectories of the Array for Real-time Geostrophic Oceanography （Argo） drifting on surface over the global ocean. The error of the estimated surface currents is about 4.7 cm s-1 which is equivalent to the accuracy of the currents determined from the surface drifters. Geographically, the Argo-derived surface currents can fill many gaps left by the Global Drifter Program due to the greater number of floats, and can provide a complementary in situ observational system for monitoring global ocean surface currents. The surface currents from the Argo floats are compared with the surface drifter-derived currents and the Tropical Atmosphere Ocean program （TAO） measurements. The comparisons show good agreement for both the current amplitude and the direction of surface currents. Results indicate the feasibility of obtaining ocean surface currents from the Argo array and of combining the surface currents from Argo and the ocean surface drifters for in situ mapping of the global surface currents. The authors also make the dataset available to users of interest for many types of applications.     

Argos漂流浮标的若干观测结果

表层漂流浮标是一种利用Argos卫星系统定位与传送数据的海洋观测设备,它可以利用Lagrangian法则连续观测表层海流及表层水温。文章利用近年在南海和西太平洋投放的部分卫星跟踪表层漂流浮标所取得的观测资料,分析观测海域的表层海流特征及其漂移路径上的温度变化,得出以下结果。(1)由浮标的漂移轨迹看出,黑潮表层流路年际变异相当大。(2)2003年1月,黑潮表层水有入侵南海的趋势,似无西北太平洋表层水深入南海的迹象;夏季南海表层水由南海流出经吕宋海峡汇入黑潮主干。(3)秋季台湾东北海区存在一个强反气旋涡,空间尺度约270km。(4)黑潮主干在秋末冬初经过东海时明显呈弯曲流动,并形成许多小尺度的气旋式涡。(5)在九州西南海域,黑潮表层流并无分支北上进入对马暖流区。(6)2003年春季,黑潮在日本以南的弯曲不明显,并伴随有冷、暖涡产生,暖涡的强度和空间尺度都要比冷涡大得多。(7)由漂流浮标观测得到的的表层海水的温度分布明显呈日变化和季节变化的特征。在浮标漂移路径呈反气旋或气旋式转动的区域,表层水温对应出现高或低温区;但出现在台湾以东的低温区则与此时期的台风过境有关。     

Dynamical features of near-inertial motions in global ocean based on the GDP dataset from 2000 to 2019

Based on the latest oceanic surface drifter dataset from the global drifter program during 2000–2019, this study investigated the global variation of relative frequency shift(RFS), near-inertial energy(NIE) and inverse excess bandwidth(IEB) of near-inertial motions, and analyzed their relations with oceanic mesoscale dynamics, relative vorticity and strain. Compared with previous works, we have some new findings in this study:(1) the RFS was high with negative values in some regions in which we found a significant blue shift of the RFS in the equatorward of 30°N(S) and from 50°N to 60°N in the Pacific, and a red shift in the western boundary currents and their extension regions, the North Atlantic and the Antarctic Circumpolar Current regions;(2) more peak values of the NIE were found in global regions like the South Indian Ocean, the Luzon Strait and some areas of the South Ocean;(3) the global distribution of the IEB were characterized by clear zonal bands and affected by vorticity and wind field;(4)the RFS was elevated as the absolute value of the gradient of vorticity increased, the IEB did not depend on the gradient of vorticity, and the eddy kinetic energy(EKE) weakened with the decrease of the absolute value of RFS;(5) the NIE decreased with increasing absolute value of the relative vorticity and the gradient of vorticity, but it increased with increasing strain and EKE when EKE was larger than 0.003 2 m~2/s~2.     

基于卫星漂流浮标轨迹的东海边界交换估算方法研究

东海陆架斜坡和台湾海峡是我国东部近海从大洋和南海获取热量、盐量和营养盐的两个主要边界。本文建立了一个不规则分布漂流浮标轨迹的网格化处理方法和跨边界交换估算方法。该方法得到的漂流浮标轨迹累计次数再现了黑潮主轴位置并表明主轴两侧浮标存在显著的跨陆坡交换现象。浮标轨迹的统计结果揭示了东海陆坡上水体交换具有显著的区域性,即陆坡上存在7个主要交换区,3个交换区以入流为主,另4个交换区以出流为主。研究也表明跨东海陆坡交换具有明显的季节变化特征,秋季交换最剧烈且入流最显著,春季最弱。穿越台湾海峡的交换主要以北向入流为主,海峡东侧的交换更加明显,一年之中夏季最显著,春、冬季最弱。     

黑潮水入侵东海陆架及陆架环流的若干现象

利用WOCE-SVP和中国近海环流观察项目的卫星跟踪表层测流浮标资料，详细分析了黑潮及其入侵东海陆架和东海陆架上层环流的分布状况，结果表明：黑潮从台湾东部进入东海后，明显入侵陆架，并在复杂地形的作用下使其流路呈现多种变化，分析结果还显示，对马暖流不仅仅是黑潮的延续，而是多支流合成的结果，通过资料分析发现：秋节东海黑潮西侧100m等深线处可能存在一支与黑潮反向的逆流，关于它存在的季节变化和动力机制有待进一步的深入研究。     

南极绕极流的表层环流结构和能量分布特征

利用历史的表面漂流浮标资料研究了南极绕极流的平均结构、变化规律和能量特征。强劲的南极绕极流沿着纬向从西向东流动,并伴随着复杂多变的海洋锋面,主导着整个南大洋的海洋环流系统。首先,标准方差椭圆表明,阿加勒斯回流和东澳大利亚暖流是南极绕极流重要的流量补充。在南半球的冬季,南极绕极流的流速随着西风的增强而增强。在南极绕极流经向摆动的影响下,流核上的经向流速比纬向流速具有更加不稳定的特征。另外,南极绕极流从非洲南部开始自西向东逐渐减弱。其次,从能量的角度讨论了南极绕极流的细节特征。平均动能、扰动动能及其均方根在流核区域都很强,扰动动能和平均动能比值的趋势恰恰相反,强(弱)能量分布区域的涡旋耗散反而比较弱(强)。除了扰动动能和平均动能的比值之外,所有的能量形式都呈现了从西向东减弱的趋势。涡动耗散对南大洋北部的平均动能影响更大。     

用表层漂流浮标对海上溢油实时跟踪和监测的方法

一种适用于近海使用的表层漂流浮标,利用GPS定位,通过GSM/CDMA网络传输数据,是一种准确实时、成本低廉的环境监测和海流、污染跟踪工具。文章介绍几种溢油跟踪监测方法和特点、表层漂流浮标的设计及其在溢油漂移轨迹跟踪中应用的特点。     

便宜的自制GPS漂流浮标可成功刻画冬季广东沿岸流特征

本文介绍了一种旨在观测沿岸表层流的自制"表层海流实验"漂流浮标，该浮标基于GPS信号、简易且十分经济（每个约$30）。通过分析在大亚湾布放的六个漂流浮标轨迹和由此推算得到的流速发现，此类浮标基本可以刻画广东沿岸冬季表层流的特征。