The Yellow Sea Warm Current(YSWC) penetrates northward along the Yellow Sea Trough,and brings warm and saline water towards the Bohai Sea.The YSWC becomes much less intrusive in summer and is limited mostly in the southern trough,contrasting with a deep winter penetration well into the trough.The seasonal variability of the YSWC has prompted a debate regarding which controls the YSWC and its seasonal variability.In this article,the annual mean and seasonal variability of the YSWC was examined by using a 3-D ocean model together with several experiments.The results show that in the annual mean the YSWC is a compensating current firstly for the southward Korea Coastal Current(KCC),which is mainly caused by the Kuroshio Current(KC).The local wind-stress forcing plays an important but secondary role.However,the local monsoonal forcing plays a prominent role in modulating the seasonal variability.A deep northwestward intrusion of the YSWC in winter,for instance,is mainly due to a robustly developed China Coastal Current(CCC) which draws water along the Yellow Sea trough to feed a southward flow all the way from the Bohai Sea to the Taiwan Strait.
Atmospheric response to SST variability was estimated using generalized equilibrium feedback analysis (GEFA) in the SST EOF space with synthesis data from an idealized climate model. Results show that the GEFA atmospheric response to the leading SST EOF modes is much more accurate and robust than the GEFA feedback matrix in physical space. Therefore, GEFA provides a practical method for assessing atmospheric response to large-scale SST anomalies in terms of the leading EOFs.
采用1958～2002年海洋同化资料SODA（Simple Ocean Data Assimilation）的海温场，定义了东印度洋。西太平洋永久性暖池（简称印．太暖池）指数，即不随季节变化的27．5℃等温面所包含的〉27．5℃的暖水体积或强度，并采用功率谱和小波分析的方法研究了其周期变化特征。结果表明，印度洋暖池和西太平洋暖池均具有显著的准10a的周期振荡和1976～1986年前后的年代际突变特征，暖池由1976年前的“冷”暖池转变为1986年后的“热”暖池；暖池指数的季节循环也存在显著的年代际突变特征，特别是西太平洋暖池在异常暖年代其季节变化还呈现出明显的增暖趋势；暖池三维结构的年代际变化主要表现为在暖年代热带南印度洋暖水的向西向南扩张和西太平洋暖池东边界的向东及北边界的向北扩张，暖异常主要分布在60m以浅的上混合层中暖池的东边界区域，而其下面的温跃层内则为更强的异常降温，垂向上表现出上暖下冷的斜压模态结构，而温跃层和混合层深度的变化在不同暖池区则有不同的特点，表明东印度洋暖池和西太平洋暖池的年代际变化可能由不同的机制引起，尚需进一步分析其海洋动力学和热力学过程。
Near-inertial waves(NIWs), which can be generated by wind or the parametric subharmonic instability(PSI) of internal tides, are common in the South China Sea(SCS). Moored current observations from the northern SCS have revealed that the PSI of semidiurnal(D_2) internal tides is another source of NIWs. The objective of this study was to examine the energy variance in the PSI of D_2 tides. The PSI of D_2 internal tides generated NIWs and waves with frequencies around the difference frequency of D_2 and f. The observed NIWs induced by PSI could be distinguished clearly from those elicited by typhoon Krosa. Shortly after Krosa entered the SCS, NIWs began to intensify on the surface and they propagated downward over subsequent days. The near-inertial currents were damped quickly and they became relatively weak before the waves were reinforced beneath the mixed layer when wind stress was relatively weak. Rotation spectra indicated an energy peak at exactly the difference frequency D_2–f of the NIWs and D_2, indicating nonlinear wave-wave interaction among D_2, f, and D_2–f. Depth-time maps of band-pass fi ltered velocities of D_2 –f showed the waves amplifi ed when the NIWs were reinforced, and they intensifi ed at depths with strong D_2 tides. The energies of the NIWs and D_2 –f had high correlation with the D_2 tides. The PSI transferred energy of low-mode D_2 internal tides to high-mode NIWs and D_2–f waves. For the entire observational period, PSI reinforcement was observed only when mesoscale eddies emerged and when D_2 was in spring tide, revealing a close connection between mesoscale eddies and NIWs. Mesoscale eddies could increase the energy in the f-band by enhancing the PSI of D_2 internal tides. Thus, this represents another mechanism linking the energy of mesoscale eddies to that of NIWs.
A new instrument for upper ocean survey, namely the UCTD (Underway Conductivity-Temperature-Depth), which combines some of the advantages of other underway instruments, is introduced in this paper. The Introduction section presents a description of the construction and function of the UCTD, and the experiments conducted in the South China Sea on board the R/V Dong Fang Hong 2 in July 2007 and August 2008. The UCTD system, with pressure and temperature sensors in the probe, is con- veniently portable, cost-effective and environment-friendly. It is hopefully suitable for future cruises. An intercomparison based on regressing with the experiment temperature data from both SeaBird plus911 CTD and the UCTD showed that the standard deviation is 0.88℃ and the correlation coefficient is 0.96, achieving the goals set for the current oceanography uses. In the hydrodynamic experiments, the descending velocities and depths were calculated for different ship speeds. A pulling test was designed with a tensiometer to measure the magnitude of the pull. The maximal tension of the line was found to be 66.2 kg, which is far lower than the bearing limit of the Hollow Spectra line. Finally, some improvement suggestions are put forward for future experiments and production.
SONG XiangzhouLI HuiLIN XiaopeiCHEN XueenGUO XinshunTIAN Jiwei
