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~C 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 tensiorneter 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
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.
The Taiwan Warm Current （TWC） and the Tsushima Warm Current （TSWC） flow northward over the shelf in the East China Sea （ECS）, which some previous studies regard as a Taiwan-Tsushima Warm Current （TTWC） System. But the roles of the TWC and TSWC in the formation of the TTWC system have not been clarified. This article will show that the TSWC is more important in the TTWC system. Using a three-dimensional baroclinic model, we conducted several numerical experiments to reveal the dynamic relationship between the TWC and TSWC. The results show that the TWC has little effect on the TSWC, while the TSWC has a significant effect on the TWC. A source-sink driven mechanism along isobaths may be used to explain this phenomenon The perennial northward flow through the Tsushima Strait pumps the response over the northern shelf in the ECS that gives rise to the TWC. Although the TSWC is located at the ＂downstream＂ region, it could induce about 0.5 Sv to TWC in annual mean values.
By combining Argos drifter buoys and TOPEX/POSEIDON altimeter data, the time series of sea-surface velocity fields in the Kuroshio Current (KC) and adjacent regions are established. And the variability of the KC from the Luzon Strait to the Tokara Strait is studied based on the velocity fields. The results show that the dominant variability period varies in different segments of the KC: The primary period near the Luzon Strait and to the east of Taiwan Island is the intra-seasonal time scale; the KC on the continental shelf of the ECS is the steadiest segment without obvious periodicity, while the Tokara Strait shows the period of seasonal variability. The diverse periods are caused by the Rossby waves propagating from the interior ocean, with adjustments in topography of island chain and local wind stress.
