西北太平洋反气旋涡的Argos浮标观测结果分析

Analysis of the anticyclone eddy in the Northwest Pacific with Argos drifters data

结合卫星高度计异常资料和2003年10月上旬投放在西北太平洋的25个Argos表层漂流浮标资料,分析观测海域的中尺度涡特征及浮标漂移路径上的温度和流速变化,结果表明:(1)7个浮标受强劲的黑潮流影响直接进入台湾岛以东黑潮表层的主流轴;(2)16个浮标在反气旋涡内旋转,并随中尺度涡向西运动,到达黑潮的东边界,由于中尺度涡旋的消亡,浮标脱离其影响后由黑潮带动向东海运动,浮标的移动轨迹呈螺线型;(3)仅有2个浮标在(123°E、20°N)附近通过吕宋海峡进入南海,且41490号浮标受台湾岛西南外海反气旋涡的影响作了2周旋转后再进入南海。比较分析表明,黑潮在冬季应该存在入侵南海的分支,但浮标能否顺利进入南海受多种随机因素控制,如风生流、潮流和波浪等。另外,西北太平洋向西传播的中尺度涡难以越过强劲的黑潮流屏障继续向西传播通过吕宋海峡进入南海。

Based on the Sea Surface Altimeter Anomaly data（SSHA） and 25 satellite-tracked surface Argos drifters deployed in the northwestern Pacific Ocean in early October 2003,the characteristics of meso-scale eddy to the east of Luzon strait and variability of temperature and velocity along the drifter trajectories are analyzed.The results show that：（1） 7 Argos drifters directly entered the surface Kuroshio axis east of Taiwan Island under the effect of the strong Kuroshio current.The moving velocity of the drifter contains low frequency component and high frequency oscillation of the tidal band.The low frequency component was influenced basically by the surface Kuroshio current,which is northward（northeastward） with a maximum flow velocity of 80 cm/s to the east of Taiwan,and a mean flow velocity of over 100 cm/s in the East China Sea.Sea surface temperature（SST） decreased linearly with the northward movement of the drifter.SST at the starting position was about 5 ℃ higher than that at the end position,which is resulted from the facts that the drifters moved from the warm low latitude area to the cold high latitude area,and the season changed from autumn to early winter,resulting the SST decreased gradually.（2） 16 Argos drifters revolved in the anticyclone eddy.They were affected by the eddy for about 1 month and their mean velocity was over 30 cm/s,and maximum velocity was over 75 cm/s.At the same time they moved westward with the meso-scale eddy before reaching the east boundary of the Kuroshio current to the east coast of Taiwan Island.With the eddy dissipation,they moved toward the East China Sea with the Kuroshio current.Some drifters were captured by large anticyclonic eddy to the east of Taiwan,and the trajectories showed spiral type of movement.The maximum flow velocity was 92.5 cm/s,and mean flow velocity reached 37.9 cm/s.Finally these drifters moved northward and entered the East China Sea.The velocity showed obvious difference in different region with a mean velocity of around 35 cm/s,and maximum over 100 cm/s.（3） Only 2 drifters entered the South China Sea（SCS） at（123°E,20°N）through the Luzon Strait.Both floats were affected by the same anticyclonic eddy before entering the SCS,and their trajectories are very similar.After breaking away from the anticyclonic eddy,one directly passed through the Luzon Strait with maximum velocity 140.1 cm/s and mean velocity 79.4 cm/s.The velocity decreased evidently after entering the SCS.The other drifter moved northward firstly with the Kuroshio current,and was captured by anticyclonic eddy to the east of Taiwan for 2 months.After leaving the eddy,it passed through the Luzon Strait and enters the SCS with maximum velocity 158.7 cm/s,and mean velocity 82.5 cm/s.The SST observed by the two floats also decreased with time owing to seasonal cooling.Comparing the trajectories of the drifters,most of them were affected by the same anticyclonic eddy to the east of the Luzon Strait.However their trajectories show obvious difference after leaving the eddy.Analysis shows that there should be a Kuroshio branch intruding into the SCS in winter,but whether or not a float can smoothly enter the SCS through the Luzon Strait is controlled by many stochastic factors,such as wind driven current,tidal current,waves and so on.It is difficult that the westward propagating eddies move cross the strong Kuroshio current barrier and pass through Luzon Strait into the South China Sea（SCS）.