In the region southeast of Okinawa, during May to July 2001, a cyclonic and an anticyclonic eddy were observed from combined measurements of hydrocasts, an upward-looking moored acoustic Doppler current profiler (MADCP), pressure-recording inverted echo sounders (PIESs), satellite altimetry, and a coastal tide gauge. The hydrographic data showed that the lowest/highest temperature (T) and salinity (S) anomalies from a 13-year mean for the same season were respectively ?3.0/+2.5°C and ?0.20/+0.15 psu at 380/500 dbar for the cyclonic/anticyclonic eddies. From the PIES data, using a gravest empirical mode method, we estimated time-varying surface dynamic height (D) anomaly referred to 2000 dbar changing from ?20 to 30 cm, and time-varying T and S anomalies at 500 dbar ranging through about ±2 and°C ±0.2 psu, respectively. The passage of the eddies caused variations of both satellite-measured sea surface height anomaly (SSHA) and tide-gauge-measured sea level anomaly to change from about ?20 to 30 cm, consistent with the D anomaly from the PIESs. Bottom pressure sensors measured no variation related to these eddy activities, which indicated that the two eddies were dominated by baro-clinicity. Time series of SSHA map confirmed that the two eddies, originating from the North Pacific Subtropical Countercurrent region near 20°–30°N and 150°–160°E, traveled about 3000 km for about 18 months with mean westward propagation speed of about 6 cm/s, before arriving at the region southeast of Okinawa Island.
2001年5～7月,在冲绳岛以东海区,我们通过CTD(conductivity temperature and depth)、锚系海流剖面、PIES(pressure-recording inverted echo sounders)、卫星海面高度计和沿岸潮位仪的组合观测到一个气旋涡和一个反气旋涡.CTD断面数据显示,气旋涡和反气旋涡中心位于380/500dbar水深,对应的温度(T)和盐度(S)距平分别为-3.0/+2.5℃和-0.20/+0.15.从PIES数据,我们估算了气旋涡和反气旋涡经过时,相对于2000dbar深基准的动力高度(D)的时间变化为-20～30cm,500dbar深的T和S距平的变化范围约±2℃和±0.2.同时,由卫星海面高度计和潮位仪观测得到的海面高度距平变化范围约为-20至30cm,与PIES观测到的D的变化基本一致.由于两个涡经过时,PIES的压力传感器没有显示出相应的变化,反映出这两个涡具有较强的斜压特性.从卫星海面高度距平时间序列图追溯确认,这两个涡起源于北太平洋副热带逆流区附近,即20°～30°N,150°～160°E海区.它们以6cm·s-1的平均速度向西传播了约3000km,历时约18个月,然后抵达冲绳岛以东海区.
