The Kuroshio Extension Region (KER) has the most active oceanic mesoscale eddies within the North Pacific Ocean, nevertheless, there is a lack of observations on the three-dimensional (3D) fine structure of these eddies. Satellite altimeter data and underway observations were used in combination to conduct a fine-scale characterisation of the 3D thermohaline structure and circulation of a mesoscale cyclonic eddy within the KER during June, 2014. The results showed that isotherms in the six in situ sections consistently exhibited enhanced upward bending and negative temperature anomalies were distinct. At locations closer to the centre of the eddy, the negative temperature anomalies became more significant and the intensity of the cold core became more pronounced. The isohalines also trended upwards, with the upper and lower levels having negative and positive anomalies, respectively. The isohalines at the various layers similarly exhibited a clear eddy-like structure from the subsurface down to 1,000 m. Both the actual flow field measured by the Acoustic Doppler Current Profiler (ADCP) and the geostrophic flow field based on thermohaline data indicated a significant asymmetric cyclonic circulation structure. By comparing with the in situ data, the HYbrid Coordinate Ocean Model (HYCOM) is capable of depicting the mesoscale eddy while the magnitude and eddy location deviate from in situ observations.

黑潮扩展区（KER）具有北太平洋中最活跃的海洋中尺度涡旋，但是，缺乏关于这些涡旋的三维（3D）精细结构的观测资料。结合卫星高度计数据和进行中的观测结果，对2014年6月KER的3D热盐结构和中尺度旋风涡旋进行了精细的表征。结果表明，六个原位剖面的等温线始终呈现向上弯曲和负温度异常明显。在靠近涡流中心的位置，负温度异常变得更加明显，冷芯的强度变得更加明显。等值线也呈上升趋势，上层和下层分别具有负异常和正异常。从地下到1000 m，各层的等值卤水同样表现出清晰的涡状结构。由声学多普勒电流剖面仪（ADCP）测量的实际流场和基于热盐数据的地转流场都表明存在明显的非对称旋风循环结构。通过与原位数据进行比较，Hybrid坐标海洋模型（HYCOM）能够描述中尺度涡旋，而震级和涡旋位置却与原位观测值有所不同。由声学多普勒电流剖面仪（ADCP）测量的实际流场和基于热盐数据的地转流场都表明存在明显的非对称旋风循环结构。通过与原位数据比较，Hybrid坐标海洋模型（HYCOM）能够描绘中尺度涡，而震级和涡位置则与原位观测值有所不同。由声学多普勒电流剖面仪（ADCP）测量的实际流场和基于热盐数据的地转流场都表明存在明显的非对称旋风循环结构。通过与原位数据比较，Hybrid坐标海洋模型（HYCOM）能够描绘中尺度涡，而震级和涡位置则与原位观测值有所不同。