Study of sea surface fluctuations in the Pacific on the basis of satellite altimetry data

卫星高度计可以直接测量海面高度的动力特性，对物理海洋学具有划时代的意义。本文分析了近年来的高度计资料，探讨了从盆地尺度到中尺度的宽波长范围的海面波动特征。结果如下：(1)基于精确重复任务头两年（1986- 1988）的Geosat高度计数据，检测了海面动力地形（SSDT）的时间波动；这里的SSDT是实际海面与大地水准面的偏离，其梯度给出海面的地转速度。在北太平洋西半部，发现了明显的西向相位传播。它们的相速与长斜压罗斯比波的理论值接近，但它们之间存在一些差异，这是最新理论无法解释的。(2)在相同资料的基础上，进一步表明黑潮伸展区充满了向西传播的明显的气旋和反气旋扰动。利用卫星海表温度资料证实了这些扰动具有斜压特征。位于黑潮延伸以南的黑潮逆流强度与黑潮延伸相关波动，因此黑潮延伸的季节周期似乎代表一个局部副环流（水平尺度为1,000-2,000 km）的波动，而不是整个北太平洋副热带环流的波动。(3)利用任务第一年（1992- 1993年）的TOPEX/Poseidon高度计数据，分析了日本南部黑潮轴的波动。近似绝对SSDT是由高度计资料和气候平均SSDT组合而成的。海面地转速度是根据其水平梯度估计的。结果与现场地表速度数据得到的黑潮轴位置波动进行了比较。比较表明，近似地转速度的分布可以可靠地描述黑潮轴的波动。少

Satellite altimeters can directly measure the dynamical property of sea surface height, and therefore are epoch-making for physical oceanography. In the present study, recent altimeter data are analyzed to investigate features of sea surface fluctuations for a wide wave-length range from the basin scale to the meso-scale. Followings are the results ;(1) On the basis of Geosat altimeter data from the first two years (1986-88) of the Exact Repeat Mission, temporal fluctuation of the sea surface dynamic topography (SSDT) is detected ; here the SSDT is the departure of the actual sea surface from the geoid and whose gradient gives the geostrophic velocity at the sea surface. There are found clear westward phase propagations in the fluctuation field of the SSDT in the western half of the North Pacific. Their Phase speeds are close to the theorretical value for the long baroclinic Rossby wave, but there are some discrepancies between them which cannnot be explained by the latest theory.(2) O … More n the basis of the same data, it is shown that the Kuroshio Extension region is filled with clear cyclonic and anti-cyclonic disturbances propagating westward. Those disturbances are confirmed to have baroclinic feature, using satellite sea surface temperature data. It is also shown that the intensity of the Kuroshio Countercurrent located south of the Kuroshio Extension fluctuates correlatively with the Kuroshio Extension, and therefore the seasonal cycle of the Kuroshio Extension seems to represent fluctuations of a local sub-gyre (with horizontal scales of 1,000-2,000 km), instead of the whole subtropical gyre of the North Pacific.(3) On the basis of TOPEX/Poseidon altimeter data from the first one year (1992-93) of the mission, fluctuations of the Kuroshio axis south of Japan are analyzed. Approximated absolute SSDT is derived from combination of the altimeter data and the climatological mean SSDT.Geostrophic velocities at the sea surface are estimated from its horizontal gradient. The results are compared with fluctuations of location of the Kuroshio axis derived from in situ surface velocity data. The comparison shows that the distribution of the approximated geostrophic velocity can describe the fluctuation of the Kuroshio axis reliably. Less