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，在物理海洋学中具有划时代的意义。在本研究中，最近的高度计数据进行了分析，以调查从盆地尺度到中尺度的宽波长范围内的海面波动的特征。以下是结果：（1）根据精确重复使命头两年（1986- 1988年）的Geosat高度计数据，探测了海面动力地形（SSDT）的时间波动，SSDT是实际海面与大地水准面的偏离，其梯度给出了海面的地转速度。在北太平洋西半部的SSDT波动场中，存在明显的向西位相传播。它们的相速度接近于斜压Rossby长波的理论值，但它们之间存在着一些用最新理论无法解释的差异。(2)O ...更多信息 在相同资料的基础上，我们发现黑潮延伸区充满了向西传播的明显的气旋性和反气旋性扰动。利用卫星海温资料证实了这些扰动具有斜压特征。黑潮延伸区以南的黑潮逆流强度与黑潮延伸区的强度波动相关，因此黑潮延伸区的季节变化似乎代表了一个局部的亚环流（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1992 ~ 1993年的TOPEX/Poseidon高度计资料，分析了日本以南黑潮轴的变化。由高度计资料和气候平均SSDT的组合得到近似的绝对SSDT，由海面的水平梯度估算出海面的地转速度。将计算结果与现场实测的黑潮轴位置波动进行了比较。结果表明，近似的地转流速分布能够较好地描述黑潮轴的变化。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