Characteristics of variations of water properties and density structure around the Kuroshio in the East China Sea
Characteristics of variations of water properties and density structure around the Kuroshio in the East China Sea
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DOI：
10.1007/bf02823281
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发表时间：
1998-11
影响因子：
2.3
通讯作者：
E. Oka;M. Kawabe
中科院分区：
文献类型：
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作者：
E. Oka;M. Kawabe
分析了1988~1994年中国东海PN线季度场资料，分析了黑潮对水体性质和密度结构的影响。黑潮在PN线处流过大陆坡面。小于100db的表层水性质变化较大，表现出明显的季节变化周期，而次表层水性质变化较小。次表层较小的等压变化主要是由于等压线的垂直运动，其上的水性质变化不大。盐度、温度和等深的次表层变化可分为4个组，分别为：1组(上黑潮)、2组(上黑潮)、3组(下黑潮)和4组(下黑潮)。组1和组2(组3和组4)的平均等周期深度的差异与上(下)跃层黑潮速度的垂直切变高度相关。组1和组3的等水深的年周期很小(组3的季节内变化较大)，而组2和组4的等周期深度表现出明显的季节变化，秋季最小。结果表明，尽管黑潮流速的季节变化幅度和最大流速季节不同，但几乎每年的秋季都是最小的。等日深度的年际变化表现为第2群幅度大，第3、4群相反的位相，因此第1、2群与第3、4群的等日深度差，即黑潮流速的上、下切变，变化比较显著。
Quarterly data of CTD at the PN line in the East China Sea during 1988–94 were analyzed to examine the variations of water properties and density structure in relation to the Kuroshio. The Kuroshio flows over the continental slope at the PN line. Water properties in the surface layer less than 100 db change greatly and show a clear seasonal cycle, while those in the subsurface layer are much less variable. The small isobaric variations in the subsurface layer are almost due to the vertical movement of isopycnals, on which the water properties vary little. The subsurface variations of salinity, temperature and isopycnal depth are classified into four groups occurring in the four regions, divided vertically by the middle of the main pycnocline and horizontally by the offshore edge of the Kuroshio, named Groups 1 (upper Kuroshio), 2 (upper offshore region), 3 (lower Kuroshio), and 4 (lower offshore region). The difference in averaged isopycnal depth between Groups 1 and 2 (3 and 4) is highly correlated with the vertical shear of the Kuroshio velocity in the upper (lower) pycnocline. The isopycnal depth of Groups 1 and 3 has little annual cycle (with large intraseasonal variations in Group 3), while that of Groups 2 and 4 shows a clear seasonal variation with the minimum in fall. As a result, the Kuroshio velocity is smallest in fall almost every year, although the amplitude of seasonal variation and the season of maximum velocity are different from year to year. Interannual variations of isopycnal depth are characterized by a large amplitude of Group 2 and an opposite phase between Groups 3 and 4, so that the variations of difference in isopycnal depth between Groups 1 and 2 and Groups 3 and 4, i.e., the upper and lower shear of the Kuroshio velocity, are comparably significant.