Seasonal variability of the Kuroshio Current at the PN Section in the East China Sea based on in-situ observation from 1987 to 2010
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摘要: 由于黑潮流场的时空变化受中尺度涡的影响非常显著, 我们需要长期的观测资料来准确的描述其流场的季节变化特征。因此, 我们收集了PN断面1987-2010年的地转流资料, 以及1993-2008年的船载ADCP资料, 并基于这些资料对PN断面的黑潮流场的季节变化特征进行了分析。两类观测资料均给出黑潮在PN断面三个不同区域具有显著的季节变化, 这三个区域分别位于黑潮流场的中心以及两侧。其对应的季节变化具体表现为黑潮中心区域的流速在秋季最小, 黑潮右侧的逆流在春季最强, 黑潮左侧的流速在秋季最强而在冬季最弱。船载ADCP资料揭示, 相对于垂直于PN断面的黑潮流场而言, 平行于PN断面的流场在表层的季节变化成分相对微弱。进一步的分析表明, PN断面黑潮流场的季节变化和上游、下游的流场变化紧密相关。Abstract: As the spatio-temporal variability of the Kuroshio is highly influenced by mesoscale eddies, representing its seasonal variability characteristics requires sufficiently long term observations to reduce the uncertainties. Geostrophic velocity data estimated from hydrographic observation from 1987 to 2010 and the shipboard ADCP velocity data from 1993 to 2008 at the PN Section in the central East China Sea are collected to view the seasonal variability objectively. From both types of observation, it is found that the seasonal climatology mean of the Kuroshio Current exhibits significant difference in three areas, which are located at the Kuroshio Current core and its two flanks in a shallow layer less than 300 m, with the weakest northeast current at the core in autumn, the strongest counter current on the right flank in spring, and the strongest northeast current on the left flank in autumn, respectively. The seasonal variance of the Kuroshio Current also exhibits significant difference on the off-shore side of the Kuroshio, with larger variance in spring and summer while smaller variance in autumn and winter. For the current parallel to the PN Section, the ratio of the seasonal variability component to the intraseasonal variability component is relatively smaller than that for the current perpendicular to the PN Section. Further analyses indicate that the seasonal variability at the PN Section is tightly linked to the upstream and downstream current variability.
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Key words:
- Kuroshio Current /
- seasonal variability /
- East China Sea /
- significance test
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