东海PN断面水团分布的季节变化

Seasonal Variation of the Water Mass Distribution Along the PN Section in the East China Sea

利用PN断面的高分辨率CTD温度、盐度和密度资料,采用曲线族拟合的水团分析方法分析发现,PN断面处的水团有明显的陆架水和黑潮水的交汇特征,且随着季节的变化PN断面处的水团特征也发生明显的变化。夏季,黑潮水核心离陆架的距离最远且深度较深,陆架水与黑潮的混合水浮置于黑潮水本体之上且向深海拓展的最远,隶属度在PN断面上200 m的分布几乎呈水平状;秋季,黑潮水主体离陆架的距离最近,并将陆架混合水向陆架压迫,使得隶属度等值线由夏季的平直状态向陆地弯曲;冬季,黑潮水团的核心占据了深海区域的整个表层和次表层,且位置相对于秋季更向深海移动,黑潮水与陆架水的交汇处也由秋季的陆架移向陆坡;春季,是唯一可以清楚地看到陆架混合水隶属度分布的季节,此时陆架混合水充满整个陆架海域,而黑潮水的核心进一步远离陆架。海面风场和净热通量场通过改变混合层的深度影响PN断面处黑潮水和陆架水之间的混合,而海面降水对于PN断面上的水团分布特征没有显著影响。

By using the hydrographic CTD data and the curve membership function water mass analysis method, the water mass character is given. It is found that the water mass character in the PN section is affected by both the continental shelf water and the Kuroshio water, and there is obvious seasonal variation on water mass character. In summer, the continental shelf water stretches towards the deep sea and floats over Kuroshio, the core of the Kuroshio reaches the furthest position of a year, the isoclines of curve membership function assumes almost horizontal; In autumn, Kuroshio is nearest the continental shelf, the encountering area of them is suppressed to the continental shelf; In winter, both Kuroshio and the continental shelf water move towards the deep sea, and the encountering position is deep enough to influence the pycnocline in the deep sea; In spring, the encounter position of the two water masses moves towards the deep sea relative to winter, and it is the only season that can see the curve membership function value of continental shelf water. The sea surface wind stress and net heat flux affect the seasonal variation of water mass character in the PN section by changing the mixed layer depth every season. While there is no obvious influence from precipitation to the season varia- tion of water mass distribution.