The 4-D structure of upwelling and Pearl River plume in the northern South China Sea during summer 2008 revealed by a data assimilation model
The 4-D structure of upwelling and Pearl River plume in the northern South China Sea during summer 2008 revealed by a data assimilation model
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DOI：
10.1016/j.ocemod.2011.01.002
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发表时间：
2011
期刊：
影响因子：
3.2
通讯作者：
Y. Shu;Dongxiao Wang;Jiang Zhu;S. Peng
中科院分区：
文献类型：
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作者：
Y. Shu;Dongxiao Wang;Jiang Zhu;S. Peng
利用资料同化技术分析了2008年夏季南海北方上升流和珠江羽流的四维结构。在普林斯顿海洋模式中采用了一种Encavity Kalman Smoother方案。结果表明，珠江羽流轴沿着表层流向东延伸至台湾沿岸，并在（116°E，22.6°N）和（117.6°E，22.8°N）附近两次转向离岸，最后到达台湾海峡。盐度沿着羽状流轴的垂直剖面表明，珠江淡水对10- 20 m深度的盐度分布有影响。上层异常暖水的出现，可能是由于116°E以西的上升流被淡水柱所覆盖，导致层化加剧，垂直混合受到抑制。从有利到不利的上升流变化的风可以在模式域的中心诱导低盐度水透镜。南海上升流最早出现在珠江口以东114.5°E，然后向东增强，在汕头附近（116.7°E，23.2°N）达到最大值。由于汕头大陆架较宽，流致上升流主要出现在汕头地区，因此，即使7月4日汕尾地区的上升流顺风使其停止，汕头地区的上升流仍然存在。此外，由于大尺度流的方向有利于南海上升流的发展，且在短时间内不可能通过改变当地风的大小而逆转，因此汕头地区风致和流致上升流的上升流停止时间要比汕尾地区以风致上升流为主的上升流的停止时间长。汕尾较陡的坡度也缩短了那里的上升流停止时间。
We analyze four-dimensional structures of upwelling and Pearl River plume in the northern South China Sea (NSCS) during the summer of 2008 based on data assimilation. An Ensemble Kalman Smoother scheme is employed in the Princeton Ocean Model. It is found that the Pearl River plume axis extended eastward along with the surface current to the coast of Taiwan and swerved offshore twice near (116°E, 22.6°N) and (117.6°E, 22.8°N) before reaching the Taiwan Strait. The vertical transect of salinity along the plume axis indicates that the Pearl River freshwater could affect salinity distribution down to a depth of 10–20m. Anomalously warm water is found in the upper layer, which could be attributed to the intensified stratification and suppressed vertical mixing caused by the freshwater of the plume capping the upwelling west of 116°E. The varying winds from upwelling favorable to unfavorable could induce a low-salinity water lens at the center of the model domain. Upwelling in the NSCS initially occurred at 114.5°E, to the east of the Pearl River Estuary, intensified eastward, and reached its maximum near Shantou (116.7°E, 23.2°N). Since current-induced upwelling appeared mainly in Shantou due to a wide shelf, it is found that even if the wind-induced upwelling was shut down in Shanwei by upwelling favorable wind on July 4, the upwelling still existed in Shantou. Moreover, because the direction of large-scale current was in favor of upwelling in the NSCS that cannot be reversed by varying local winds over a short time period, the upwelling shutdown time is longer for both wind-induced and current-induced upwelling in Shantou than for mainly wind-induced upwelling in Shanwei. The steeper slope in Shanwei also shortens the upwelling shutdown time there.