夏季长江口与苏北海域之间的水体运动及其对动力因子的响应

摘要: 基于一个高分辨率的三维数值模式，定量化研究了夏季长江口与苏北海域之间的水体运动规律，探讨了季风和潮汐等外部动力因子对该海域水体运动的影响，并计算了苏北特定断面上的水体通量、长江淡水通量和苏北河流淡水通量.数值模拟结果表明，在气候态条件下，苏北海域水体净输运整体向北，苏北浅滩附近的水体净输运速度为10 cm/s，射阳河口附近水体产生离岸净输运速度，而沿40m等深线的水体净输运速度为7 cm/s左右.苏北近岸水体通量具有大小潮变化，小潮时断面水体通量最小，大潮时水体通量最大.潮汐对于长江口与苏北海域之间的水体运动具有巨大的影响，当没有潮汐作用时，长江口以北海域水体净输运均向北，沿40m等深线的东南方向水体输运现象消失；季风对于该海域的水体运动没有显著影响，仅仅改变了局部区域的水体输运量.
- 长江口与苏北海域 /
- 水体运动 /
- 动力因子 /
- 数值模拟
Abstract: The objective of this study was to investigate summertime water movement and its response to wind and tidal forces between the Changjiang Estuary and the Subei coastal area based on a high-resolution, three-dimensional numerical model. The volumetric flux and the freshwater transport from the Changjiang River and the Subei local rivers were quantified across a number of cross-shelf sections. The results indicated that, under the studied climatologic conditions, the net transport in the Subei Coastal Water is generally northward. The velocity of this northward transport reaches 10 cm/s in the shallow area. Offshore transport occurs in the vicinity of the Sheyang Estuary, with a net transport velocity of circa 7 cm/s along the 40 m isobaths. The sectional water flux is related to the tidal range, which reaches a low point in neap tide and a high point in spring tide, respectively. The tide has great impact on water movement in this area. Without the tide, the net water transport is entirely northward north of the Changjiang River Estuary and the southeastward transport along the 40 m isobaths vanishes. On the other hand, the monsoon has no significant influence on the water movement; it only adjusts the water transport in a few local areas.
- Changjiang Estuary and Subei coastal area /
- water movement /
- dynamic factor /
- numerical simulation

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图 1 研究区域地形图

注: 由南向北四个断面分别为a、b、c和d断面

Fig. 1 Topography of the study area

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图 2 模型网格范围

Fig. 2 Mesh scope of the numerical model

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图 3 M$_{2}$分潮同潮图

注: 蓝色实线为等相位线, 间隔为30$^\circ$; 红色虚线为等振幅线, 间隔为20 cm

Fig. 3 Cotidal chart of M$_{2}$ tidal constituent

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图 4 夏季表层流场

Fig. 4 Surface currents in summer

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图 5 夏季表层盐度场

注: 左表示气候态条件, 中表示无风条件, 右表示无潮汐条件; 实线为等盐度线, 间隔为1 psu, 其中, 红色实线为30 psu等盐度线; 黑色虚线为40 m等深度线

Fig. 5 Surface salinity in summer

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图 6 夏季长江淡水表层示踪剂浓度场

注: 彩色为示踪剂浓度, 黑色虚线为40 m等深度线, 图 7同

Fig. 6 Surface tracer concentration of Changjiang freshwater in summer

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图 7 夏季苏北河流淡水表层示踪剂浓度场

Fig. 7 Surface tracer concentration of Subei freshwater in summer

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图 8 垂向平均的水体净输运速度

注: 左表示气候态条件, 中表示无风条件, 右表示无潮汐条件

Fig. 8 The vertically-averaged net transport velocity

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图 9 水体断面通量

注: 黑线为气候态条件, 绿线为无风条件, 红线为无潮汐条件; 由上至下分别为a、b、c和d断面; 左边的阴影区间表示小潮时期, 右边阴影区间则为大潮时期. 图 10和图 11同

Fig. 9 Sectional water flux

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图 10 长江淡水断面通量

Fig. 10 Sectional flux of Changjiang freshwater

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图 11 苏北河流淡水断面通量

Fig. 11 Sectional flux of Subei freshwater

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