【作者】 项印玉；

【导师】 朱建荣；

【作者基本信息】 华东师范大学 ， 港口、海岸及近海工程， 2008， 硕士

【摘要】 本文应用三维ECOM模式,结合观测资料模拟陆架环流及长江河口盐水入侵。在此基础上,通过三个数值试验,研究陆架环流对长江河口盐水入侵的影响程度及其动力机制。主要成果如下:(1)基于三维数值模式ECOM,建立了一个高分辨率长江河口及邻近海区三维水动力、盐水入侵数值模式。运用模式对实测的潮位、流速、流向和盐度进行验证,验证结果良好。(2)利用已建立的模式,综合考虑各种动力因素,模拟冬季黄海东海环流。模拟结果表明,台湾暖流沿着闽浙近海向东北流动,直至长江口,在北上的过程中有两次向东偏转。苏北沿岸流流向东南,其表层强度和范围明显大于底层。受长江冲淡水的顶推作用,32°N以南水域流速逐渐减小。(3)控制试验的结果表明,北支盐水入侵最严重,南槽次之。由于北支盐水倒灌的存在,在大潮期南支及以下河段的盐度呈现高—低—高的马鞍型分布。在科氏力作用下,盐水入侵在口门附近造成的盐度锋面向西北倾斜,在北支及南支河段,河槽北侧的盐度比南侧高。垂向上,受斜压梯度力作用,底层盐水入侵强度高于表层。(4)去除外海开边界余水位和长江口外部分海区的斜压梯度力后,台湾暖流完全消失,长江口外的盐度舌状锋明显减弱。而苏北沿岸流有增强之势,将长江冲淡水向南压迫,导致北支口外的盐度锋南移,使北港盐度值增大,并驱使大量高盐水进入北支,使北支盐水倒灌增强。南槽的盐度梯度及盐度值降低。(5)苏北沿岸流在无风的情况下完全消失,苏北沿岸及北支的盐度值明显减小,北支口外的盐度锋明显减弱,北支盐水倒灌也因此减弱;而台湾暖流由于北上的阻力减弱,其流幅变宽,北上加深,使长江冲淡水的扩展方向整体向北偏转,导致南北槽及闽浙近海的盐度均升高。123°E以东水域受到北支及北港大部分淡水的冲淡作用,盐度略有降低。(6)在模式中去除风应力、外海开边界余水位及长江口外的斜压梯度力,在完全去除陆架总环流的情况下,试验结果显示,北支及北港的入海流量增加,使北支口的盐度锋向外海移动,苏北沿岸及北支的盐度明显降低;而南港的入海流量减少,使南港及闽浙近岸的盐度略有升高。台湾暖流消失,以及北港冲淡水向东南方向扩展增强,使长江口外122.5°E附近水域的盐度降低。数值试验的结果表明,长江口外陆架环流对盐水入侵和口外盐度分布起着重要的作用,是一个不能忽略的动力因子。更多还原

【Abstract】 In this thesis, making use of the three dimensional ECOM model and field data, shelf circulations in the East China Sea and the saltwater intrusion in the Changjiang Estuary are simulated. Based on the results, the impact of the shelf circulations in the East China Sea on the saltwater intrusion in the Changjiang Estuary is studied by three numerical experiments. The main fruits are as following.1. A three dimensional, high resolution, hydrodynamic and salinity numerical model in the Changjiang Estuary and its nearby areas is built up by using of the three dimensional ECOM model. Several field-measured elevation, current and salinity data are used to validate this model, and the result is reasonable.2. Based on the model which takes into account various dynamical factors, shelf circulations in Yellow Sea and East China Sea in winter are simulated exactly. The results show that, the Taiwan Warm Current flows northeastwards along the Min-Zhe Coast. Meanwhile, its direction turns to east twice obviously. It can arrive at the Changjiang Estuary. While the Subei Coastal Current flows southeastwards and the strength of its surface currents is bigger than the bottom currents. For the back pushing of the Changjiang River diluted water, current velocity is reduced gradually in the south of 32°N.3. The results of control numerical experiments show the saltwater intrusion in the North Branch is most serious, South Passage is the second. For Salt spilling over from the North Branch, salinity of the South Branch and its reaches presents a "high-low-high" saddleshaped pattern during spring tide. The salinity front induced by saltwater intrusion inclines northwestwards round the river mouth by the Coriolis force. In the North Branch and the South Branch, the saltwater intrusion at the north side is stronger than the south. The saltwater intrusion at the lower layer is stronger than the upper layer by the baroclinic pressure gradient force.4. The Taiwan Warm Current eliminated by omitting the residual water level and the baroclinic pressure gradient force at the river valley off the Changjiang Estruary and its north area, which weaken the ligulate front off the Changjinag Estruary. The Subei Coast Current is intensified and oppresses the Changjiang diluted water turn to south. Salinity front off the North Branch move to south, which increases the salinity in the North Channel and makes great high salinity water enter the North Branch causing the increment of the saltwater spilling over from the North Branch. Salinity in the South Passage is decreased for its diluted water is intensified.5. In no wind case, the Subei Coastal Current vanishes. The diluted water from the North Branch is intensified leading to the decrement in North Branch and the Subei Coast. The salinity front off the North Branch is weakened obviously, which decreases the saltwater spilling over from the North Branch. Because its resistance is weakened, the range of the Taiwan Warm Current becomes broad and it can deepened to flow northwards. The direction of the expansion of the Changjiang River diluted water turn to north, which cause the increment of the salinity in the South Passage, the North Passage and the Min-Zhe Coast. The salinity in the east of 122.5°E is decreased a little by the diluted water from the North Branch and the North Channel.6. Shelf circulations can be eliminated by omitting the wind stress, the residual water level and the baroclinic pressure gradient force off the Changjiang Estuary. The numerical experiment shows that, river flow from the North Branch and the North Channel is increasing, which makes the salinity front near the North Branch move to east. The salinity in the Subei Coast and the North Branch is obviously decreasing. Rive flow from the South Channel is decreasing, causing the increment of the salinity in the South Channel and the Min-Zhe Coast. Because the Taiwan Warm Current is eliminated and the southeastward expansion of diluted water from the North Channel is increased, the salinity near 122.5°E off the Changjiang Estuary is decreased.The numerical experiments show that, the shelf circulations off the Changjiang Estuary play an important role in saltwater intrusion and the salinity distributions off the estuary, so it is a noticeable dynamic factor.更多还原