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远区台风对长江口波浪动力的作用机制
任剑波1, 何青1, 沈健2, 徐凡1, 郭磊城1, 谢卫明1, 朱磊3
1.华东师范大学河口海岸学国家重点实验室;2.美国威廉玛丽学院弗吉尼亚海洋研究所 美国 弗吉尼亚州;3.中山大学海洋科学学院 广州
摘要:
陆架远区台风对河口波浪动力场的影响是以往河口动力研究的弱点。本文利用第三代波浪模式SWAN计算了远区台风“三巴”期间长江口波浪动力场,分析了陆架至河口区的波能耗散和波致泥沙侵蚀率的时空分布,结果表明:(1)白帽破碎是维持深水区波浪能量平衡和限制波高成长的主要机制,底摩擦耗能和水深诱导的破碎耗能是长江口横沙东滩和崇明东滩邻近海域波高减小的主要原因;(2)远区台风期间,波浪切应力的分布与相对水深有关,涌浪是导致河口区波浪切应力增大的主要原因;(3)台风浪产生的泥沙侵蚀率是常规天气下潮流侵蚀率的15倍,证明与河口相距数百公里的远区台风仍然能够对长江口波浪动力产生明显影响;(4)当长江口三角洲前缘风速达到约10 m/s时,远区台风引起的波浪在-5 - -10 m等深线及邻近水域具有显著的掀沙能力。研究揭示了远区台风对波浪和泥沙侵蚀的动力作用特征和机制,涌浪由外海向近岸传播过程中,由于波-波相互作用,能量由高频向低频转换,周期和波长逐渐增大,近底层轨道流速增大,能量密度增高,对泥沙侵蚀起主导作用,该研究成果对深化认识远区台风对长江口动力环境、地貌演变、航运和滩涂保护等有重要科学意义。
关键词:  远区台风  波浪切应力  长江口  波浪侵蚀
DOI:10.11759/hykx20200118001
分类号:
基金项目:国家自然科学基金项目(51739005),科技部项目(2016YFE0133700);上海市科委重点基金项目(18DZ1204800,18DZ1206400)
The mechanism of a remote typhoon on wave dynamics in the Changjiang Estuary
Ren jianbo1, He qing1, Shen jian2, Xu fan1, Guo Leicheng1, XIe weiming1, ZHu lei3
1.State Key Laboratory of Estuarine and Coastal Research, East China Normal University;2.virginia institute of marine science;3.School of Marine Science, Sun Yat-sen University, 135 Xingangxi Road, Guangzhou, China
Abstract:
The influence of remote typhoon on wave dynamics in Estuary was a weakness issue. In this paper, a third generation wave model SWAN was conducted to calculate wave dynamics field in the Changjiang Estuary (CJE) during typhoon "Sanba", we analyzed the spatial and temporal distributions of wave energy dissipation and sediment erosion rate and concluded :(1) The whitecapping dissipation was the main mechanism to maintain wave energy balance in deep water and limit wave growth, while bottom friction and depth-induced dissipation were the main causing for decrease of wave height in shallow waters near Hengsha east shoal and Chongming east shoal. (2) The distribution of wave shear stress was related to the relative depth, swells dominated the increase of wave shear stress. (3) The wave-induced sediment erosion rate during remote typhoon was 15 times that of tide-induced ones, in implied that the remote typhoon could have significant impact on the wave dynamics in the CJE. (4) Typhoon-induced waves could obviously resuspend sediment in the water area between -5 and -10 m isobaths, when wind speed in the delta front of the CJE was greater than 10 m/s. This paper revealed the mechanism of a remote typhoon on wave dynamics in the CJE, wave period and length increased as well as energy density due to frequency shift from high frequency to low frequency, when swells propagated from open sea to coast area, swells played a key role in increasing orbital velocity and erosion. The results were of significance for understanding of dynamic environment, geomorphology, navigation and tidal flat protection of the CJE under typhoon conditions.
Key words:  Remote typhoon  Wave shear stress  The Changjiang Estuary  wave-induced sediment erosion.
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