Upstream Extension of a Bottom-Advected Plume and Its Mechanism: The Case of the Yellow River
Upstream Extension of a Bottom-Advected Plume and Its Mechanism: The Case of the Yellow River
复制标题
底部平流羽流的上游延伸及其机制：以黄河为例
DOI：
10.1175/jpo-d-20-0235.1
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发表时间：
2021
影响因子：
3.5
通讯作者：
Zou Tao
中科院分区：
文献类型：
--
作者：
Yu Xiaojie;Guo Xinyu;Gao Huiwang;Zou Tao
水文调查表明，黄河羽流在低流量条件下的传播方向与开尔文波相反（上游），但随着流量的增加，转向下游。数值模拟再现了低流量条件下烟羽向上游延伸和高流量条件下烟羽向下游方向过渡的过程，证实了夏季风不是烟羽向上游延伸的必要条件。在小流量条件下，该模型还揭示了烟羽向上游延伸与潮差的关系：大潮时烟羽向上游延伸，小潮时烟羽向下游延伸。羽流的上游运动是淡水向上游输送的结果，淡水的上游输送取决于河口附近的上游潮致余流和离岸羽流前缘附近的下游密度驱动流。在河流流量较大的情况下，上游潮致余流不能与下游密度驱动流相竞争，羽流转向下游。动量分析证实了平流项和粘性项在小流量条件下的重要作用，以及在大流量条件下向科里奥利力主导系统的转变。一个理想化的模型研究表明，一个无量纲数的河流流量改变河流羽状延伸从上游到下游下，一个特定的上游环境流周围的河口。
Hydrographic surveys have revealed that the Yellow River plume propagates in the direction opposite to that of a Kelvin wave (upstream) under a low river discharge condition, but turns downstream as the river discharge increases. A numerical model reproduced the upstream extension of the plume under the low river discharge condition and the transition to the downstream direction under the high river discharge condition, and confirmed that the summer wind is not the necessary condition for upstream extension of the plume. With the condition of low river discharge, the model also indicated the dependence of the upstream extension of the plume on the tidal range: extending upstream in spring tide but turning downstream in neap tide. The upstream movement of the plume results from the upstream transport of freshwater that depends on the upstream tide-induced residual current around the river mouth and the downstream density-driven current around the offshore plume front. With the condition of high river discharge, the upstream tide-induced residual current cannot compete with the downstream density-driven current and the plume turns downstream. Momentum analysis confirms the important roles of advection term and viscosity term in the condition of low river discharge and the shift to a Coriolis force–dominated system under high river discharge condition. An idealized model study suggests a dimensionless number for the river discharge changing the river plume extension from upstream to downstream under a specific upstream ambient current around the river mouth.