The Balance of Salinity Variance in a Partially Stratified Estuary: Implications for Exchange Flow, Mixing, and Stratification
The Balance of Salinity Variance in a Partially Stratified Estuary: Implications for Exchange Flow, Mixing, and Stratification
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DOI：
10.1175/jpo-d-18-0032.1
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发表时间：
2018-12
影响因子：
3.5
通讯作者：
Tao Wang;W. Geyer
中科院分区：
文献类型：
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作者：
Tao Wang;W. Geyer
盐度方差耗散通过盐度方差平衡方程与交换流有关，同时其大小也与河口内湍流的产生和层结成正比。随着河流流量的增加，河口体积综合盐度方差耗散增加，由于更多的方差输入的开放边界的交换流和河流流量的驱动。这对应于由于河流流量较高的分层加剧，湍流产生向盐度方差消散的转化效率提高。在整个小潮周期中，盐度方差耗散的时间变化更多地依赖于层结而不是湍流的产生，因此在小潮向大潮的过渡期间，盐度方差耗散达到最大值。在大潮向小潮过渡的大部分时间内，来自开边界的盐度方差平流输入大于耗散，导致方差净增加，主要表现为垂向方差，即层化。层化的加强反过来又增加了盐度方差的耗散。在小潮期间，盐跃层附近的内部剪切应力引起了大量的盐度方差耗散增强。在小潮向大潮过渡的大部分时间里，耗散大于平流输入，盐度方差减小，层结被破坏。
Salinity variance dissipation is related to exchange flow through the salinity variance balance equation, and meanwhile its magnitude is also proportional to the turbulence production and stratification inside the estuary. As river flow increases, estuarine volume-integrated salinity variance dissipation increases owing to more variance input from the open boundaries driven by exchange flow and river flow. This corresponds to the increased efficient conversion of turbulence production to salinity variance dissipation due to the intensified stratification with higher river flow. Through the spring–neap cycle, the temporal variation of salinity variance dissipation is more dependent on stratification than turbulence production, so it reaches its maximum during the transition from neap to spring tides. During most of the transition time from spring to neap tides, the advective input of salinity variance from the open boundaries is larger than dissipation, resulting in the net increase of variance, which is mainly expressed as vertical variance, that is, stratification. The intensified stratification in turn increases salinity variance dissipation. During neap tides, a large amount of enhanced salinity variance dissipation is induced by the internal shear stress near the halocline. During most of the transition time from neap to spring tides, dissipation becomes larger than the advective input, so salinity variance decreases and the stratification is destroyed.