Mixing Estimates for Estuaries
Mixing Estimates for Estuaries
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DOI：
10.1175/jpo-d-18-0147.1
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发表时间：
2019-02-01
影响因子：
3.5
通讯作者：
MacCready, Parker
中科院分区：
文献类型：
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作者：
Burchard, Hans;Lange, Xaver;MacCready, Parker
著名的克努森关系和总交换流量（TEF）分析框架提供了通过开放边界到邻近海洋的交换流量的量化，以体积值（克努森理论：流入和流出体积或盐度）或盐度空间的分辨率（TEF：盐度坐标中的体积和盐通量分布）。在本研究中，这些理论扩展到混合的盐度，定义为由于湍流混合的盐度方差的衰减。除了平流通量外，现在还考虑了边界扩散通量。这些新的努森和TEF关系的混合推导出应用高斯定理的盐度平方和盐度方差方程。作为分析的结果，四个不同的努森关系的混合在河口导出。第一个是准确的，并考虑非周期性以及非恒定的流入和流出盐度。其他三个配方只是近似的，在这个意义上，无论是非周期性或非恒定性或两者都放松。MacCready等人最近推导出了其中最简单的公式，并将河口混合估计为流入盐度、流出盐度和时间平均河流径流的产物。这四个混合估计系统地评估了一些理想化的河口测试情况。对于周期性潮流，最简单的估计仍然预测有效的（物理加数值）混合误差约为10%。
The well-known Knudsen relations and the total exchange flow (TEF) analysis framework provide quantifications of exchange flow across an open boundary to the adjacent ocean in terms of bulk values (Knudsen theory: inflow and outflow volume or salinity) or with resolution in salinity space (TEF: profiles of volume and salt flux in salinity coordinates). In the present study, these theories are extended toward mixing of salinity, defined as the decay of salinity variance due to turbulent mixing. In addition to the advective fluxes, diffusive fluxes across the boundary are also considered now. These new Knudsen and TEF relations for mixing are derived by applying Gauss's theorem to the salinity square and salinity variance equations. As a result of the analysis, four different Knudsen relations for the mixing in estuaries are derived. The first one is exact and considers nonperiodicity as well as nonconstancy of the inflow and outflow salinities. The other three formulations are approximate only, in the sense that either nonperiodicity or nonconstancy or both are relaxed. The simplest of those formulations has recently been derived by MacCready et al. and estimates the estuarine mixing as the product of inflow salinity, outflow salinity, and time-averaged river runoff. These four mixing estimates are systematically assessed by means of a number of idealized estuarine test cases. For periodic tidal flow, the simplest estimate still predicts the effective (physical plus numerical) mixing within an error of about 10%.