This study is guided by other classifications of estuaries that are based on specified physical constraints. Previous classifications have been relevant and revealing of diagnostic functioning of estuaries in terms of their stratification and their baroclinically induced residual circulation. Those classifications, however, have disregarded residual circulations driven by tides, not only in estuaries, but in semienclosed basins in general. The classification proposed here uses tidally averaged, or residual, dynamics. Residual dynamics are explored via drivers, or forcing agents, of residual flow. Drivers are tides or density gradients and are counteracted by ‘modifiers,’ i.e., Earth’s rotation or friction. The relative influence between forcing agents is characterized by a scaled non-dimensional densimetric tidal Froude number, $F{r}_0^2$, which hinges on tidal current amplitude, water depth and reduced gravity. The competition between modifiers is determined by a non-dimensional Ekman number, Ek, which depends on the kinematic eddy viscosity, the latitude and the depth of the basin. The classification suggested identifies all types of estuaries, whose dynamics is influenced by density gradients, but also recognizes frictionless tidal basins, tidal rivers, coastal lagoons, and basins that switch their dynamics from being baroclinically forced to being tidally forced. This classification can also be interpreted as an assessment of the strength of mixing (in Ek) versus the strength of baroclinicity (in $F{r}_0^2$), which determines the residual flows in semienclosed basins. Additionally, the classification incorporates basins forced by wind stress and/or baroclinicity, and basins forced by wind stress and/or tides.

本研究以基于特定物理约束的其他河口分类为指导。以前的分类与河口的分层和斜压引起的残余循环有关，并揭示了河口的诊断功能。然而，这些分类忽略了潮汐驱动的残余环流，不仅在河口，而且在一般的半封闭盆地中。这里提出的分类使用潮汐平均或残差动态。通过剩余流量的驱动因素或强制代理探索剩余动态。驱动因素是潮汐或密度梯度，并被 '修饰符抵消,' 即地球的自转或摩擦。强迫因子之间的相对影响的特征在于缩放的无量纲密度潮汐弗劳德数，$F{r}_0^2$，这取决于潮汐流幅度、水深和重力减弱。改性剂之间的竞争由无量纲 Ekman 数Ek决定，Ek取决于运动涡粘性、纬度和盆地深度。建议的分类识别了所有类型的河口，其动态受密度梯度的影响，但也识别无摩擦的潮汐盆地、潮汐河流、沿海泻湖和盆地，这些盆地将其动力学从斜压强迫转变为潮汐强迫。这种分类也可以解释为对混合强度（以Ek 为单位）与斜压强度（以Ek 为单位）的评估。$F{r}_0^2$)，它决定了半封闭盆地中的剩余流量。此外，该分类还包括受风应力和/或斜压作用的盆地，以及受风应力和/或潮汐作用的盆地。