Simpson's stratification index $\varphi$ is widely used in oceanography as an index of vertical stratification. However, the use of $\varphi$ can be problematic when the tidal amplitude is significant compared to the water depth, since $\varphi$ fluctuates periodically with the external tide even if the vertical density structure does not change. The stratification potential-energy anomaly $V$ is proportional to the square of the water column thickness $D$; therefore, $V^{\ast }={(H/D)}^{2}V$ (where $H$ is the mean water depth) is an appropriate standardized stratification index for estuaries and regions of freshwater influence. The usefulness of this index is demonstrated using time series $f_k={\left(H/D\right)}^{k}V\left(k=0,1,2,3\right)(f_0=V,f_1=H\varphi ,f_2=V^{\ast })$ and their power spectra as obtained from tower B3 in Isahaya Bay in Japan. Tidal cycle fluctuation is removed most effectively for $f_2(=V^{\ast })$.$$

辛普森的分层指数 $\varphi$在海洋学中被广泛用作垂直分层的指标。但是，使用$\varphi$ 当潮汐幅度比水深大时，可能会有问题，因为 $\varphi$即使垂直密度结构不变，其也会随着潮汐而周期性地波动。分层势能异常$V$ 与水柱厚度的平方成正比 $d$; 因此，$V^{\ast }={（H/d）}^{2}V$ （哪里 $H$是平均水深）是适合河口和淡水影响区域的标准标准化分层指数。使用时间序列证明了该索引的有用性$F_{ķ}={（H/d）}^{ķ}V（ķ=0，\mathrm{1个}，2，3）（F_0=V，F_{\mathrm{1个}}=H\varphi ，F_2=V^{\ast }）$从日本Is早湾B3塔获得的功率谱。最有效地消除了潮汐周期波动$F_2（=V^{\ast }）$。$$