The impact of buoyant discharge variations on the dynamics of coastal buoyancy-driven currents is studied using a primitive equation numerical model (SPEM5). First, variable discharge is introduced as harmonic fluctuations of the inflow velocity at the tidal (period 12 hours) and subinertial (period 10 days) frequencies. Tidal fluctuations produce only minor effects on the buoyant plume compared to the case of constant inflow, while subinertial fluctuations substantially modify the anticyclonic bulge. A partially detached anticyclonic plume forms when discharge subsides after reaching its peak value. Such a plume has maximum offshore extension some distance downstream of the mouth with the lightest water separated from the coast. A secondary bulge forms during the low runoff interval. When high discharge resumes, this secondary bulge is shifted offshore and enhanced for some time. An individual high-discharge event is next considered, where both the net transport of the inflow and the absolute value of its density anomaly increase and then return to their initial (background) values over 5 and 10 day time intervals. This event also generates a partially detached plume (especially with the 10 day duration). In this case, the lightest water occupies the downstream part of the bulge and is separated not only from the coast but also from the mouth. The effect of variable discharge is more dramatic with a uniform downstream current of 0.1 m s(-1). Under such conditions, constant buoyant discharge does not form a well-pronounced anticyclonic bulge. In contrast, variable discharge produces an almost circular anticyclone during the high-runoff interval. As runoff decreases, this anticyclone separates from the source and either continues to propagate downstream as an individual eddy or is modified by the next cycle of increasing discharge. Observational evidence for both the partially detached bulge near the mouth and the anticyclone propagating downstream from its source is presented in this study. One feature was observed at the mouth of the Columbia River estuary; the second feature was observed off the southern New Jersey coast similar to 150 km south of its source, the Hudson estuary. [References: 30]
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机译：使用原始方程数值模型（SPEM5）研究了浮力排放变化对沿海浮力驱动流动力学的影响。首先，引入可变排放量，作为潮汐（周期12小时）和亚惯性（周期10天）频率下流入速度的谐波波动。与持续流入的情况相比，潮汐波动对浮力羽流只产生很小的影响，而惯性波动则基本上改变了反气旋凸起。当排放量在达到峰值后消退时，会形成部分分离的反气旋羽流。这样的羽流具有最大的离岸延伸量，距嘴下游一定距离，且最轻的水与海岸分开。在低径流间隔期间形成次级凸起。当高流量恢复时，该次级凸起将移至海上并增强一段时间。接下来考虑一个单独的高流量事件，流入的净输运量及其密度异常的绝对值都会增加，然后在5天和10天的时间间隔内返回到其初始（背景）值。此事件还会生成部分分离的羽状流（尤其是持续10天的时间）。在这种情况下，最轻的水占据了凸起的下游部分，不仅与海岸分开，而且与嘴角分开。均匀下游电流为0.1 m s（-1）时，可变放电的影响更为显着。在这种情况下，持续的浮力排放不会形成发音充分的反气旋凸起。相反，可变排放在高径流间隔期间产生几乎圆形的反旋风器。随着径流的减少，该反旋风分离器与水源分离，或者继续作为单个涡流向下游传播，或者被下一个增加排放的循环所修饰。这项研究提供了嘴附近部分脱离的隆起和从其来源向下游传播的反气旋的观测证据。在哥伦比亚河河口处观察到一个特征。第二个特征是在新泽西州南部海岸附近观察到的，类似于其源头哈德逊河口以南150公里。 [参考：30]
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