Abstract We investigated the performance of a tidally and subtidally forced open boundary condition (TST-OBC) on the estuarine–shelf circulation in a limited-area, down-scaling numerical modeling system for the northern South China Sea. We forced the modeling system with amplified tidal forces and subtidal forcing of spatiotemporally variable wind and river discharge. TST-OBC numerically and physically accommodates the circulation driven by the regional tides, subtidal forces, external forcing from its upscale solution, and internally generated disturbances. The advantages of TST-OBC are the separation of fast tidal and slow subtidal modes, active and dual-wave transmitting schemes, consistent treatment of barotropic and baroclinic circulation, and thermodynamic variables, which enable the model to capture observed circulation characteristics. The results differ from the results obtained using the Flather-type OBC, which over-restores internal to external solutions with a notable accumulation of spurious disturbances along the open boundaries. Disturbances with both tidal and subtidal signals that arrive at the open boundaries are well-treated by adopting TST-OBC, although it is currently feasible for the one-way downscaling applications.

中文翻译：

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使用复合潮汐和潮下开放边界条件的河口-陆架环流模拟研究

摘要 我们研究了潮汐和潮下强迫开放边界条件 (TST-OBC) 在南海北部有限区域、按比例缩小的数值模拟系统中对河口-陆架环流的性能。我们用放大的潮汐力和时空变化的风和河流流量的潮下强迫来强制建模系统。TST-OBC 在数值和物理上适应区域潮汐驱动的环流、潮下力、来自其高档解的外力以及内部产生的扰动。TST-OBC 的优点是快潮下模式和慢潮下模式的分离、主动和双波传输方案、正压和斜压环流的一致处理以及热力学变量，使模型能够捕获观测到的环流特征。结果与使用 Flather 型 OBC 获得的结果不同，后者过度恢复内部到外部解决方案，并沿开放边界显着积累虚假扰动。采用 TST-OBC 可以很好地处理到达开放边界的潮汐和潮下信号的干扰，尽管它目前对于单向降尺度应用是可行的。