This study explores the influence of Stokes drift and the thermal effects on the upper ocean bias which occurs in the summer with overestimated sea surface temperature (SST) and shallower mixed layer depth (MLD) using Mellor-Yamada turbulence closure scheme. The upper ocean thermal structures through Princeton ocean model are examined by experiments in the cases of idealized forcing and real observational situation. The results suggest that Stokes drift can generally enhance turbulence kinetic energy and deepen MLD either in summer or in winter. This effect will improve the simulation results in summer, but it will lead to much deeper MLD in winter compared to observational data. It is found that MLD can be correctly simulated by combining Stokes drift and the thermal effects of the cool skin layer and diurnal warm layer on the upper mixing layer. In the case of high shortwave radiation and weak wind speed, which usually occurs in summer, the heat absorbed from sun is blocked in the warm layer and prevented from being transferred downwards. As a result, the thermal effects in summer nearly has no influence on dynamic effect of Stokes drift that leads to deepening MLD. However, when the stratification is weak in winter, the thermal effects will counteract the dynamic effect of Stokes drift through enhancing the strength of stratification and suppress mixing impact. Therefore, the dynamic and thermal effects should be considered simultaneously in order to correctly simulate upper ocean thermal structures in both summer and winter.

中文翻译：

---

斯托克斯漂移和海洋混合层热效应的数值研究

这项研究利用梅洛尔-山田湍流封闭方案探索了斯托克斯漂移和热效应对夏季发生的高洋偏向的影响，高估了海面温度（SST），混合层深度较浅（MLD）。在理想强迫和真实观测情况下，通过实验检查了普林斯顿海洋模型的上部海洋热结构。结果表明，斯托克斯漂移通常可以在夏季或冬季增强湍流动能并加深MLD。这种效果将改善夏季的模拟结果，但与观测数据相比，它将导致冬季的MLD更深。发现通过结合斯托克斯漂移和上部混合层上的冷皮层和昼间暖层的热效应可以正确模拟MLD。在短波辐射较高且风速较弱的情况下（通常发生在夏季），从太阳吸收的热量被阻挡在温暖的层中，并被阻止向下传播。结果，夏季的热效应几乎不会影响导致MLD加深的斯托克斯漂移的动力效应。然而，当冬季分层较弱时，热效应将通过增强分层强度并抑制混合冲击来抵消斯托克斯漂移的动力效应。因此，应同时考虑动力和热效应，以正确模拟夏季和冬季的上层海洋热结构。从太阳吸收的热量被阻挡在温暖的层中，并被阻止向下传播。结果，夏季的热效应几乎不会影响导致MLD加深的斯托克斯漂移的动力效应。然而，当冬季分层较弱时，热效应将通过增强分层强度并抑制混合冲击来抵消斯托克斯漂移的动力效应。因此，应同时考虑动力和热效应，以正确模拟夏季和冬季的上层海洋热结构。从太阳吸收的热量被阻挡在温暖的层中，并被阻止向下传播。结果，夏季的热效应几乎不会影响导致MLD加深的斯托克斯漂移的动力效应。然而，当冬季分层较弱时，热效应将通过增强分层强度并抑制混合冲击来抵消斯托克斯漂移的动力效应。因此，应同时考虑动力和热效应，以正确模拟夏季和冬季的上层海洋热结构。热效应将通过增强分层强度并抑制混合冲击来抵消斯托克斯漂移的动态影响。因此，应同时考虑动力和热效应，以正确模拟夏季和冬季的上层海洋热结构。热效应将通过增强分层强度并抑制混合冲击来抵消斯托克斯漂移的动态影响。因此，应同时考虑动力和热效应，以正确模拟夏季和冬季的上层海洋热结构。