Intraseasonal variability (ISV) of the upper 500 m circulation in the southern Bay of Bengal (SBOB) is investigated by using mooring observations and analyzing model outputs. An enhanced ISV is found in the upper 500 m currents during summer 2016. In summer 2016, a boreal summer intraseasonal oscillation (BSISO) propagated northward in tropical Indian Ocean. The intraseasonal easterly anomaly associated with the BSISO forces the equatorial wave to propagate into SBOB, driving the ISV of the upper currents. However, the analysis shows that the enhancement of ISV may be more related to the oceanic instability. During summer 2016, the intensity of the southwest monsoon current (SMC) significantly increased with the position of the flow axis closer to the SBOB's eastern boundary. Energy analysis reveals that the SMC could strengthen the westward propagating Rossby wave through baroclinic and barotropic instability, which can lead to the enhanced ISV of the upper currents in SBOB.

中文翻译：

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2016 年夏季孟加拉湾南部上层季节内变异性增强

通过使用系泊观测和分析模型输出，研究了孟加拉湾南部 (SBOB) 上层 500 米环流的季节内变化 (ISV)。2016 年夏季，在上层 500 m 洋流中发现了增强的 ISV。 2016 年夏季，北半球夏季季内振荡 (BSISO) 在热带印度洋向北传播。与 BSISO 相关的季内东风异常迫使赤道波传播到 SBOB，驱动高流的 ISV。但分析表明，ISV的增强可能更多地与海洋不稳定性有关。2016年夏季，随着流轴位置靠近SBOB东部边界，西南季风流（SMC）强度显着增加。