Coastal upwelling along the southwestern coast of Sumatra is a seasonal upwelling that occurs in areas of high sea surface temperature and abundant precipitation at the southeastern edge of the Indian Ocean warm pool. Based on observations from two Argo floats that drifted and stayed around Sumatra, we investigated ocean temperature and salinity variations during several coastal upwelling events observed in 2013–2017. The Argo floats observed the vertical structure of temperature and salinity every 10 days within 100 km from the southwestern coast of Sumatra. The observation data show intraseasonal‐scale subsurface temperature cooling events with significant upward displacements of the thermocline and high‐salinity water, led by anomalous local southesterly winds and equatorial easterly winds. During the coastal upwelling events, salinity stratification and a thick barrier layer related to local precipitation were also observed. Surface mixed layer temperature cooling were relatively small in contrast to the significant subsurface anomalies. It was found that during the coastal upwelling events, subsurface cold‐water upwelling signals did not necessarily reach the mixed layer when salinity stratification and a thick barrier layer were present. The implications of these observational results for understanding the local atmosphere ocean interaction, and hence the occurrence of the Indian Ocean Dipole, are discussed.

中文翻译：

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苏门答腊西南海岸沿岸上升流事件，盐度分层和障碍层

苏门答腊西南海岸的沿海上升流是季节性上升流，发生在印度洋暖池东南缘海平面温度高和降水丰富的地区。基于对两个在苏门答腊岛漂流并停留的Argo浮标的观察，我们调查了2013-2017年观测到的几个沿海上升事件期间的海洋温度和盐度变化。Argo浮标在距苏门答腊西南海岸100公里以内每10天观察到温度和盐度的垂直结构。观测数据表明，季节内尺度下的地表温度降温事件伴有温跃层和高盐度水的明显向上位移，这是由异常的南风和赤道东风引起的。在沿海上升事件中，还观察到盐分分层和与局部降水有关的厚阻挡层。与明显的地下异常相比，表面混合层温度冷却相对较小。发现在沿海上升事件中，当存在盐分分层和厚阻隔层时，地下冷水上升信号不一定到达混合层。讨论了这些观测结果对理解当地大气海洋相互作用以及印度洋偶极子的发生的意义。当存在盐分分层和厚阻挡层时，地下冷水上升流信号不一定到达混合层。讨论了这些观测结果对理解当地大气海洋相互作用以及印度洋偶极子的发生的意义。当存在盐分分层和厚阻挡层时，地下冷水上升流信号不一定到达混合层。讨论了这些观测结果对理解当地大气海洋相互作用以及印度洋偶极子的发生的意义。