Upwelling in coastal embayments is important to a variety of physical and biological processes. Despite their ubiquity, circulation patterns in small bays (width and length scales ≤ 20 km) in eastern boundary current upwelling systems are relatively understudied compared to their larger counterparts. In this study, we apply a conditional averaging technique to investigate upwelling- and downwelling-driven circulation in a small coastal embayment located in Central California (San Luis Obispo Bay). We also investigate intraseasonal differences in the current patterns. Conditional averaging reveals distinct intraseasonal differences and features that are obscured by traditional seasonal averages when examining the upwelling jet separation and onshore advection, horizontal divergence patterns, and particle trajectories. We show that the upwelling circulation and resulting upwelling jet separation and onshore advection reinforce a convergent upwelling shadow front at this site, with important ecological ramifications. While tuned specifically for San Luis Obispo Bay, these findings can be used as a baseline for similar small upwelling bays, highlight the importance of conditional averages (versus traditional temporal averages), and underline the importance of coastal upwelling seasonality beyond the common bimodal upwelling and non-upwelling description.

沿海海湾的上升流对各种物理和生物过程都很重要。尽管它们无处不在，但与较大的对应物相比，东部边界流上升流系统中小海湾（宽度和长度尺度≤ 20 公里）的环流模式研究相对较少。在这项研究中，我们应用条件平均技术来调查位于加利福尼亚中部（圣路易斯奥比斯波湾）的小型沿海海湾中的上升流和下降流驱动的环流。我们还调查了当前模式的季节性差异。在检查上升流急流分离和陆上平流、水平发散模式和粒子轨迹时，条件平均揭示了明显的季节内差异和特征，这些差异和特征被传统的季节性平均值所掩盖。我们表明，上升流环流和由此产生的上升流急流分离和陆上平流加强了该地点的汇聚上升流阴影锋，具有重要的生态后果。虽然专门针对圣路易斯奥比斯波湾进行了调整，但这些发现可用作类似小型上升流海湾的基线，突出了条件平均值（相对于传统时间平均值）的重要性，并强调了沿海上升流季节性的重要性，超出了常见的双峰上升流和非上升流描述。