发表机构
Max Planck Institute for Meteorology; Weizmann Institute of Science（马克斯·普朗克气象研究所; 魏茨曼科学研究所）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究从风暴中心视角，利用板式海洋模型和ERA5数据，揭示中纬度近惯性波生成效率由风暴强度、传播速度和纬度决定，极端事件中冷区增强动量传递。
AI 中文摘要
由温带气旋生成的近惯性波（NIWs）是将大气能量传递到海洋的主要途径，然而在单个风暴层面上，决定这种能量传递效率的因素仍然知之甚少。本文利用由ERA5再分析数据驱动的板式海洋模型，并在风暴相对坐标下进行分析，研究了三个时间尺度上的NIW生成：从单个风暴的瞬时结构，到其生命周期的演变，再到风暴间的变率。瞬时风暴结构揭示，风应力的空间布局和风暴的传播提供了所需的时间演变和旋转，从而在风暴路径的右侧激发风做功的局部最大值，这与热带气旋的情况类似。追踪风暴的生命周期进一步揭示，风做功在气旋生成后一天达到峰值，比风暴达到最大强度约早一天。这种偏移的产生是因为风暴在增强过程中平移速度减慢，减少了传播引起的风应力趋势，同时向极地的传播增加了科里奥利参数，并降低了风向与近惯性流之间的对齐程度。由于这种时间滞后，气候学上高NIW强迫的区域位于北太平洋风暴路径最大值的上游。最后，通过检查风暴间的变率，我们表明风暴强度、传播速度和纬度解释了NIW生成的大部分变率，但不包括极端事件。聚焦极端事件，我们发现最强的NIW生成风暴具有更冷的冷区，这使海洋边界层不稳定，并增强向海洋表面的向下动量传递。
英文摘要
Near-inertial waves (NIWs) generated by extratropical storms provide a major pathway for transferring atmospheric energy into the ocean, yet what determines the efficiency of this energy transfer at the level of individual storms remains poorly understood. Here, using a slab ocean model forced by ERA5 reanalysis and analyzed in storm-relative coordinates, we investigate NIW generation across three temporal scales: from the instantaneous structure of individual storms, through their life cycle, to variability across storms. Instantaneous storm structure reveals that the spatial layout of wind stress and storm propagation provides the required time evolution and rotation to excite a localized maximum in wind work on the right side of storm tracks, much like tropical cyclones do. Following storms through their life cycle further reveals that wind work peaks one day after cyclone genesis, about one day before storms reach their maximum intensity. This offset arises because storm translation slows during intensification, reducing the propagation-induced wind-stress tendency, while concurrent poleward propagation increases the Coriolis parameter and reduces the alignment between winds and near-inertial currents. Due to the temporal lag, regions of climatologically high NIW forcing are located upstream of the North Pacific storm-track maximum. Finally, examining variability across storms, we show that storm intensity, propagation speed, and latitude explain most of the variability in NIW generation, but not in extreme events. Focusing on extreme events, we find that the strongest NIW-generating storms feature colder cold sectors, which destabilize the marine boundary layer and enhance downward momentum transfer to the ocean surface.
