Abstract Early detection of disturbances in the atmospheric column, its spatio-temporal behavior and evolution prior to tropical cyclogenesis over warm ocean surface is a challenging problem. High-resolution atmospheric models help to better understand the atmospheric dynamical conditions and instability mechanism triggered by intense air-sea interaction leading to the formation of tropical cyclogenesis. Present study performed a series of model-based sensitivity experiments to evaluate tropical cyclogenesis lead detection time for five cyclone cases with varying grid resolutions ranging between 27 km and 12 km in the north Indian Ocean. High-resolution Weather Research and Forecast (WRF) model examined the evolution of pre-cyclonic eddy vortices in the vertical atmospheric column associated with Aila, Thane, Mora, Ockhi, and the recent Vayu cyclones. Detection technique was based on Okubo-Weiss (OW) parameter that is very sensitive to varying grid resolutions. Study examined the sensitivity of pre-cyclogenesis lead detection time to WRF model grid resolutions. Significant findings from the study indicate a good skill in genesis prediction with approximately four days (~90 h) lead time in all cases irrespective of pre- and post-monsoon seasons and the domain size. First part of this study reveals characteristic difference in the eddy detection between pre- and post-monsoon cyclones and its lead detection time. The lead detection time using a grid resolution of 27 km resulted in a lag-time of nearly one day (~24 h) for pre-monsoon cyclogenesis as compared to the post-monsoon cases. Interestingly, the pre-cyclonic eddies are detected at higher atmospheric levels (450–650 hPa) for the pre-monsoon unlike post-monsoon developing cases in the lower tropospheric levels (800–950 hPa). Secondly, a 15 km grid resolution with OW technique would suffice early tropical cyclogenesis detection found optimum in context to lead detection time (~15 h) that better resolves the structure of pre-cyclonic eddies useful for advanced prediction.

中文翻译：

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北印度洋气旋形成检测提前期的最佳网格分辨率

摘要 在温暖海洋表面的热带气旋发生之前早期检测大气柱中的扰动、其时空行为和演化是一个具有挑战性的问题。高分辨率大气模型有助于更好地理解由导致热带气旋形成的强烈海气相互作用引发的大气动力学条件和不稳定机制。目前的研究进行了一系列基于模型的灵敏度实验，以评估热带气旋的先导探测时间，对北印度洋 27 公里至 12 公里范围内不同网格分辨率的五个气旋案例进行评估。高分辨率天气研究和预报 (WRF) 模型检查了与 Aila、Thane、Mora、Ockhi、和最近的 Vayu 旋风。检测技术基于对不同网格分辨率非常敏感的 Okubo-Weiss (OW) 参数。研究检查了气旋前先导检测时间对 WRF 模型网格分辨率的敏感性。该研究的重要发现表明，无论季风前后季节和域大小如何，在所有情况下都具有大约四天（约 90 小时）的提前期，具有良好的成因预测技巧。本研究的第一部分揭示了季风前和季风后气旋涡旋探测的特征差异及其超前探测时间。与季风后情况相比，使用 27 公里网格分辨率的超前检测时间导致季风前气旋发生近一天（~24 小时）的滞后时间。有趣的是，与在较低对流层水平（800-950 hPa）的季风后发展情况不同，季风前在较高大气水平（450-650 hPa）检测到气旋前涡旋。其次，使用 OW 技术的 15 公里网格分辨率将足以在上下文中找到最佳的早期热带气旋检测，以领先检测时间（~15 小时），从而更好地解析可用于高级预测的气旋前涡旋的结构。