This study examines the large‐scale factors that govern global tropical cyclone (TC) formation and an upper bound on the annual number of TCs. Using idealized simulations for an aquaplanet tropical channel, it is shown that the tropical atmosphere has a maximum capacity in generating TCs, even under ideal environmental conditions. Regardless of how favorable the tropical environment is, the total number of TCs generated in the tropical channel possesses a consistent cap across experiments. Analyses of daily TC genesis events reveal further that global TC formation is intermittent throughout the year in a series of episodes at a roughly 2‐week frequency, with a cap of 8–10 genesis events per day. Examination of different large‐scale environmental factors shows that 600‐hPa moisture content, 850‐hPa absolute vorticity, and vertical wind shear are the most critical factors for this global episodic TC formation. Specifically, both the 850‐hPa absolute vorticity and the 600‐hPa moisture are relatively higher at the onset of TC formation episodes. Once TCs form and move to poleward, the total moisture content and the absolute vorticity in the main genesis region subside, thus reducing large‐scale instability and producing an unfavorable environment for TCs to form. It takes ∼2 weeks for the tropical atmosphere to remoisten and rebuild the large‐scale instability associated with the Intertropical Convergence Zone before a new TC formation episode can occur. These results offer new insight into the processes that control the upper bound on the global number of TCs in the range of 80–100 annually.

中文翻译：

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热带气旋全球形成的数值研究

这项研究探讨了控制全球热带气旋（TC）形成的大规模因素以及每年TC数量的上限。通过对滑水行星热带通道进行理想化模拟，结果表明，即使在理想的环境条件下，热带大气也具有产生TC的最大能力。无论热带环境多么有利，热带通道中产生的总TC数量在整个实验中都具有一致的上限。对每日TC发生事件的分析进一步揭示，全球TC的形成在一年中的一系列事件中是间歇性的，大约每2周一次，每天上限为8-10次。对各种大型环境因素的研究表明，水分含量为600hPa，绝对涡度为850hPa，垂直风切变是这种全球性偶发TC形成的最关键因素。具体来说，在TC形成事件开始时，850-hPa的绝对涡度和600-hPa的水分都相对较高。TC形成并向极地移动后，主成因区的总水分含量和绝对涡度就会消退，从而减少了大规模的不稳定性，并为TC形成提供了不利的环境。它需要 因此减少了大规模的不稳定，并为形成TC创造了不利的环境。它需要 因此减少了大规模的不稳定，并为形成TC创造了不利的环境。它需要〜 2周的热带氛围remoisten和重建一个新的TC形成发作可发生之前，热带辐合带相关的大规模的不稳定。这些结果为控制全球TC数量上限（每年80-100个）的过程提供了新见解。