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标题：A Numerical Study of the Global Formation of Tropical Cyclones
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作者：The‐Anh Vu ; Chanh Kieu ; Daniel Chavas 等
期刊名称：Journal of Advances in Modeling Earth Systems
电子版ISSN：1942-2466
出版年度：2021
卷号：13
期号：1
页码：e2020MS002207
DOI：10.1029/2020MS002207
出版社：John Wiley & Sons, Ltd.
摘要：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. Plain Language Abstract Understanding the mechanisms behind the upper bound on the global tropical cyclone (TC) number is important yet still elusive. Using TC simulations on an aquaplanet tropical channel, this study shows that the tropical atmosphere possesses a maximum capacity in producing TCs globally, regardless of how ideal the environmental conditions are. In particular, global TC formation does not occur throughout the year but in a series of episodes with a frequency of about 2 weeks, with ∼ 8–10 TCs per episode. Examination of the TC genesis index shows that midlevel moisture content and 850‐hPa absolute vorticity associated with the ITCZ instability are key factors governing the episodic global TC formation.
关键词：tropical cyclone formation;global tropical cyclone frequency;tropical cyclone simulation;global cyclogenesis