Dual-Scale Controls of Vertical Eddy Diffusivity in Tropical Cyclone Rapid Intensification Forecasts

Dual-Scale Controls of Vertical Eddy Diffusivity in Tropical Cyclone Rapid Intensification Forecasts | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Dual-Scale Controls of Vertical Eddy Diffusivity in Tropical Cyclone Rapid Intensification Forecasts Xuesong Zhu, Xu Zhang, Bowen Zhao, Wei Huang, Hui Yu, Qijun Huang, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7052138/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract The escalating threat of rapidly intensifying Tropical Cyclones (TCs) to global coastal communities underscores the urgent need to advance TC intensity forecasting. While planetary boundary layer (PBL) processes regulate energy sources and sink essential for TC development, improving vertical eddy diffusivity ( K m ) parameterization has long been constrained by semi-empirical approaches. Within an unstructured mesh global model framework, we demonstrate that TC rapid intensification (RI) is fundamentally governed by two scaling parameters of K m : vertical extent ( h ) and peak magnitude ( α ), which are optimized through validation against previous observations. Mechanistically, h modulates vortex spin-up efficiency by controlling vertical diffusion and low-level moisture flux gradient, whereas α regulates boundary layer gradient imbalance during RI stage through downward mixing of tangential momentum. Implementation of the optimized K m parameterization reduces maximum wind speed forecasting error by 58.7% (or 4.5 m s–1) averaged over 72-hour leading time, attributing to the enhanced RI forecasting capability. These findings establish the first unified paradigm linking turbulent processes to RI physics, offering transformative potential for refining TC modeling. Earth and environmental sciences/Climate sciences/Atmospheric science/Atmospheric dynamics Scientific community and society/Social sciences/Climate change/Climate and Earth system modelling Tropical Cyclone rapid intensification planetary boundary layer scheme vertical eddy diffusivity turbulent and mixing process Full Text Additional Declarations There is NO Competing Interest. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7052138","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":483939386,"identity":"a8ea45dc-6c04-42cf-a5ea-b6e2c961153f","order_by":0,"name":"Xuesong 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While planetary boundary layer (PBL) processes regulate energy sources and sink essential for TC development, improving vertical eddy diffusivity (\u003cem\u003eK\u003c/em\u003e\u003csub\u003e\u003cem\u003em\u003c/em\u003e\u003c/sub\u003e) parameterization has long been constrained by semi-empirical approaches. Within an unstructured mesh global model framework, we demonstrate that TC rapid intensification (RI) is fundamentally governed by two scaling parameters of \u003cem\u003eK\u003c/em\u003e\u003csub\u003e\u003cem\u003em \u003c/em\u003e\u003c/sub\u003e: vertical extent (\u003cem\u003eh\u003c/em\u003e) and peak magnitude (\u003cem\u003eα\u003c/em\u003e), which are optimized through validation against previous observations. Mechanistically, \u003cem\u003eh\u003c/em\u003e modulates vortex spin-up efficiency by controlling vertical diffusion and low-level moisture flux gradient, whereas \u003cem\u003eα\u003c/em\u003e regulates boundary layer gradient imbalance during RI stage through downward mixing of tangential momentum. Implementation of the optimized \u003cem\u003eK\u003c/em\u003e\u003csub\u003e\u003cem\u003em \u003c/em\u003e\u003c/sub\u003eparameterization reduces maximum wind speed forecasting error by 58.7% (or 4.5 m s–1) averaged over 72-hour leading time, attributing to the enhanced RI forecasting capability. 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