Novel Monsoon Indices Based on Vector Projection and Directed Angle for Measuring East Asian Summer Monsoon

Novel Monsoon Indices Based on Vector Projection and Directed Angle for Measuring East Asian Summer Monsoon | 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 Research Article Novel Monsoon Indices Based on Vector Projection and Directed Angle for Measuring East Asian Summer Monsoon Yinan Yang, Jianping Li This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6132038/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 01 May, 2025 Read the published version in Climate Dynamics → Version 1 posted 5 You are reading this latest preprint version Abstract This study presents a novel framework within a unified monsoon coordinate system for quantifying variability of the East Asian Summer Monsoon (EASM) through integrating two new concepts: the monsoon vector projection (MVP), quantifying monsoon intensity and directed angle (DA), capturing monsoon directional variability. The newly introduced MVP and DA indices based on the framework show very significant correlations with summer precipitation in the middle-lower Yangtze River, much more surpassing previous EASM indices and can also capture the Meiyu-Changma-Baiu belt's spatial pattern more clearly and comprehensively. Strong EASM years are characterized by convergence, indicated by the MVP along the Meiyu front, coupled with anomalous cyclonic shear, reflected by the DA deflection, being associated with wetter conditions in the Meiyu belt and the westward extension and southward shift of the Western Pacific Subtropical High (WPSH), alongside drier conditions in northern China, which together manifest the north-south precipitation dipole pattern. In contrast, weak EASM years exhibit the opposite characteristics of strong EASM years. Moreover, this paper also proposes a creative conception—the Rossby wave ray flux (WRF), which can reflect the pathway of Rossby wave activity of the Indo-Asian-Pacific (IAP) teleconnection very well. The monsoon coordinate system can be extended to other monsoon domains and could provide valuable insights for better capturing variabilities of monsoons and understanding their relationships with other climate factors in the future. Meanwhile, the WRF may provide a new tool for diagnosing local activity and propagation direction of Rossby waves. East Asian Summer Monsoon index Monsoon vector projection Directed angle Monsoon coordinate system Rossby wave ray flux Full Text Supplementary Files SupplementaryMaterial.docx Cite Share Download PDF Status: Published Journal Publication published 01 May, 2025 Read the published version in Climate Dynamics → Version 1 posted Reviewers agreed at journal 31 Mar, 2025 Reviewers invited by journal 30 Mar, 2025 Editor assigned by journal 28 Mar, 2025 First submitted to journal 25 Mar, 2025 Editorial decision: Minor Revision 17 Mar, 2025 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. We do this by developing innovative software and high quality services for the global research community. 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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-6132038","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":436034620,"identity":"125886c8-ab04-4741-81cf-10daf43d418a","order_by":0,"name":"Yinan Yang","email":"","orcid":"","institution":"Ocean University of China","correspondingAuthor":false,"prefix":"","firstName":"Yinan","middleName":"","lastName":"Yang","suffix":""},{"id":436034621,"identity":"aedb6ec0-c371-42d9-a0e2-995c9915fa59","order_by":1,"name":"Jianping Li","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAoklEQVRIiWNgGAWjYBACPoYDjA8gzAQitbAxHGA2IFULA5sEiVoYzx6r+Nhmx8DPnmPA8HMHUbacS7s5sy2ZQbLnjQFj7xmitJwxu83bdoDB4EaOATNjG5FaikFa7EnSwgy2RYJ4LeeSJWecS+aROPOs4GAvMVr4Jc4e/PChzE6Ovz1544OfxGhhkIAEEg+IOECMBqA1PcSpGwWjYBSMghEMAH6nMPA/o1HAAAAAAElFTkSuQmCC","orcid":"https://orcid.org/0000-0003-0625-1575","institution":"Ocean University of China","correspondingAuthor":true,"prefix":"","firstName":"Jianping","middleName":"","lastName":"Li","suffix":""}],"badges":[],"createdAt":"2025-03-01 02:30:45","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6132038/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6132038/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s00382-025-07696-7","type":"published","date":"2025-05-01T15:57:46+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":81988023,"identity":"648dd804-67de-4de9-8660-092d444f8fdc","added_by":"auto","created_at":"2025-05-05 16:07:26","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2341197,"visible":true,"origin":"","legend":"","description":"","filename":"RevisedManuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6132038/v1_covered_3cb90a4c-8df6-4b21-bda2-2ad46456843e.pdf"},{"id":79636607,"identity":"f75f1322-15ff-4bdc-8670-f2fc300737c3","added_by":"auto","created_at":"2025-04-01 04:49:44","extension":"docx","order_by":15,"title":"","display":"","copyAsset":false,"role":"supplement","size":810989,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementaryMaterial.docx","url":"https://assets-eu.researchsquare.com/files/rs-6132038/v1/56d16e699f3526987384bebe.docx"}],"financialInterests":"","formattedTitle":"Novel Monsoon Indices Based on Vector Projection and Directed Angle for Measuring East Asian Summer Monsoon","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":true,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":true,"isPdf":true,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"climate-dynamics","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"cldy","sideBox":"Learn more about [Climate Dynamics](https://www.springer.com/journal/382)","snPcode":"382","submissionUrl":"https://submission.nature.com/new-submission/382/3","title":"Climate Dynamics","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"East Asian Summer Monsoon index, Monsoon vector projection, Directed angle, Monsoon coordinate system, Rossby wave ray flux","lastPublishedDoi":"10.21203/rs.3.rs-6132038/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6132038/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis study presents a novel framework within a unified monsoon coordinate system for quantifying variability of the East Asian Summer Monsoon (EASM) through integrating two new concepts: the monsoon vector projection (MVP), quantifying monsoon intensity and directed angle (DA), capturing monsoon directional variability. The newly introduced MVP and DA indices based on the framework show very significant correlations with summer precipitation in the middle-lower Yangtze River, much more surpassing previous EASM indices and can also capture the Meiyu-Changma-Baiu belt's spatial pattern more clearly and comprehensively. Strong EASM years are characterized by convergence, indicated by the MVP along the Meiyu front, coupled with anomalous cyclonic shear, reflected by the DA deflection, being associated with wetter conditions in the Meiyu belt and the westward extension and southward shift of the Western Pacific Subtropical High (WPSH), alongside drier conditions in northern China, which together manifest the north-south precipitation dipole pattern. In contrast, weak EASM years exhibit the opposite characteristics of strong EASM years. Moreover, this paper also proposes a creative conception\u0026mdash;the Rossby wave ray flux (WRF), which can reflect the pathway of Rossby wave activity of the Indo-Asian-Pacific (IAP) teleconnection very well. The monsoon coordinate system can be extended to other monsoon domains and could provide valuable insights for better capturing variabilities of monsoons and understanding their relationships with other climate factors in the future. 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