Revealing the relationship between ENSO and the annual cycle of the East Asia and western Pacific monsoon using a low-level circulation weather-type calendar

Revealing the relationship between ENSO and the annual cycle of the East Asia and western Pacific monsoon using a low-level circulation weather-type calendar | 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 Revealing the relationship between ENSO and the annual cycle of the East Asia and western Pacific monsoon using a low-level circulation weather-type calendar Yin-Min Cho, Mong-Ming Lu, Chung-Hsiung Sui, Jian-Hua Qian This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9133845/v1 This work is licensed under a CC BY 4.0 License Status: Under Revision Version 1 posted 9 You are reading this latest preprint version Abstract This paper proposes a novel approach to identifying the annual cycle and variability of the East Asia and western Pacific (EA-WP) monsoon. A low-level circulation weather type (WT) calendar is constructed based on nine WTs obtained from K-means cluster analysis for 46 years (1979–2024) of daily 850-hPa wind data. The WT daily occurrence frequency reveals climatological features of the monsoon annual cycle and seasonal progression. The WT-based summer and winter monsoon indices well represent key monsoon characteristics. A strong East Asian summer monsoon (EASM) corresponds to more frequent occurrences of WT featuring low-level anticyclonic circulation over the western North Pacific, while a strong East Asian winter monsoon (EAWM) corresponds to more frequent occurrences of WTs characterized by low-level northerly winds over the South China Sea and the Philippine Sea. The variability of EASM and EAWM is synchronized during the developing phase of ENSO events. Strong (weak) EA-WP monsoon years are marked by strong (weak) EASM followed by strong (weak) EAWM, whereas no clear relationship is found between EASM and its preceding EAWM. Approximately, 86% (76%) of the strong (weak) EA-WP monsoon years are associated with La Niña (El Niño) winters. The period from mid-July to late-August is identified as a critical window for the synchronization of monsoon and ENSO. Observational evidence suggests that strong and weak air-sea coupling represent two distinct states of EA-WP monsoon years. Under strong air-sea coupling, monsoon variability is significantly enhanced, with EA-WP monsoon and ENSO functioning as two interconnected components of a single coupled system. Full Text Additional Declarations No competing interests reported. Supplementary Files ChoLuSuiQian2026TAOsupplementaryinformation.docx Cite Share Download PDF Status: Under Revision Version 1 posted Editorial decision: Revision requested 16 Apr, 2026 Reviews received at journal 15 Apr, 2026 Reviews received at journal 11 Apr, 2026 Reviewers agreed at journal 19 Mar, 2026 Reviewers agreed at journal 18 Mar, 2026 Reviewers invited by journal 18 Mar, 2026 Editor assigned by journal 17 Mar, 2026 Submission checks completed at journal 17 Mar, 2026 First submitted to journal 16 Mar, 2026 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-9133845","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":607994528,"identity":"d6982550-23f7-4a96-9b20-01995e456670","order_by":0,"name":"Yin-Min Cho","email":"","orcid":"","institution":"National Central University","correspondingAuthor":false,"prefix":"","firstName":"Yin-Min","middleName":"","lastName":"Cho","suffix":""},{"id":607994529,"identity":"483d1c4a-c065-4312-9726-6c35ad1e1f66","order_by":1,"name":"Mong-Ming Lu","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA1klEQVRIiWNgGAWjYNACAwYGPgbmA0CWhAzxWtgY2BJAWniIt4iNgccARBPWotvee/jVjYI7dm0SOZ9f3aix4GFgP3x0Az4tZmfOpVnnGDxLbpPI3WadcwzoMJ60tBt4tdzIMTPOMTiczAbUYpzDBtQiwWNGrJacZ8Y5/4jTYvwYqMUOqIX5cW4bMVrOnDFjBmpJYON5Zsac2yfBw0bQL8d7jD/n/Dlsz8+e/Phzzrc6OX72w8fwagECNgkgkdgAZQAjiDBg/gAk7GGMUTAKRsEoGAUYAABk9kVqKYMLpwAAAABJRU5ErkJggg==","orcid":"","institution":"National Taiwan University","correspondingAuthor":true,"prefix":"","firstName":"Mong-Ming","middleName":"","lastName":"Lu","suffix":""},{"id":607994530,"identity":"0fa2f301-6a51-4dab-b95c-7e429153a96a","order_by":2,"name":"Chung-Hsiung Sui","email":"","orcid":"","institution":"National Taiwan University","correspondingAuthor":false,"prefix":"","firstName":"Chung-Hsiung","middleName":"","lastName":"Sui","suffix":""},{"id":607994531,"identity":"b2c67245-2139-4b36-bc08-9941389385d5","order_by":3,"name":"Jian-Hua Qian","email":"","orcid":"","institution":"Savannah River National Laboratory","correspondingAuthor":false,"prefix":"","firstName":"Jian-Hua","middleName":"","lastName":"Qian","suffix":""}],"badges":[],"createdAt":"2026-03-16 06:39:38","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9133845/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9133845/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":105050949,"identity":"607e9d32-ccf2-4038-8a7c-c82d2e8bd54f","added_by":"auto","created_at":"2026-03-20 10:17:01","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2346815,"visible":true,"origin":"","legend":"","description":"","filename":"ChoLuSuiQian2026TAOmanuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9133845/v1_covered_b839e51f-1480-4b5a-9c6e-cb224d2e325f.pdf"},{"id":105050948,"identity":"9ef52ff2-0ed5-4f91-a7ab-b3e446326127","added_by":"auto","created_at":"2026-03-20 10:16:52","extension":"docx","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":8450223,"visible":true,"origin":"","legend":"","description":"","filename":"ChoLuSuiQian2026TAOsupplementaryinformation.docx","url":"https://assets-eu.researchsquare.com/files/rs-9133845/v1/f9f55a3932f770d7692cd5bd.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Revealing the relationship between ENSO and the annual cycle of the East Asia and western Pacific monsoon using a low-level circulation weather-type calendar","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":true,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":true,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"terrestrial-atmospheric-and-oceanic-sciences","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"taoj","sideBox":"Learn more about [Terrestrial, Atmospheric and Oceanic Sciences](https://link.springer.com/journal/44195)","snPcode":"44195","submissionUrl":"https://submission.springernature.com/new-submission/44195/3","title":"Terrestrial, Atmospheric and Oceanic Sciences","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Open","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-9133845/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9133845/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis paper proposes a novel approach to identifying the annual cycle and variability of the East Asia and western Pacific (EA-WP) monsoon. A low-level circulation weather type (WT) calendar is constructed based on nine WTs obtained from K-means cluster analysis for 46 years (1979\u0026ndash;2024) of daily 850-hPa wind data. The WT daily occurrence frequency reveals climatological features of the monsoon annual cycle and seasonal progression. The WT-based summer and winter monsoon indices well represent key monsoon characteristics. A strong East Asian summer monsoon (EASM) corresponds to more frequent occurrences of WT featuring low-level anticyclonic circulation over the western North Pacific, while a strong East Asian winter monsoon (EAWM) corresponds to more frequent occurrences of WTs characterized by low-level northerly winds over the South China Sea and the Philippine Sea. The variability of EASM and EAWM is synchronized during the developing phase of ENSO events. Strong (weak) EA-WP monsoon years are marked by strong (weak) EASM followed by strong (weak) EAWM, whereas no clear relationship is found between EASM and its preceding EAWM. Approximately, 86% (76%) of the strong (weak) EA-WP monsoon years are associated with La Ni\u0026ntilde;a (El Ni\u0026ntilde;o) winters. The period from mid-July to late-August is identified as a critical window for the synchronization of monsoon and ENSO. Observational evidence suggests that strong and weak air-sea coupling represent two distinct states of EA-WP monsoon years. Under strong air-sea coupling, monsoon variability is significantly enhanced, with EA-WP monsoon and ENSO functioning as two interconnected components of a single coupled system.\u003c/p\u003e","manuscriptTitle":"Revealing the relationship between ENSO and the annual cycle of the East Asia and western Pacific monsoon using a low-level circulation weather-type calendar","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-03-20 10:16:30","doi":"10.21203/rs.3.rs-9133845/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-04-16T04:44:11+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-04-16T00:21:07+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-04-11T18:28:58+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"176408593832125751496819865486796542187","date":"2026-03-20T02:32:19+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"175570198144286403752920565613516281452","date":"2026-03-18T05:20:11+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-03-18T04:51:53+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-03-17T06:51:44+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-03-17T06:51:27+00:00","index":"","fulltext":""},{"type":"submitted","content":"Terrestrial, Atmospheric and Oceanic Sciences","date":"2026-03-16T06:35:35+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"terrestrial-atmospheric-and-oceanic-sciences","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"taoj","sideBox":"Learn more about [Terrestrial, Atmospheric and Oceanic Sciences](https://link.springer.com/journal/44195)","snPcode":"44195","submissionUrl":"https://submission.springernature.com/new-submission/44195/3","title":"Terrestrial, Atmospheric and Oceanic Sciences","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Open","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"81503a55-6992-4dc2-a3a5-2add55758ac4","owner":[],"postedDate":"March 20th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"in-revision","subjectAreas":[],"tags":[],"updatedAt":"2026-04-16T04:53:32+00:00","versionOfRecord":[],"versionCreatedAt":"2026-03-20 10:16:30","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9133845","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9133845","identity":"rs-9133845","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}