The Saharan Oscillation Index (1950–2024): Phase Structure, Regime Shifts, and Global Teleconnections

The Saharan Oscillation Index (1950–2024): Phase Structure, Regime Shifts, and Global Teleconnections | 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 The Saharan Oscillation Index (1950–2024): Phase Structure, Regime Shifts, and Global Teleconnections Younes TEBBAAI, Kenza KHOMSI, Mohamed KHALIS This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8832891/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 9 You are reading this latest preprint version Abstract The Saharan Oscillation Index (SaOI) quantifies the pressure gradient between the Azores High and the Niamey Saharan low, capturing atmospheric variability that influences climate across the Euro-Atlantic-African sector. Despite its relevance to regional hydroclimate, dust transport, and air quality, the temporal structure of SaOI phases and their teleconnections with global climate modes remain poorly characterized. Here, we analyze 75 years (1950–2024) of SaOI variability using phase classification and seasonal lag-correlation analysis with fourteen large-scale climate indicators (LSCIs). We identify three distinct epochs: balanced phase distribution (1950–1965), sustained variability (1965–1990), and a pronounced shift toward positive-neutral dominance post-1990, with markedly reduced negative phase frequency after 2010. The SaOI exhibits moderate but statistically significant correlations with the North Atlantic Oscillation Index (NAOI; r = 0.42), Arctic Oscillation Index (AOI; r = 0.42), and Oceanic Niño Index (ONI; r = -0.44), with seasonal correlations revealing lagged teleconnections extending from late winter through summer. Positive phases are characterized by intensified pressure gradients that strengthen trade winds, suppress precipitation, and enhance dust mobilization, while negative phases promote moisture advection and convective activity. The apparent regime shift post-1990 raises critical questions about potential non-stationarity driven by anthropogenic forcing or natural multidecadal variability. These findings establish the SaOI as a key diagnostic tool linking regional Saharan dynamics to global climate variability, with applications for early warning systems addressing drought, air pollution, and heat-related risks across northwestern Africa and the Mediterranean. Saharan Oscillation Index atmospheric circulation climate teleconnections North Atlantic Oscillation phase classification regime shift Full Text Additional Declarations No competing interests reported. Supplementary Files SupplementaryMaterial.docx Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 23 Mar, 2026 Reviews received at journal 23 Mar, 2026 Reviewers agreed at journal 03 Mar, 2026 Reviews received at journal 01 Mar, 2026 Reviewers agreed at journal 16 Feb, 2026 Reviewers invited by journal 16 Feb, 2026 Editor assigned by journal 11 Feb, 2026 Submission checks completed at journal 11 Feb, 2026 First submitted to journal 09 Feb, 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-8832891","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":592854837,"identity":"d4ad206d-012f-44a0-824c-62c83da79a0b","order_by":0,"name":"Younes TEBBAAI","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA00lEQVRIiWNgGAWjYHACNmYgwcPPwMD4gEgNUC2SDQzMBiRpYTA4wMAmQJQOg/vNxx4X1NjJGN/ITmP88Ychmr+BkJZjbOnGM44l85jdyN32mLeNIXfGAYJaeMykediYQVq2GzM2MOQ2ENbC/02a5189j/GM3G2SQIflzifCFjZp3rbDPAYSudskeNgYcjcQ0iJ5LM3ceGbfcR6JM283G/O2SeRuJKSF7/DhZ48LvlXb87fnbnz4449N7jxCWhTQFEgQUA8E8g2E1YyCUTAKRsFIBwCn9UEKiVUKqwAAAABJRU5ErkJggg==","orcid":"","institution":"Mohammed VI Center for Research and Innovation","correspondingAuthor":true,"prefix":"","firstName":"Younes","middleName":"","lastName":"TEBBAAI","suffix":""},{"id":592854838,"identity":"82207a2a-ed13-4cde-9bf2-10abb34cfc01","order_by":1,"name":"Kenza KHOMSI","email":"","orcid":"","institution":"Mohammed VI International School of Public Health, Mohammed VI University of Sciences and Health","correspondingAuthor":false,"prefix":"","firstName":"Kenza","middleName":"","lastName":"KHOMSI","suffix":""},{"id":592854839,"identity":"cadc05c6-bd10-4d66-be95-c50867f10861","order_by":2,"name":"Mohamed KHALIS","email":"","orcid":"","institution":"Mohammed VI Center for Research and Innovation","correspondingAuthor":false,"prefix":"","firstName":"Mohamed","middleName":"","lastName":"KHALIS","suffix":""}],"badges":[],"createdAt":"2026-02-09 16:55:17","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8832891/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8832891/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":103226895,"identity":"cb850517-f765-442c-be69-edc3b3cb6b05","added_by":"auto","created_at":"2026-02-23 11:17:20","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":693191,"visible":true,"origin":"","legend":"","description":"","filename":"TheSaharanOscillationIndex19502024PhaseStructureRegimeShiftsandGlobalTeleconnections.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8832891/v1_covered_8a661ce0-fd5e-4f45-a8c2-8c4fdbfadafe.pdf"},{"id":103226891,"identity":"90322aa1-891c-4568-92f9-f6bcd89fdafe","added_by":"auto","created_at":"2026-02-23 11:17:03","extension":"docx","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":71024,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementaryMaterial.docx","url":"https://assets-eu.researchsquare.com/files/rs-8832891/v1/5e89f37923a0ac24ce76a1de.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"The Saharan Oscillation Index (1950–2024): Phase Structure, Regime Shifts, and Global Teleconnections","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":false,"isPdf":true,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"theoretical-and-applied-climatology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"taac","sideBox":"Learn more about [Theoretical and Applied Climatology](https://www.springer.com/journal/704)","snPcode":"704","submissionUrl":"https://submission.nature.com/new-submission/704/3","title":"Theoretical and Applied Climatology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Saharan Oscillation Index, atmospheric circulation, climate teleconnections, North Atlantic Oscillation, phase classification, regime shift","lastPublishedDoi":"10.21203/rs.3.rs-8832891/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8832891/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe Saharan Oscillation Index (SaOI) quantifies the pressure gradient between the Azores High and the Niamey Saharan low, capturing atmospheric variability that influences climate across the Euro-Atlantic-African sector. Despite its relevance to regional hydroclimate, dust transport, and air quality, the temporal structure of SaOI phases and their teleconnections with global climate modes remain poorly characterized. Here, we analyze 75 years (1950\u0026ndash;2024) of SaOI variability using phase classification and seasonal lag-correlation analysis with fourteen large-scale climate indicators (LSCIs). We identify three distinct epochs: balanced phase distribution (1950\u0026ndash;1965), sustained variability (1965\u0026ndash;1990), and a pronounced shift toward positive-neutral dominance post-1990, with markedly reduced negative phase frequency after 2010. 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