The possible linkage of ENSO and IOD to JJAS rainfall variability over Ethiopia

The possible linkage of ENSO and IOD to JJAS rainfall variability over Ethiopia | 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 possible linkage of ENSO and IOD to JJAS rainfall variability over Ethiopia Habtam Jenberu Wassie, Tan Guirong This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8493289/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 Rainfall variability in Ethiopia is strongly influenced by large-scale sea surface temperature (SST) anomalies, notably the El Niño–Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD). This study examines June–September (JJAS) rainfall from 1991 to 2020 using multiple datasets and statistical methods, including t-tests, empirical orthogonal functions (EOF), composite analysis, correlation, and linear regression. The first EOF captures 64.4% of total rainfall variance and shows contrasting variability between northwest and southeast regions, effectively representing interannual JJAS rainfall patterns. Circulation analyses reveal that above-average rainfall is associated with lower pressure systems, enhanced convection, anomalous convergent flows, and positive water flux anomalies, while below-average rainfall corresponds to opposite conditions. ENSO shows a significant correlation with JJAS rainfall (r = − 0.66), while IOD exhibits a weaker but regionally relevant influence (r = 0.2), particularly in eastern Ethiopia. Warm SST anomalies in the central equatorial Pacific (El Niño) induce high pressure, positive outgoing long wave radiation, and subsidence over Ethiopia, reducing rainfall, whereas La Niña conditions enhance rainfall. IOD phases modulate low-level convergence and divergence patterns, further influencing regional precipitation. These results highlight the complex interplay between ENSO, IOD, and tropical circulation in shaping Ethiopia’s main rainy season, providing critical insights for planning, mitigation, and climate adaptation strategies. JJAS Rainfall ENSO IOD tropical circulation patterns Ethiopia Full Text Additional Declarations No competing interests reported. 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. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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-8493289","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":570401456,"identity":"e46adc32-8773-4e81-92a6-712970006779","order_by":0,"name":"Habtam Jenberu 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Ethiopia","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"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":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"JJAS Rainfall, ENSO, IOD, tropical circulation patterns, Ethiopia","lastPublishedDoi":"10.21203/rs.3.rs-8493289/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8493289/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eRainfall variability in Ethiopia is strongly influenced by large-scale sea surface temperature (SST) anomalies, notably the El Ni\u0026ntilde;o\u0026ndash;Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD). This study examines June\u0026ndash;September (JJAS) rainfall from 1991 to 2020 using multiple datasets and statistical methods, including t-tests, empirical orthogonal functions (EOF), composite analysis, correlation, and linear regression. The first EOF captures 64.4% of total rainfall variance and shows contrasting variability between northwest and southeast regions, effectively representing interannual JJAS rainfall patterns. Circulation analyses reveal that above-average rainfall is associated with lower pressure systems, enhanced convection, anomalous convergent flows, and positive water flux anomalies, while below-average rainfall corresponds to opposite conditions. ENSO shows a significant correlation with JJAS rainfall (r = \u0026minus;\u0026thinsp;0.66), while IOD exhibits a weaker but regionally relevant influence (r\u0026thinsp;=\u0026thinsp;0.2), particularly in eastern Ethiopia. Warm SST anomalies in the central equatorial Pacific (El Ni\u0026ntilde;o) induce high pressure, positive outgoing long wave radiation, and subsidence over Ethiopia, reducing rainfall, whereas La Ni\u0026ntilde;a conditions enhance rainfall. IOD phases modulate low-level convergence and divergence patterns, further influencing regional precipitation. These results highlight the complex interplay between ENSO, IOD, and tropical circulation in shaping Ethiopia\u0026rsquo;s main rainy season, providing critical insights for planning, mitigation, and climate adaptation strategies.\u003c/p\u003e","manuscriptTitle":"The possible linkage of ENSO and IOD to JJAS rainfall variability over Ethiopia","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-01-07 16:06:51","doi":"10.21203/rs.3.rs-8493289/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"efcbb0d9-366c-45b5-b958-b6e79b552815","owner":[],"postedDate":"January 7th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-01-27T20:38:56+00:00","versionOfRecord":[],"versionCreatedAt":"2026-01-07 16:06:51","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8493289","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8493289","identity":"rs-8493289","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}