High-latitude, low-altitude stratospheric aerosol injection reshapes West African monsoon rainfall and associated dynamics

High-latitude, low-altitude stratospheric aerosol injection reshapes West African monsoon rainfall and associated dynamics | 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 High-latitude, low-altitude stratospheric aerosol injection reshapes West African monsoon rainfall and associated dynamics Kwesi Twentwewa Quagraine, Kwesi Akumenyi Quagraine, Emmanuel Akalanyabah, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9315964/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 Stratospheric aerosol injection (SAI) is proposed as a near-term intervention to offset warming, yet its regional impacts remain uncertain. We assess the response of the West African Monsoon (WAM) to high-latitude, low-altitude SAI (HiLLA-SAI) using WACCM6 and UKESM1 simulations. Both models reproduce the seasonal cycle but exhibit systematic biases in rainfall magnitude and extremes. Under SAI, precipitation responses are spatially heterogeneous, with the largest anomalies in July–August. WACCM6 projects widespread wet biases extending inland from the Guinea Coast, whereas UKESM1 produces weaker and more heterogeneous responses, including drying over the Guinea Highlands and Nigeria. Both models show reduced wet spell persistence along the coast and increased dry spell duration over the Sahel. Dynamically, SAI reduces the meridional temperature gradient and shifts the African Easterly Jet southward, consistent with a reduced northward extent of the rain belt. However, responses differ markedly across models, indicating strong model dependence and heterogeneous responses of SAI to WAM conditions. Earth and environmental sciences/Climate sciences Earth and environmental sciences/Environmental sciences Stratospheric aerosol injection (SAI) West African Monsoon (WAM) precipitation extremes dry spell duration wet spell persistence climate model intercomparison HiLLA-SAI 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-9315964","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":627337610,"identity":"c3770a05-8598-4e68-a946-e3107d4eed22","order_by":0,"name":"Kwesi Twentwewa Quagraine","email":"","orcid":"","institution":"Texas A\u0026M University","correspondingAuthor":false,"prefix":"","firstName":"Kwesi","middleName":"Twentwewa","lastName":"Quagraine","suffix":""},{"id":627337612,"identity":"08f07a95-33c2-4e3e-a3a9-5619239b4eea","order_by":1,"name":"Kwesi Akumenyi Quagraine","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAuElEQVRIiWNgGAWjYBACCRCRwGAD5bIRryWNVC0MDIdJ0CI5I/nwhwdl5xP7288+YPhQdpiwFmmJtDSJhHO3E2ecSTdgnHGOCC1y0jlmDIlttxM3AP3DzNtGlJb8zx8S284lbuB/xsD8lxgt0tI5DBKJbQcSN0gAbWEkRovk/GdmQL8kG8+48YzhYM+5dMJaJM4cfvzxR5mdbH9/GuODH2XWhLVAADQ6DhCrnoG4GBwFo2AUjIKRCwB2Rzo+bGDYXQAAAABJRU5ErkJggg==","orcid":"","institution":"National Center for Atmospheric Research","correspondingAuthor":true,"prefix":"","firstName":"Kwesi","middleName":"Akumenyi","lastName":"Quagraine","suffix":""},{"id":627337624,"identity":"196e5dc7-c2a3-4705-a2b0-dd443f69bd07","order_by":2,"name":"Emmanuel Akalanyabah","email":"","orcid":"","institution":"University of Cape Coast","correspondingAuthor":false,"prefix":"","firstName":"Emmanuel","middleName":"","lastName":"Akalanyabah","suffix":""},{"id":627337630,"identity":"d63f7c51-9641-4f70-a714-3f0d7260b579","order_by":3,"name":"Francis Nkrumah","email":"","orcid":"","institution":"University of Cape Coast","correspondingAuthor":false,"prefix":"","firstName":"Francis","middleName":"","lastName":"Nkrumah","suffix":""},{"id":627337638,"identity":"f51d03e3-851d-497c-96ff-c1f00c7068bb","order_by":4,"name":"Nana Ama Browne Klutse","email":"","orcid":"","institution":"University of Ghana","correspondingAuthor":false,"prefix":"","firstName":"Nana","middleName":"Ama Browne","lastName":"Klutse","suffix":""}],"badges":[],"createdAt":"2026-04-03 20:08:12","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9315964/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9315964/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":108805201,"identity":"207460a2-7104-4221-a65d-189cf88343f1","added_by":"auto","created_at":"2026-05-08 15:25:11","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":4864116,"visible":true,"origin":"","legend":"","description":"","filename":"ReflectiveWAMPaperfin.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9315964/v1_covered_c4eef716-f3c3-4fc3-b616-461e7390e11d.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"High-latitude, low-altitude stratospheric aerosol injection reshapes West African monsoon rainfall and associated dynamics","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":"Stratospheric aerosol injection (SAI), West African Monsoon (WAM), precipitation extremes, dry spell duration, wet spell persistence, climate model intercomparison, HiLLA-SAI","lastPublishedDoi":"10.21203/rs.3.rs-9315964/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9315964/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eStratospheric aerosol injection (SAI) is proposed as a near-term intervention to offset warming, yet its regional impacts remain uncertain. We assess the response of the West African Monsoon (WAM) to high-latitude, low-altitude SAI (HiLLA-SAI) using WACCM6 and UKESM1 simulations. Both models reproduce the seasonal cycle but exhibit systematic biases in rainfall magnitude and extremes. Under SAI, precipitation responses are spatially heterogeneous, with the largest anomalies in July\u0026ndash;August. WACCM6 projects widespread wet biases extending inland from the Guinea Coast, whereas UKESM1 produces weaker and more heterogeneous responses, including drying over the Guinea Highlands and Nigeria. Both models show reduced wet spell persistence along the coast and increased dry spell duration over the Sahel. Dynamically, SAI reduces the meridional temperature gradient and shifts the African Easterly Jet southward, consistent with a reduced northward extent of the rain belt. 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