Drivers of mesoscale convective aggregation and spatial humidity variability in the tropical western Pacific

Drivers of mesoscale convective aggregation and spatial humidity variability in the tropical western Pacific | 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 Drivers of mesoscale convective aggregation and spatial humidity variability in the tropical western Pacific Adrian Tompkins, Alejandro Casallas, Michie de Vera This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4429393/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 24 Feb, 2025 Read the published version in npj Climate and Atmospheric Science → Version 1 posted 11 You are reading this latest preprint version Abstract Idealized models show aggregation of tropical convection on the mesoscale driven by radiative-cloud feedbacks. We apply a multivariate analysis of column humidity, precipitation and sea surface temperature (SST) observations to mesoscale domains in the tropical western Pacific to demonstrate that in boreal summer and autumn, convection remains spatially random despite radiative-feedbacks acting to aggregate convection. Instead, in winter and spring, a weak meridional SST gradient exists and convection is usually clustered over the regions of warmest SSTs, with significant meridional humidity gradients. However, this is sporadically interrupted by episodes of convection migration to the coldest SSTs and limited spatial humidity variance. These episodes are the result of westward propagating equatorial Rossby waves, which act to remove meridional humidity gradients. It thus appears that the drivers of mesoscale convective clustering and humidity variability in the Pacific warm pool are the SST gradients and equatorial wave dynamics. Earth and environmental sciences/Climate sciences/Atmospheric science/Atmospheric dynamics Earth and environmental sciences/Climate sciences/Climate change Full Text Additional Declarations (Not answered) Supplementary Files SupplemetaryInfoReversalsObs.pdf Cite Share Download PDF Status: Published Journal Publication published 24 Feb, 2025 Read the published version in npj Climate and Atmospheric Science → Version 1 posted Editorial decision: revise 20 Jun, 2024 Review # 3 received at journal 18 Jun, 2024 Review # 1 received at journal 12 Jun, 2024 Review # 2 received at journal 07 Jun, 2024 Reviewer # 3 agreed at journal 24 May, 2024 Reviewer # 2 agreed at journal 24 May, 2024 Reviewer # 1 agreed at journal 24 May, 2024 Reviewers invited by journal 22 May, 2024 Editor assigned by journal 17 May, 2024 Submission checks completed at journal 17 May, 2024 First submitted to journal 16 May, 2024 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. 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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-4429393","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":305531119,"identity":"b2857eec-a4b6-45d8-a29e-f01a40889cad","order_by":0,"name":"Adrian Tompkins","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAtElEQVRIiWNgGAWjYJACxgYDBgZ+ZjBbgrByHpgWyWYgDdRCWA9EC5AwOAChCWuxZ+9Oezij4I698XHm548LGCzqCNvCc3a74QaDZ4nbDrMZNs8gymESudskHxgcTjA7zMPYzEOKFnvjZpK0bDA4zLiBmWgtZ4B+mWFwOHEG0C+zZxhISDYQ0sLe3rvtYc+fw/b8/YcffC6oqOMnaAsQsMFZzAwGxGhA1TIKRsEoGAWjAAsAAHi8NShd8IqkAAAAAElFTkSuQmCC","orcid":"https://orcid.org/0000-0003-0975-6691","institution":"International Centre for Theoretical Physics (ICTP)","correspondingAuthor":true,"prefix":"","firstName":"Adrian","middleName":"","lastName":"Tompkins","suffix":""},{"id":305531120,"identity":"41c6bdad-d5e3-4efd-9b79-e0523e10eccf","order_by":1,"name":"Alejandro Casallas","email":"","orcid":"https://orcid.org/0000-0002-1988-5035","institution":"International Centre for Theoretical Physics (ICTP)","correspondingAuthor":false,"prefix":"","firstName":"Alejandro","middleName":"","lastName":"Casallas","suffix":""},{"id":305531121,"identity":"7b27c05b-31d2-4c62-bc97-7a3a7ae74613","order_by":2,"name":"Michie de Vera","email":"","orcid":"","institution":"University of Illinois Urbana-Champaign","correspondingAuthor":false,"prefix":"","firstName":"Michie","middleName":"","lastName":"de Vera","suffix":""}],"badges":[],"createdAt":"2024-05-16 08:00:32","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4429393/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4429393/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1038/s41612-024-00848-2","type":"published","date":"2025-02-24T05:00:00+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":77106117,"identity":"0aa4af22-7bac-46ef-a074-f1d986e40c47","added_by":"auto","created_at":"2025-02-25 08:10:22","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":6588014,"visible":true,"origin":"","legend":"","description":"","filename":"2024humiditydrivers.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4429393/v1_covered_6c6203ba-aabd-4a29-8087-a3e53f2e0d67.pdf"},{"id":57656852,"identity":"5c999eab-23e6-4b0e-ba37-02b2bd87878f","added_by":"auto","created_at":"2024-06-04 01:59:34","extension":"pdf","order_by":12,"title":"","display":"","copyAsset":false,"role":"supplement","size":4646693,"visible":true,"origin":"","legend":"","description":"","filename":"SupplemetaryInfoReversalsObs.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4429393/v1/8584ed403d406fe9a074aff7.pdf"}],"financialInterests":"(Not answered)","formattedTitle":"Drivers of mesoscale convective aggregation and spatial humidity variability in the tropical western Pacific","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":"npj-climate-and-atmospheric-science","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"npjclimatsci","sideBox":"Learn more about [npj Climate and Atmospheric Science](http://www.nature.com/npjclimatsci/)","snPcode":"41612","submissionUrl":"https://submission.springernature.com/new-submission/41612/3","title":"npj Climate and Atmospheric Science","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"NPJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-4429393/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4429393/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"Idealized models show aggregation of tropical convection on the mesoscale driven by radiative-cloud feedbacks. We apply a multivariate analysis of column humidity, precipitation and sea surface temperature (SST) observations to mesoscale domains in the tropical western Pacific to demonstrate\r\n that in boreal summer and autumn, convection remains spatially random despite radiative-feedbacks acting to aggregate convection. Instead, in winter and spring, a weak meridional SST gradient exists and convection\r\n is usually clustered over the regions of warmest SSTs, with significant \r\n meridional humidity gradients. However, this is sporadically \r\n interrupted by episodes of convection migration to the coldest SSTs and limited spatial humidity variance. These episodes are the result of westward propagating equatorial Rossby waves, which act to remove meridional humidity gradients. 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