Aerosol Emissions Dominate Observed and Modeled Hydrological Trends in Arid and Semiarid Regions

Aerosol Emissions Dominate Observed and Modeled Hydrological Trends in Arid and Semiarid Regions | 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 Aerosol Emissions Dominate Observed and Modeled Hydrological Trends in Arid and Semiarid Regions Yanda Zhang, Bjørn Samset, L. Ruby Leung, Laura Wilcox, Daniel Westervelt This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7070418/v2 This work is licensed under a CC BY 4.0 License Status: Posted Version 2 posted You are reading this latest preprint version Show more versions Abstract Arid and semi-arid regions are highly sensitive to hydroclimate changes. In recent decades, precipitation and evapotranspiration have declined across vast global drylands, posing critical challenges to water security and fragile ecosystems. However, these drying trends remain poorly understood and inadequately represented in current climate models. Here, using observations and CMIP6 multi-model simulations, we interpret hydroclimatic changes in (semi-)arid regions and associated model biases by developing a theoretical framework. From an energetic perspective, precipitation and evapotranspiration changes are directly linked to climate forcings through variations in atmospheric diabatic cooling ( δQ ), which is primarily governed by the response of surface sensible heat flux ( δSH down ) to changes in surface shortwave radiation budget ( δDSSR ). Reanalysis and single-forcing simulations reveal that aerosol forcing—rather than greenhouse gases—dominates hydrological changes in dry regions. Since the 1970s, historical aerosol emissions have increased δDSSR and reduced δSH down , the consequent decreases in δQ driving the observed drying trends. In CMIP6 simulations, the substantial underestimation of aerosol-induced solar brightening contributes to pronounced discrepancies with observations. By highlighting the critical role of aerosol effects, this work provides an effective approach for understanding and projecting dryland hydroclimatic responses to shortwave radiative forcings under broader scenarios. Earth and environmental sciences/Climate sciences/Atmospheric science Earth and environmental sciences/Climate sciences/Climate change Earth and environmental sciences/Climate sciences/Climate change/Climate and Earth system modelling Full Text Additional Declarations The authors declare no competing interests. Supplementary Files Supplementary.docx Supplementary information Cite Share Download PDF Status: Posted Version 2 posted You are reading this latest preprint version Show more versions 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-7070418","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":483014887,"identity":"23c38e3e-33de-463b-93c3-386bcfa3e03f","order_by":0,"name":"Yanda Zhang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABB0lEQVRIiWNgGAWjYFACHhBhI8NwAMyzYGCQYGwAMpgJaUnjgWqRIFrLYWQtYAZuLQbnzx78XPDrPA/f8eYDDD8qJBLXzm5u/MBQYZ3YgEvLgXPJ0jP7bvNInjmWwNhzRiJx252DzRIMZ9JxaznYYyDN23Obx+BGjgEzYxtQy43EBgnGtsO4tRzmMf7N23OOx+D+G7iW5h+M//BoOcZjJs3z4wDQFh64ljZgoOHWInmGx8yatyEZ6Je0hINAvxgD/dJmkXAs3RiXFr7zZ4xv8/yxk+M7fvjggx8VNrLbbrc/vvGhxloWlxaFA0CCsQ3COQAXTsChHATkwWb9waNiFIyCUTAKRgEAuZBiJDk2QdcAAAAASUVORK5CYII=","orcid":"https://orcid.org/0000-0003-3135-9123","institution":"Columbia University","correspondingAuthor":true,"prefix":"","firstName":"Yanda","middleName":"","lastName":"Zhang","suffix":""},{"id":483014888,"identity":"406270b8-8abd-45f3-9f8a-55bc23afed0a","order_by":1,"name":"Bjørn Samset","email":"","orcid":"https://orcid.org/0000-0001-8013-1833","institution":"CICERO Center for International Climate Research","correspondingAuthor":false,"prefix":"","firstName":"Bjørn","middleName":"","lastName":"Samset","suffix":""},{"id":483014889,"identity":"6a9319f1-e78e-4e7e-b26b-5714beadfaab","order_by":2,"name":"L. 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In recent decades, precipitation and evapotranspiration have declined across vast global drylands, posing critical challenges to water security and fragile ecosystems. However, these drying trends remain poorly understood and inadequately represented in current climate models. Here, using observations and CMIP6 multi-model simulations, we interpret hydroclimatic changes in (semi-)arid regions and associated model biases by developing a theoretical framework. From an energetic perspective, precipitation and evapotranspiration changes are directly linked to climate forcings through variations in atmospheric diabatic cooling (\u003ci\u003eδQ\u003c/i\u003e), which is primarily governed by the response of surface sensible heat flux (\u003ci\u003eδSH\u003csub\u003edown\u003c/sub\u003e\u003c/i\u003e) to changes in surface shortwave radiation budget (\u003ci\u003eδDSSR\u003c/i\u003e). Reanalysis and single-forcing simulations reveal that aerosol forcing—rather than greenhouse gases—dominates hydrological changes in dry regions. Since the 1970s, historical aerosol emissions have increased \u003ci\u003eδDSSR\u003c/i\u003e and reduced \u003ci\u003eδSH\u003csub\u003edown\u003c/sub\u003e\u003c/i\u003e, the consequent decreases in \u003ci\u003eδQ\u003c/i\u003e driving the observed drying trends. In CMIP6 simulations, the substantial underestimation of aerosol-induced solar brightening contributes to pronounced discrepancies with observations. By highlighting the critical role of aerosol effects, this work provides an effective approach for understanding and projecting dryland hydroclimatic responses to shortwave radiative forcings under broader scenarios.","manuscriptTitle":"Aerosol Emissions Dominate Observed and Modeled Hydrological Trends in Arid and Semiarid Regions","msid":"","msnumber":"","nonDraftVersions":[{"code":2,"date":"2026-01-08 19:47:03","doi":"10.21203/rs.3.rs-7070418/v2","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}},{"code":1,"date":"2025-07-09 14:34:10","doi":"10.21203/rs.3.rs-7070418/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":"9f19e1f1-6e75-4d5a-a068-8b7202721842","owner":[],"postedDate":"January 8th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":51287931,"name":"Earth and environmental sciences/Climate sciences/Atmospheric science"},{"id":51287932,"name":"Earth and environmental sciences/Climate sciences/Climate change"},{"id":51287933,"name":"Earth and environmental sciences/Climate sciences/Climate change/Climate and Earth system modelling"}],"tags":[],"updatedAt":"2026-03-03T16:12:04+00:00","versionOfRecord":[],"versionCreatedAt":"2026-01-08 19:47:03","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v2","identity":"rs-7070418","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7070418","identity":"rs-7070418","version":["v2"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}