Geostationary Observations Reveal Widespread Underestimation of Current Ambient NO2 from Strong Diurnal Variability

Geostationary Observations Reveal Widespread Underestimation of Current Ambient NO2 from Strong Diurnal Variability | 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 Geostationary Observations Reveal Widespread Underestimation of Current Ambient NO 2 from Strong Diurnal Variability Jing Wei, Zhanqing Li, Fan Cheng, Zeyu Yang, Jun Wang, Kai Yang, and 6 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7968663/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 Ambient nitrogen dioxide (NO2) is a short-lived but harmful pollutant, and its accurate estimation remains challenging. Traditional polar-orbiting satellites cannot capture its diurnal variability due to their once-daily early-afternoon overpasses. Thus, we integrate GEMS geostationary satellite observations with GEOS-CF model simulations, applying a space-time machine learning model to generate the first gapless, hourly surface NO2 dataset across China with full 24-hour coverage. A distinct bimodal pattern in surface NO₂ levels is observed, exhibiting a large diurnal amplitude (71%) with a morning peak, midday decline, and stronger evening rebound. Daytime levels are driven by photochemical activity and enhanced vertical mixing associated with higher boundary layer heights (BLH), whereas nighttime concentrations are influenced by a shallow BLH and higher humidity that suppress mixing and chemical reactions. This contrast aligns with the much lower diurnal variability in tropospheric NO2 (36%). Incorporating GEMS hourly observations further improves estimates of daily (24-hour) mean surface NO2 (R2 = 0.88), particularly in rural regions, compared to results derived from polar-orbiting TROPOMI satellites. TROPOMI shows widespread underestimation of daily NO2 exposure across 85% of the domain due to its once-daily overpass in the early afternoon. Thus, it often misses high-pollution events and underreports days exceeding the World Health Organization’s daily Interim Target 1 (120 µg m-3) and the air quality guideline (25 µg m-3), respectively. Consequently, using this polar-orbiting-derived estimate results in 2,200 fewer premature deaths from acute ambient NO2 exposure, 11,500 fewer deaths from chronic exposure, and 850 fewer asthma cases compared with estimates based on geostationary GEMS observations in 2023. These findings underscore the urgent need to capture the full diurnal dynamics of ambient NO2 for accurate exposure assessment and more effective environmental health policies. Earth and environmental sciences/Environmental sciences/Environmental impact Earth and environmental sciences/Planetary science/Atmospheric chemistry Full Text Additional Declarations There is NO Competing Interest. Supplementary Files ChinaGEONO2SupplementaryInformation.docx Geostationary Observations Reveal Widespread Underestimation of Current Ambient NO2 from Strong Diurnal Variability 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-7968663","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":536441941,"identity":"e8659188-db15-4316-89ca-8ea78b09bd65","order_by":0,"name":"Jing Wei","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAzElEQVRIiWNgGAWjYBACxmYwJSHHwAOi2UjQYky8FhhIbCBaC3M77+HXPBUW6dt5zhgwfCg7zMA/u4GQw/jSrHnOSOTu7O0xYJxx7jCDxJ0DhLTwmBnntknkbjjPY8DM23aYwUAigRgt/yTSDUBa/hKpxfhxboNEgsHZHgNmRmJtYf5zTMJwZ8+xgoM959J5JG4Q0GLYf8b444yaOnlznuSND36UWcvxzyCkpYGBTQLEMADiA0DMg189EMgDo+YDTMsoGAWjYBSMAqwAALEaPSCj0QzSAAAAAElFTkSuQmCC","orcid":"","institution":"Peking University","correspondingAuthor":true,"prefix":"","firstName":"Jing","middleName":"","lastName":"Wei","suffix":""},{"id":536441942,"identity":"f3d2e32c-187f-4316-a133-4eb011f25a94","order_by":1,"name":"Zhanqing Li","email":"","orcid":"https://orcid.org/0000-0001-6737-382X","institution":"University of Maryland, College Park","correspondingAuthor":false,"prefix":"","firstName":"Zhanqing","middleName":"","lastName":"Li","suffix":""},{"id":536441943,"identity":"36121979-3b82-48d0-b6a5-663020b407f8","order_by":2,"name":"Fan Cheng","email":"","orcid":"","institution":"Shanghai Jiao Tong University","correspondingAuthor":false,"prefix":"","firstName":"Fan","middleName":"","lastName":"Cheng","suffix":""},{"id":536441944,"identity":"28da2824-08b0-4512-b2be-94ba43d7794f","order_by":3,"name":"Zeyu Yang","email":"","orcid":"","institution":"Tsinghua University","correspondingAuthor":false,"prefix":"","firstName":"Zeyu","middleName":"","lastName":"Yang","suffix":""},{"id":536441945,"identity":"f3592d64-ef11-43f5-ab41-0520873aa70e","order_by":4,"name":"Jun Wang","email":"","orcid":"https://orcid.org/0000-0002-7334-0490","institution":"University of Iowa","correspondingAuthor":false,"prefix":"","firstName":"Jun","middleName":"","lastName":"Wang","suffix":""},{"id":536441946,"identity":"5da9969e-be6f-44a9-a9e3-6cdda1ab2640","order_by":5,"name":"Kai Yang","email":"","orcid":"","institution":"University of Maryland College Park","correspondingAuthor":false,"prefix":"","firstName":"Kai","middleName":"","lastName":"Yang","suffix":""},{"id":536441947,"identity":"d2601f1c-ad24-4f12-a211-154f34393568","order_by":6,"name":"Jhoon Kim","email":"","orcid":"https://orcid.org/0000-0002-1508-9218","institution":"Yonsei University","correspondingAuthor":false,"prefix":"","firstName":"Jhoon","middleName":"","lastName":"Kim","suffix":""},{"id":536441948,"identity":"d8151461-ad19-45a0-afd9-6009b2911b62","order_by":7,"name":"Klaas Boersma","email":"","orcid":"https://orcid.org/0000-0002-4591-7635","institution":"Wageningen University","correspondingAuthor":false,"prefix":"","firstName":"Klaas","middleName":"","lastName":"Boersma","suffix":""},{"id":536441949,"identity":"bff52dc9-66bb-4341-b2e7-d324ae66adf1","order_by":8,"name":"Susan Anenberg","email":"","orcid":"","institution":"George Washington University","correspondingAuthor":false,"prefix":"","firstName":"Susan","middleName":"","lastName":"Anenberg","suffix":""},{"id":536441950,"identity":"29c06285-a7ea-4c42-968f-980cf180ccf0","order_by":9,"name":"Gaige Kerr","email":"","orcid":"","institution":"George Washington University","correspondingAuthor":false,"prefix":"","firstName":"Gaige","middleName":"","lastName":"Kerr","suffix":""},{"id":536441951,"identity":"0e0f5954-a98b-4202-88ef-8e5de9f2a9e9","order_by":10,"name":"Jicheng Gong","email":"","orcid":"","institution":"Peking University","correspondingAuthor":false,"prefix":"","firstName":"Jicheng","middleName":"","lastName":"Gong","suffix":""},{"id":536441952,"identity":"2acf1a7b-cca7-481e-9c95-a9ac94e657f1","order_by":11,"name":"Tong Zhu","email":"","orcid":"https://orcid.org/0000-0002-2752-7924","institution":"Peking University","correspondingAuthor":false,"prefix":"","firstName":"Tong","middleName":"","lastName":"Zhu","suffix":""}],"badges":[],"createdAt":"2025-10-28 16:40:22","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7968663/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7968663/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":95223788,"identity":"3623af34-d903-4e8b-86ea-642ae3a712c9","added_by":"auto","created_at":"2025-11-05 16:22:50","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1652267,"visible":true,"origin":"","legend":"","description":"","filename":"ChinaGEONO2ManuscriptSubmission.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7968663/v1_covered_b3cb2875-103a-45c0-84d2-a58c33b06d0f.pdf"},{"id":94820950,"identity":"f07f3421-e249-4c8a-ae42-e6a4ee4b7ea9","added_by":"auto","created_at":"2025-10-31 06:05:56","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":12908363,"visible":true,"origin":"","legend":"Geostationary Observations Reveal Widespread Underestimation of Current Ambient NO2 from Strong Diurnal Variability","description":"","filename":"ChinaGEONO2SupplementaryInformation.docx","url":"https://assets-eu.researchsquare.com/files/rs-7968663/v1/7472752d7fb04cf14ea3bf86.docx"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"\u003cp\u003eGeostationary Observations Reveal Widespread Underestimation of Current Ambient NO\u003csub\u003e2\u003c/sub\u003e from Strong Diurnal Variability\u003c/p\u003e","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"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":"","lastPublishedDoi":"10.21203/rs.3.rs-7968663/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7968663/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"Ambient nitrogen dioxide (NO2) is a short-lived but harmful pollutant, and its accurate estimation remains challenging. Traditional polar-orbiting satellites cannot capture its diurnal variability due to their once-daily early-afternoon overpasses. Thus, we integrate GEMS geostationary satellite observations with GEOS-CF model simulations, applying a space-time machine learning model to generate the first gapless, hourly surface NO2 dataset across China with full 24-hour coverage. A distinct bimodal pattern in surface NO₂ levels is observed, exhibiting a large diurnal amplitude (71%) with a morning peak, midday decline, and stronger evening rebound. Daytime levels are driven by photochemical activity and enhanced vertical mixing associated with higher boundary layer heights (BLH), whereas nighttime concentrations are influenced by a shallow BLH and higher humidity that suppress mixing and chemical reactions. This contrast aligns with the much lower diurnal variability in tropospheric NO2 (36%). Incorporating GEMS hourly observations further improves estimates of daily (24-hour) mean surface NO2 (R2 = 0.88), particularly in rural regions, compared to results derived from polar-orbiting TROPOMI satellites. TROPOMI shows widespread underestimation of daily NO2 exposure across 85% of the domain due to its once-daily overpass in the early afternoon. Thus, it often misses high-pollution events and underreports days exceeding the World Health Organization’s daily Interim Target 1 (120 µg m-3) and the air quality guideline (25 µg m-3), respectively. Consequently, using this polar-orbiting-derived estimate results in 2,200 fewer premature deaths from acute ambient NO2 exposure, 11,500 fewer deaths from chronic exposure, and 850 fewer asthma cases compared with estimates based on geostationary GEMS observations in 2023. These findings underscore the urgent need to capture the full diurnal dynamics of ambient NO2 for accurate exposure assessment and more effective environmental health policies.","manuscriptTitle":"Geostationary Observations Reveal Widespread Underestimation of Current Ambient NO2 from Strong Diurnal Variability","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-10-31 06:05:50","doi":"10.21203/rs.3.rs-7968663/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":"4338fc11-fa04-460d-afc3-74c43872c010","owner":[],"postedDate":"October 31st, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":57200979,"name":"Earth and environmental sciences/Environmental sciences/Environmental impact"},{"id":57200980,"name":"Earth and environmental sciences/Planetary science/Atmospheric chemistry"}],"tags":[],"updatedAt":"2025-11-04T07:55:44+00:00","versionOfRecord":[],"versionCreatedAt":"2025-10-31 06:05:50","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7968663","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7968663","identity":"rs-7968663","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}