The influence of near-field fluxes on seasonal carbon dioxide enhancements: Results from the Indianapolis Flux Experiment (INFLUX)

The influence of near-field fluxes on seasonal carbon dioxide enhancements: Results from the Indianapolis Flux Experiment (INFLUX) | 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 The influence of near-field fluxes on seasonal carbon dioxide enhancements: Results from the Indianapolis Flux Experiment (INFLUX) NATASHA MILES, Kenneth J. Davis, Scott J. Richardson, Thomas Lauvaux, and 8 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-66160/v2 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 30 Jan, 2021 Read the published version in Carbon Balance and Management → Version 2 posted 4 You are reading this latest preprint version Show more versions Abstract Background Networks of tower-based CO 2 mole fraction sensors have been deployed in and around cities across the world to quantify anthropogenic CO 2 emissions from metropolitan areas. A critical aspect in these approaches is the separation of atmospheric signatures from distant sources and sinks (i.e., the background) from local emissions and biogenic fluxes. We examined CO 2 enhancements compared to forested and agricultural background towers in Indianapolis, Indiana, USA, as a function of season and compared them to modeled results, as a part of the Indianapolis Flux (INFLUX) project. Results At the INFLUX urban tower sites, daytime growing season enhancement on a monthly timescale was up to 4.3 – 6.5 ppm, 2.6 times as large as those in the dormant season, on average. The enhancement differed significantly depending on choice of background and time of year, being 2.8 ppm higher in June and 1.8 ppm lower in August using a forested background tower compared to an agricultural background tower. A prediction based on land cover and observed CO 2 fluxes showed that differences in phenology and drawdown intensities drove measured differences in enhancements. Forward modelled CO 2 enhancements using fossil fuel and biogenic fluxes indicated growing season model-data mismatch of 1.1 ± 1.7 ppm for the agricultural background and 2.1 ± 0.5 ppm for the forested background, corresponding to 25 – 29 % of the modelled CO 2 enhancements. The model-data total CO 2 mismatch during the dormant season was low, – 0.1 ± 0.5 ppm. Conclusions Because growing season biogenic fluxes at the background towers are large, the urban enhancements must be disentangled from the biogenic signal, and growing season increases in CO 2 enhancement could be misinterpreted as increased anthropogenic fluxes if the background ecosystem CO 2 drawdown is not considered. The magnitude and timing of enhancements depend on the land cover type and net fluxes surrounding each background tower, so a simple box model is not appropriate for interpretation of these data. Quantification of the seasonality and magnitude of the biological fluxes in the study region using high-resolution and detailed biogenic models is necessary for the interpretation of tower-based urban CO 2 networks for cities with significant vegetation. Atmospheric Sciences Carbon dioxide urban greenhouse gas fluxes background INFLUX anthropogenic biogenic Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Full Text Supplementary Files Supplement.docx Cite Share Download PDF Status: Published Journal Publication published 30 Jan, 2021 Read the published version in Carbon Balance and Management → Version 2 posted Editor assigned by journal 16 Dec, 2020 Editorial decision: Accept 16 Dec, 2020 Submission checks completed at journal 16 Dec, 2020 Editor invited by journal 16 Dec, 2020 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. 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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-66160","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research","associatedPublications":[],"authors":[{"id":7082953,"identity":"a2d13899-67f6-4ae5-a06f-dd1cbc6bfafd","order_by":0,"name":"NATASHA MILES","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAq0lEQVRIiWNgGAWjYFACxsYDDAw2EDYPkVoagFrSSNLCwADUcpgELeZihxsOfPhzPk9+RgLjg7dtRGixnJ3YcHBm2+1igxsJzIZzidFicDux4TBvw+3EDRIJbNK8RGv58+dc4vwZCey/idfCwHYgseFGAhsz0VoO9rYlFxucedgsOeccUVrSHz748ccuT749+eCHN2VEaIGBBFCckqAeomUUjIJRMApGAQ4AAItEPnzVXBK/AAAAAElFTkSuQmCC","orcid":"https://orcid.org/0000-0003-4266-2726","institution":"Pennsylvania State University University Park","correspondingAuthor":true,"submittingAuthor":false,"prefix":"","firstName":"NATASHA","middleName":"","lastName":"MILES","suffix":""},{"id":7082954,"identity":"0bc04dd9-b8d8-4798-bdf5-074471c5fe02","order_by":1,"name":"Kenneth J. Davis","email":"","orcid":"","institution":"Pennsylvania State University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Kenneth","middleName":"J.","lastName":"Davis","suffix":""},{"id":7082955,"identity":"7a8d890f-12bc-44b8-88ae-ba2dd7cf71ba","order_by":2,"name":"Scott J. Richardson","email":"","orcid":"","institution":"Pennsylvania State University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Scott","middleName":"J.","lastName":"Richardson","suffix":""},{"id":7082956,"identity":"3a81e5da-719d-40fd-a787-f8c2aeeed9f4","order_by":3,"name":"Thomas Lauvaux","email":"","orcid":"","institution":"Laboratoire des sciences du climat et de l'environnement","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Thomas","middleName":"","lastName":"Lauvaux","suffix":""},{"id":7082957,"identity":"1eb5b0b4-849e-44f3-8647-07c057ff3ef5","order_by":4,"name":"Douglas K. Martins","email":"","orcid":"","institution":"FLIR Systems, Inc","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Douglas","middleName":"K.","lastName":"Martins","suffix":""},{"id":7082958,"identity":"f452c0d2-b77a-4201-92c1-bebc2c5ddd42","order_by":5,"name":"A.J. Deng","email":"","orcid":"","institution":"Utopus Insights Inc","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"A.J.","middleName":"","lastName":"Deng","suffix":""},{"id":7082959,"identity":"9f7d290d-dd81-4102-8994-44824cd1c134","order_by":6,"name":"Nikolay Balashov","email":"","orcid":"","institution":"NASA Goddard Space Flight Center","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Nikolay","middleName":"","lastName":"Balashov","suffix":""},{"id":7082960,"identity":"78662e76-f430-413e-a0fb-460ade5feb15","order_by":7,"name":"Kevin R. Gurney","email":"","orcid":"","institution":"Northern Arizona University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Kevin","middleName":"R.","lastName":"Gurney","suffix":""},{"id":7082961,"identity":"dd9f5260-1a01-4c54-ab6f-92989ccee488","order_by":8,"name":"Jianming Liang","email":"","orcid":"","institution":"Environmental Systems Research Institute","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Jianming","middleName":"","lastName":"Liang","suffix":""},{"id":7082962,"identity":"8772db46-101a-491c-bc37-2e377aea72a5","order_by":9,"name":"Geoff Roest","email":"","orcid":"","institution":"Northern Arizona University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Geoff","middleName":"","lastName":"Roest","suffix":""},{"id":7082963,"identity":"3dce209c-40b2-4745-b679-dd7463df8e02","order_by":10,"name":"Jonathan A. Wang","email":"","orcid":"","institution":"University of California Irvine","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Jonathan","middleName":"A.","lastName":"Wang","suffix":""},{"id":7082964,"identity":"9bfabb53-bacf-4542-a175-14967bbef7b4","order_by":11,"name":"Jocelyn C. Turnbull","email":"","orcid":"","institution":"GNS Science","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Jocelyn","middleName":"C.","lastName":"Turnbull","suffix":""}],"badges":[],"createdAt":"2020-08-26 12:27:51","currentVersionCode":2,"declarations":"","doi":"10.21203/rs.3.rs-66160/v2","doiUrl":"https://doi.org/10.21203/rs.3.rs-66160/v2","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1186/s13021-020-00166-z","type":"published","date":"2021-01-30T15:02:25+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":4783910,"identity":"028ad32e-9f24-4f5d-9ba3-6cae3d650d96","added_by":"auto","created_at":"2021-01-07 17:57:07","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":51316,"visible":true,"origin":"","legend":"Landcover map of the Indianapolis, IN, region. The numbers 01–14 indicate tower site locations. Towers 05 and 12 were decommissioned in September 2015 and April 2013, respectively. Tower 14 was installed in April 2017 as an additional background site. (Multi-Resolution Land Characteristics Consortium 2020; Jin et al. 2013). ","description":"","filename":"Fig1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-66160/v2/6bdad724ec256c9f7f94cbc2.jpg"},{"id":4783909,"identity":"a76afaee-299b-4d81-aca6-22e8acf8be8b","added_by":"auto","created_at":"2021-01-07 17:57:06","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":21144,"visible":true,"origin":"","legend":"(a) Mean annual cycle of biological CO2 fluxes (net ecosystem exchange; NEE) for a forest site (dark green), a corn site (yellow) and a soybean site (light green). The forest fluxes are the 5-year mean measured at the Morgan Monroe State Forest (Kim et al. 2015) and the corn and soybean fluxes are the 3-year mean measured in Bondville, Illinois (Hollinger et al. 2005). (b) Domain-averaged 31-day median (fossil fuel (Hestia) emissions as a function of time of year for 2014. ","description":"","filename":"Fig2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-66160/v2/79f4d2466e6556b323bc50bd.jpg"},{"id":4783977,"identity":"0c7ab8aa-c919-494f-af2b-84b23a9f1e5d","added_by":"auto","created_at":"2021-01-07 18:00:07","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":57143,"visible":true,"origin":"","legend":"Percentage land cover types for a 10-km radius circle encompassing approximately 80 % of the footprint for each tower. (Han et al. 2012; United States Department of Agriculture National Agriculture Statistics Service 2019; https://nassgeodata.gmu.edu/CropScape/). https://nassgeodata.gmu.edu/CropScape/. The grass category also includes hay/pasture. Towers are ordered based on urban fraction (including open-, low-, medium-, and high-density developed areas). Towers 09, 01, and 14 are potential background towers.","description":"","filename":"Fig3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-66160/v2/a1039492806f72f818485804.jpg"},{"id":4783891,"identity":"52c31bd4-fad5-4380-9e2b-ca8a4994cc54","added_by":"auto","created_at":"2021-01-07 17:54:06","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":31874,"visible":true,"origin":"","legend":"Composited 31-day running median afternoon-average CO2 enhancements from Tower 09 for each of the towers, using data from January 2013 through December 2018. The towers are ordered by urban fraction (including high-, medium-, and low-density urban land cover, as discussed in Section 3.1. Tickmarks indicate the beginning of each time period. Data for which Tower 01 or Tower 09 was influenced by the urban plume were excluded from the analysis (WSW and NE). Dashed lines indicate July 15. Non-background towers deployed for less than 3 years are not shown (Towers 05 and 12). Tower 09 enhancement compared to Tower 09 is zero, by definition, but the row is included for consistency. ","description":"","filename":"Fig4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-66160/v2/3f3aaad1304b33ac1919799d.jpg"},{"id":4783913,"identity":"951d140b-f596-42bb-b2f1-a50235500eeb","added_by":"auto","created_at":"2021-01-07 17:57:07","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":16820,"visible":true,"origin":"","legend":"Observed CO2 enhancement using Tower 09 (agricultural) as a background (green) and Tower 01 (forested) as a background (blue), composited over 2013 – 2018, and averaged over INFLUX urban towers. Wind directions for which either Tower 01 or Tower 09 are in the urban plume have been excluded. Only afternoon hours (1200 – 1700 LST) are included. Error bars indicate the standard error amongst the urban towers.","description":"","filename":"Fig5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-66160/v2/3a3e3b869d6a7a04f3b66905.jpg"},{"id":4783900,"identity":"f60d1cc7-3d5a-46df-9582-6af40fdf3470","added_by":"auto","created_at":"2021-01-07 17:54:07","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":26250,"visible":true,"origin":"","legend":"(a) 31-day running median CO2 difference between Towers 09 and Tower 01 for 2014 (black line) and composited for 2013 – 2018 (shaded area), with the width of the shaded area indicating the standard deviation amongst years. Data for which either Tower 01 or Tower 09 were influenced by the urban plume were excluded from the analysis. (b) Predicted seasonal pattern of difference in CO2 mole fraction (dimensionless, see Eq. 2) between Tower 01 and Tower 09, based on typical forest, corn and soy fluxes shown in Fig. 2a, and forest and agricultural land cover differences within 10 km of each site, between the two sites. (c) Forward modelled (using Hestia and VPRM) 31-day running median CO2 difference (black) between Towers 09 and 01 for 2014. Difference between observed and modelled Tower 01 – Tower 09 difference is shown in gray. ","description":"","filename":"Fig6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-66160/v2/ca7b7e7747c6f47d2813d0ae.jpg"},{"id":4783894,"identity":"96d262cc-0e8a-433b-af31-02708e893afe","added_by":"auto","created_at":"2021-01-07 17:54:07","extension":"jpg","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":16288,"visible":true,"origin":"","legend":"Schematic illustrating the “differential footprint” concept, as opposed to a simple box model. The green area indicates rural landcover surrounding the background tower and the gray area indicates urban landcover. The ellipses indicate the areas contributing the majority of the signal for each tower, since the influence decreases exponentially with distance from the tower. 80% of the influence for the INFLUX towers is within 10 km, on average, and for example, Towers 01 and 02 are separated by 43 km. ","description":"","filename":"Fig7.jpg","url":"https://assets-eu.researchsquare.com/files/rs-66160/v2/5e68ea80ee93c7ca8824ee1f.jpg"},{"id":4783899,"identity":"5a90ce20-0530-44f2-8d2a-1e0b5ac0f1bd","added_by":"auto","created_at":"2021-01-07 17:54:07","extension":"jpg","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":25763,"visible":true,"origin":"","legend":"(a) Modelled CO2 enhancement using Tower 09 (agricultural) as a background (green) and Tower 01 (forested) as a background (blue), averaged over INFLUX urban towers for 2014. Wind directions for which either Tower 01 or Tower 09 are in the urban plume have been excluded. Only afternoon hours (1200 – 1700 LST) are included. Error bars indicate the standard error amongst the urban towers. (b) Model-data mismatch. Note that there was an instrument failure at Tower 09 for September – December 2014. (c) Percent mismatch, i.e., model-data mismatch divided by the modelled CO2 enhancement. ","description":"","filename":"Fig8.jpg","url":"https://assets-eu.researchsquare.com/files/rs-66160/v2/9241507aeff54a01eee21fa0.jpg"},{"id":4783914,"identity":"c19adb61-d523-44a6-ab53-89ccfd577316","added_by":"auto","created_at":"2021-01-07 17:57:07","extension":"jpg","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":15460,"visible":true,"origin":"","legend":"Composited 31-day running median CO2 differences between Towers 09 and 14, both agricultural background towers. As for the previous results, data for which Tower 01 or Tower 09 was influenced by the urban plume were excluded from the analysis (WSW and NE). Tower 14 was not significantly affected by the urban plume. ","description":"","filename":"Fig9.jpg","url":"https://assets-eu.researchsquare.com/files/rs-66160/v2/02461a9fceace975df6f2871.jpg"},{"id":13572019,"identity":"f108ab05-a14c-4327-94eb-d14723561da6","added_by":"auto","created_at":"2021-09-17 03:49:52","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2137177,"visible":true,"origin":"","legend":"","description":"","filename":"Milesetal2020INFLUXbgsubmittededit2.pdf","url":"https://assets-eu.researchsquare.com/files/rs-66160/v2_covered.pdf"},{"id":13526777,"identity":"6189a122-c73e-4e98-a5df-f884d11c7e24","added_by":"auto","created_at":"2021-09-17 00:53:24","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1999253,"visible":true,"origin":"","legend":"","description":"","filename":"Milesetal2020INFLUXbgsubmitted.pdf","url":"https://assets-eu.researchsquare.com/files/rs-66160/v1_covered.pdf"},{"id":4784015,"identity":"860e6be6-69bb-4437-bd40-561f07151318","added_by":"auto","created_at":"2021-01-07 18:03:11","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2930954,"visible":true,"origin":"","legend":"","description":"","filename":"Milesetal2020INFLUXbgsubmittededit2.pdf","url":"https://assets-eu.researchsquare.com/files/rs-66160/v2_stamped.pdf"},{"id":4783912,"identity":"5d1782f8-0980-44e0-8d8b-a671ca990c51","added_by":"auto","created_at":"2021-01-07 17:57:07","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":1201523,"visible":true,"origin":"","legend":"","description":"","filename":"Supplement.docx","url":"https://assets-eu.researchsquare.com/files/rs-66160/v2/7852206cbaaac0542738b1b3.docx"}],"financialInterests":"","formattedTitle":"\u003cp\u003eThe influence of near-field fluxes on seasonal carbon dioxide enhancements:\u0026nbsp;Results from the Indianapolis Flux Experiment (INFLUX)\u003c/p\u003e","fulltext":[{"header":"Full Text","content":"\u003cp\u003eThis preprint is available for \u003ca href='/article/rs-66160/latest.pdf' target='_blank'\u003edownload as a PDF\u003c/a\u003e.\u003c/p\u003e"}],"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":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"carbon-balance-and-management","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"cbam","sideBox":"Learn more about [Carbon Balance and Management](https://cbmjournal.biomedcentral.com/)","snPcode":"13021","submissionUrl":"https://submission.nature.com/new-submission/13021/3","title":"Carbon Balance and Management","twitterHandle":"@BioMedCentral","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Carbon dioxide, urban, greenhouse gas, fluxes, background, INFLUX, anthropogenic, biogenic","lastPublishedDoi":"10.21203/rs.3.rs-66160/v2","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-66160/v2","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eBackground\u003c/strong\u003e\u003c/p\u003e\u003cp\u003eNetworks of tower-based CO\u003csub\u003e2\u003c/sub\u003e mole fraction sensors have been deployed in and around cities across the world to quantify anthropogenic CO\u003csub\u003e2\u003c/sub\u003e emissions from metropolitan areas. A critical aspect in these approaches is the separation of atmospheric signatures from distant sources and sinks (i.e., the background) from local emissions and biogenic fluxes. We examined CO\u003csub\u003e2\u003c/sub\u003e enhancements compared to forested and agricultural background towers in Indianapolis, Indiana, USA, as a function of season and compared them to modeled results, as a part of the Indianapolis Flux (INFLUX) project.\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eResults\u003c/strong\u003e\u003c/p\u003e\u003cp\u003eAt the INFLUX urban tower sites, daytime growing season enhancement on a monthly timescale was up to 4.3 – 6.5 ppm, 2.6 times as large as those in the dormant season, on average.\u0026nbsp;The enhancement differed significantly depending on choice of background and time of year, being 2.8 ppm higher in June and 1.8 ppm lower in August using a forested background tower compared to an agricultural background tower.\u0026nbsp;A prediction based on land cover and observed CO\u003csub\u003e2\u003c/sub\u003e fluxes showed that differences in phenology and drawdown intensities drove measured differences in enhancements. \u0026nbsp;\u0026nbsp;Forward modelled CO\u003csub\u003e2\u003c/sub\u003e enhancements using fossil fuel and biogenic fluxes indicated growing season model-data mismatch of 1.1 ± 1.7 ppm for the agricultural background and 2.1 ± 0.5 ppm for the forested background, corresponding to 25 – 29 % of the modelled CO\u003csub\u003e2 \u003c/sub\u003eenhancements. The model-data total CO\u003csub\u003e2\u003c/sub\u003e mismatch during the dormant season was low, – 0.1 ± 0.5 ppm.\u0026nbsp;\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eConclusions\u003c/strong\u003e\u003c/p\u003e\u003cp\u003eBecause growing season biogenic fluxes at the background towers are large, the urban enhancements must be disentangled from the biogenic signal, and growing season increases in CO\u003csub\u003e2\u003c/sub\u003e enhancement could be misinterpreted as increased anthropogenic fluxes if the background ecosystem CO\u003csub\u003e2\u003c/sub\u003e drawdown is not considered.\u0026nbsp;The magnitude and timing of enhancements depend on the land cover type and net fluxes surrounding each background tower, so a simple box model is not appropriate for interpretation of these data.\u0026nbsp;Quantification of the seasonality and magnitude of the biological fluxes in the study region using high-resolution and detailed biogenic models is necessary for the interpretation of tower-based urban CO\u003csub\u003e2\u003c/sub\u003e networks for cities with significant vegetation.\u003c/p\u003e","manuscriptTitle":"The influence of near-field fluxes on seasonal carbon dioxide enhancements:\u0026nbsp;Results from the Indianapolis Flux Experiment (INFLUX)","msid":"","msnumber":"","nonDraftVersions":[{"code":2,"date":"2021-01-07 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