A Simple Parameterization for the Inland Coastal Aerodynamic Roughness Length within Onshore Flows

A Simple Parameterization for the Inland Coastal Aerodynamic Roughness Length within Onshore Flows | 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 Article A Simple Parameterization for the Inland Coastal Aerodynamic Roughness Length within Onshore Flows James Hlywiak, Jagmohan Singh, Jesus Ruiz-Plancarte, David Flagg, and 6 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7706083/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 12 Jan, 2026 Read the published version in Boundary-Layer Meteorology → Version 1 posted 11 You are reading this latest preprint version Abstract Research and operational numerical weather prediction models rely on bulk-layer parameterization techniques - primarily, the Monin-Obukhov Similarity theory - to compute vertical turbulent fluxes of momentum within the atmospheric surface layer (ASL). In this way, the aerodynamic roughness length and consequently the turbulent drag over land is assumed to be an intrinsic property of the surface, ignoring characteristics of the overlying flow. Although recognized to be invalid near heterogeneous surfaces, to date, no suitable alternatives have been developed for ASL parameterization near coastal environments. In these regions, drastic spatial gradients in surface thermal and roughness properties drive cross-coastal flows, leading to phenomena which directly contradict bulk-flux assumptions. Here, we define a flow-dependent, local, inland coastal aerodynamic roughness length Z_{0c} for onshore flow conditions. Analysis of observations collected from a cross-shore array of inland flux towers anchored at the Monterey Bay, CA coastline from June to October 2021 during the Coastal Land-Air-Sea Interaction (CLASI) campaign reveals significant departures in Z_{0c} from the expected homogeneous values for increasing wind speeds and inland fetches within 8 kilometers of the coast. These findings inform development of a physical framework describing a non-dimensional Z_{0c} as a function of the residence time of the inland flow, a reference height, and a representative homogeneous roughness length. We explore these relationships using large-eddy simulations of a coastal onshore flow scenario to achieve general understanding of the spatial variability in Z_{0c}. Finally, we present a baseline empirical relationship for Z_{0c} based on the CLASI dataset under near-neutral, onshore flow conditions. Coastal meteorology Atmospheric surface-layer Large-eddy simulation Numerical weather prediction Heterogeneous Boundary Layers Full Text Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 12 Jan, 2026 Read the published version in Boundary-Layer Meteorology → Version 1 posted Editorial decision: Revision requested 28 Oct, 2025 Reviews received at journal 27 Oct, 2025 Reviews received at journal 23 Oct, 2025 Reviews received at journal 14 Oct, 2025 Reviewers agreed at journal 27 Sep, 2025 Reviewers agreed at journal 26 Sep, 2025 Reviewers agreed at journal 26 Sep, 2025 Reviewers invited by journal 26 Sep, 2025 Editor assigned by journal 25 Sep, 2025 Submission checks completed at journal 25 Sep, 2025 First submitted to journal 24 Sep, 2025 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. 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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-7706083","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":521499436,"identity":"a57f5d0c-83dd-4e90-9862-48efb0b29bda","order_by":0,"name":"James 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