The impact of wind speed measurement method on MRT and UTCI values ​​in limited air flow conditions within urban green areas.

The impact of wind speed measurement method on MRT and UTCI values ​​in limited air flow conditions within urban green areas. | 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 Short Report The impact of wind speed measurement method on MRT and UTCI values ​​in limited air flow conditions within urban green areas. Katarzyna Lindner-Cendrowska, Magdalena Kuchcik This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-3380057/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 22 Jan, 2024 Read the published version in International Journal of Biometeorology → Version 1 posted 4 You are reading this latest preprint version Abstract Wind speed is an important variable in the assessment of thermal comfort. Different types of meteorological devices provide different accuracy of air velocity (va) measurements, what under limited air flow conditions, may result in an underestimation of actual thermal stress level. Simultaneous measurements on warm summer days, performed with a cup anemometer and hot-wire probe, prove that too high starting threshold of the first of these sensors can lead to underestimation of actual wind speed, and as a consequence can distort MRT (estimated with globe thermometer) and UTCI values ​​up to 10°C and 2°C respectively. wind speed MRT UTCI meteorological sensors urban green areas Figures Figure 1 Introduction Many urban areas, especially city parks covered with lush vegetation, are characterized by a significant reduction in wind speed (D’Isidoro et al., 2023 ; Kent et al., 2017 ). During field studies conducted in these areas, a variety of portable metrological devices is used to measure wind speed (Potchter et al., 2022 ), among which the most common are: cup or propeller anemometers, ultrasonic anemometers and hot-wire omnidirectional anemometers. ISO 7726 Standard (International Organization for Standardization, 1998 ) defines the specifications of meteorological instruments used for measuring physical quantities in thermal comfort and thermal stress studies. The required accuracy for air velocity measuring device in moderate environments approaching comfort conditions is ± (0.05 + 0.05 va) m/s, while in environments under greater thermal stress it is ± (0.1 + 0.05 va) m/s. Unfortunately, many previous studies have been conducted using instruments, that do not meet these requirements in very low wind speed conditions (Johansson et al., 2014 ). Although propeller or cup anemometers often provide satisfactory resolution, their starting threshold is too high (0.6-1 m/s) to record very low air velocity, and though they may underestimate the actual wind speed. Therefore the objective of this study was to analyse how the type of wind speed sensor may affect Mean Radiant Temperature (MRT) and Universal Thermal Climate Index (UTCI) values calculated on the basis of globe thermometer records. The analysis was carried out under weak air flow conditions, when starting threshold of sensors play an important role. Materials and methods The meteorological measurements were carried out within six green areas in Warsaw (Poland), during six warm, sunny days in August 2022, from 8:00 am to 6:00 pm (see ESM Section A1.). Measurements of all meteorological parameters were carried out at 1.1 m level above the ground, on grassy surfaces. Two types of sensors were used to measure wind speed: cup anemometer HOBO S-WSA-M003 and DeltaOhm omni-directional hot-wire probe AP3203 (see ESM Fig. A1.2). The starting threshold of the applied cup anemometer was 1 m/s, while for the hot-wire probe it was equal to the lower limit of the measurement range (0.02 m/s). The logging interval was set to 1 minute, but for further analysis 5-minute averages were used. Two commonly used black globe thermometers were used to determine the MRT: equipped with Ø15-cm standard copper sphere (SGT) and Ø4 cm acrylic sphere (AGT). MRT was calculated considering the measured globe temperature (Tg), air temperature (Ta) and wind speed (va), using original ISO-equation (Eq. 1 ) and assuming the emissivity of the black globe \(\epsilon\) = 0.95: $$MRT= \sqrt[4]{{(Tg+\text{273,15})}^{4}+\frac{{h}_{C}}{\epsilon \bullet \sigma }\bullet (Tg-Ta)}-\text{273,15} [^\circ C]$$ 1 In the case of natural convection, the convective heat transfer coefficient equals \({\text{h}}_{\text{C}}=\text{1,4}\bullet \left(\frac{Δ \text{T}}{\text{D}}\right)\) and under forced convection conditions \({\text{h}}_{\text{C}}=\text{6,3}\bullet \left(\frac{{\text{v}\text{a}}^{\text{0,6}}}{{\text{D}}^{\text{0,4}}}\right)\) , where D is the diameter of the globe in metres. Each time the one of the two hc coefficients that had the higher value was adopted to calculated MRT. UTCI was calculated using the regression polynomial, as described in the UTCI operational procedure (Bröde et al., 2012 ). Wind speed was conversed to required 10 m above ground height according to Eq. 2 . $${va}_{10m}=va\bullet LOG\left(10/0.01\right) / LOG\left(1.1/0.01\right)$$ 2 Results On measurement days, the air temperature was on average 25.8°C and ranged from 17.7 to 33.3°C. Total solar radiation was on average 470.1W/m 2 , with a maximum reaching 957.1 W/m 2 . 5-min averages of wind speed at 1.1 m above ground measured with cup anemometer and hot-wire probe were 0.23 and 1.04 m/s respectively, and 33% of the anemometer measurements equalled to 0 (see ESM Fig. A2.2). Regardless of the sensor type used for measuring globe temperature, the inclusion of wind speed values ​​measured with a cup anemometer resulted in lower MRT values. The higher the thermal radiation, the more important the method of measuring air flow was for the discrepancy in the MRT values. At MRT equal to 60°C, the underestimation effect due to using cup anemometer data was 12.0°C and 13.4​​°C for 15cm SGT and 4cm AGT respectively. However, in the case of determining UTCI, the influence of the wind speed measurement method was less evident. Even under very strong heat stress, when UTCI was 40°C, applying cup anemometer resulted in 2.8°C and 2.5°C lower values of the thermal stress index, for SGT and AGT accordingly (Fig. 1 ). Nevertheless, the observed relationships are limited only to low air flow conditions. For statistical comparisons of MRT and UTCI values between two methods used to measure wind speed see Section A3. in ESM (Table A3.1). Discussion and conclusions One of the most important parameters in determination thermal comfort level is air flow. It not only directly affects convective heat transfer from the human body and is therefore included as a component of many biometeorological indicators, but also affects the readings of instruments used to determine the amount of radiation absorbed by the organism. The method of estimating MRT with globe thermometers has been often criticized recently, as the air velocity strongly affects the instrument, causing a decrease of globe temperature with rising wind speed and greater fluctuation of its indications (Guo et al., 2020 ; Oliveira et al., 2019 ). At the same time, in many studies a little attention has been paid to the impact of various air velocity measurement methods on the accuracy of MRT and biometeorological indicators determination. In outdoor biometeorological studies one of the commonest devices used to control wind speed is two-dimensional cup anemometer (Johansson et al., 2014 ). Undeniably cup and propeller anemometers are cheap and easily accessible, but they have in general one major limitation: a threshold value below which wind speeds cannot be registered and their indications are sensible to air flow direction (International Organization for Standardization, 1998 ). An alternative is using much expensive high quality three-dimensional ultrasonic anemometers or omnidirectional hot-wire or hot-sphere anemometers. The latter are affordable and can measure very low wind speeds, but instead they have an upper wind speed limit, usually at 4–5 m/s, which also limits their appliance outdoors. Therefore, the type of anemometer should always be selected accordingly with the prevailing local wind conditions and required measurement accuracy in different applications. In the case of densely built-up or heavily vegetated areas, when the air flow is significantly impeded, the use of propeller or cup anemometers, which have high starting threshold, may lead to incorrect conclusions, especially under heat stress conditions. Our results suggest, that while MRT may be underestimated up to several degrees, with mean bias error reaching 10.4°C, for UTCI the MBE related to the use of cup anemometer does not exceed 2°C. Our study does not take into account the influence of air flow direction on the readings of globe thermometers, which was found in previous studies (Liu et al., 2022 ; Teitelbaum et al., 2022 ), and the results apply only to low wind conditions, below 2.5 m/s. What is more, due to the fact that our research was conducted only in the summer, further investigation is required to verify whether in cold stress conditions, type of instrument used to measure wind velocity determines similar discrepancies in the MRT and UTCI values. Declarations The authors declare no competing interests. Acknowledgements The project was supported by the National Science Centre, Poland, under research project no DEC-2021/05/X/ST10/00738. References Bröde P, Fiala D, Błażejczyk K, Holmér I, Jendritzky G, Kampmann B, Tinz B, Havenith G (2012) Deriving the operational procedure for the Universal Thermal Climate Index (UTCI). Int J Biometeorol 56(3):481–494. https://doi.org/10.1007/s00484-011-0454-1 D’Isidoro M, Mircea M, Borge R, Finardi S, Briganti G, Russo F, de la Paz D, Cremona G, Villani MG, Cappelletti A, Adani M, D’Elia I, Piersanti A, Sorrentino B, Petralia E, de Andrés JM, Narros A, Silibello C, Pepe N, …, Carlino G (2023) The Role of Vegetation on Urban Atmosphere of Three European Cities. Part 2: Evaluation of Vegetation Impact on Air Pollutant Concentrations and Depositions. Forests 14(6):1255. https://doi.org/10.3390/f14061255 Guo H, Aviv D, Loyola M, Teitelbaum E, Houchois N, Meggers F (2020) On the understanding of the mean radiant temperature within both the indoor and outdoor environment, a critical review. Renew Sustain Energy Rev 117:109207. https://doi.org/10.1016/j.rser.2019.06.014 International Organization for Standardization (1998) ISO 7726: Ergonomics of the Thermal Environment - Instruments for Measuring Physical Quantities Johansson E, Thorsson S, Emmanuel R, Krüger E (2014) Instruments and methods in outdoor thermal comfort studies - The need for standardization. Urban Clim 10:346–366. https://doi.org/10.1016/j.uclim.2013.12.002 Kent CW, Grimmond S, Gatey D (2017) Aerodynamic roughness parameters in cities: Inclusion of vegetation. J Wind Eng Ind Aerodyn 169(August):168–176. https://doi.org/10.1016/j.jweia.2017.07.016 Liu K, You W, Chen X, Liu W (2022) Study on the Influence of Globe Thermometer Method on the Accuracy of Calculating Outdoor Mean Radiant Temperature and Thermal Comfort. Atmosphere 13(5). https://doi.org/10.3390/atmos13050809 Oliveira AVM, Raimundo AM, Gaspar AR, Quintela DA (2019) Globe Temperature and Its Measurement: Requirements and Limitations. Annals of Work Exposures and Health 63(7):743–758. https://doi.org/10.1093/annweh/wxz042 Potchter O, Cohen P, Lin TP, Matzarakis A (2022) A systematic review advocating a framework and benchmarks for assessing outdoor human thermal perception. Science of the Total Environment , 833 (October 2021), 155128. https://doi.org/10.1016/j.scitotenv.2022.155128 Teitelbaum E, Alsaad H, Aviv D, Kim A, Voelker C, Meggers F, Pantelic J (2022) Addressing a systematic error correcting for free and mixed convection when measuring mean radiant temperature with globe thermometers. Sci Rep 12(1):1–18. https://doi.org/10.1038/s41598-022-10172-5 Supplementary Files ElectronicSupplementalMaterial.pdf Cite Share Download PDF Status: Published Journal Publication published 22 Jan, 2024 Read the published version in International Journal of Biometeorology → Version 1 posted Reviewers agreed at journal 04 Oct, 2023 Reviewers invited by journal 04 Oct, 2023 Editor assigned by journal 29 Sep, 2023 First submitted to journal 26 Sep, 2023 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-3380057","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Short Report","associatedPublications":[],"authors":[{"id":237769775,"identity":"98a1a2d2-f046-44e8-8bf9-6f311d3a0551","order_by":0,"name":"Katarzyna Lindner-Cendrowska","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA9ElEQVRIiWNgGAWjYBACCXbGBgYeIIMfzGWDiRfg0cIM1SLZhqLFAJ8WIAHSYnCMWC2SzcxtD97usMk3vt9j+LmizI7BnP3sAeYCPFqkmRnbDeeeSbPcdozHWPLMuWQGy568BOYZeLTIMTO2SfO2HTYwO8a7QbKxjZnB4ECOATMPYS3/DYzbeDf/bGyrZzA4/wa/FmmIlgMGBmy824C2HGYwuEHAFslmxjbJuW3JBhLH8r9ZNpw7zmM5443BYXx+kTje/kzibZudAX/zseSbDWXVcub8OYaPCypwa8EAYCcdJkEDAyQSmUnTMgpGwSgYBcMcAACIKUXZVMnyAwAAAABJRU5ErkJggg==","orcid":"https://orcid.org/0000-0002-8322-4653","institution":"Polska Akademia Nauk Instytut Geografii i Przestrzennego Zagospodarowania im Stanislawa Leszczyckiego","correspondingAuthor":true,"prefix":"","firstName":"Katarzyna","middleName":"","lastName":"Lindner-Cendrowska","suffix":""},{"id":237769776,"identity":"7c1f65cc-9254-46c2-8b47-923815884496","order_by":1,"name":"Magdalena Kuchcik","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Magdalena","middleName":"","lastName":"Kuchcik","suffix":""}],"badges":[],"createdAt":"2023-09-23 16:17:56","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-3380057/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-3380057/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s00484-024-02623-7","type":"published","date":"2024-01-22T15:10:35+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":44388029,"identity":"483339be-3594-4a8c-8bc5-8bd9e0df2abd","added_by":"auto","created_at":"2023-10-10 20:06:22","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":168352,"visible":true,"origin":"","legend":"\u003cp\u003eMean radiant temperature (MRT) and Universal Thermal Climate Index (UTCI) determined from 15 cm standard globe thermometer (SGT) and 4 cm acrylic globe thermometer (AGT) using wind speed values recorded by cup anemometer \u003cem\u003eversus\u003c/em\u003ehot-wire probe.\u003c/p\u003e","description":"","filename":"Fig1.png","url":"https://assets-eu.researchsquare.com/files/rs-3380057/v1/a57f148fafb44d549e619211.png"},{"id":50314035,"identity":"15ce1db7-6f67-4aee-911c-239089236a1e","added_by":"auto","created_at":"2024-01-29 15:28:47","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":327039,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-3380057/v1/4b4d51ec-9a93-427c-b36e-720e2ab3679b.pdf"},{"id":44388030,"identity":"c492bc56-e3de-4d60-a7bb-0b219c89afb7","added_by":"auto","created_at":"2023-10-10 20:06:22","extension":"pdf","order_by":5,"title":"","display":"","copyAsset":false,"role":"supplement","size":379085,"visible":true,"origin":"","legend":"","description":"","filename":"ElectronicSupplementalMaterial.pdf","url":"https://assets-eu.researchsquare.com/files/rs-3380057/v1/4589fd4b326f098d648cf302.pdf"}],"financialInterests":"","formattedTitle":"The impact of wind speed measurement method on MRT and UTCI values ​​in limited air flow conditions within urban green areas.","fulltext":[{"header":"Introduction","content":"\u003cp\u003eMany urban areas, especially city parks covered with lush vegetation, are characterized by a significant reduction in wind speed (D\u0026rsquo;Isidoro et al., \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; Kent et al., \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). During field studies conducted in these areas, a variety of portable metrological devices is used to measure wind speed (Potchter et al., \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2022\u003c/span\u003e), among which the most common are: cup or propeller anemometers, ultrasonic anemometers and hot-wire omnidirectional anemometers. ISO 7726 Standard (International Organization for Standardization, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e1998\u003c/span\u003e) defines the specifications of meteorological instruments used for measuring physical quantities in thermal comfort and thermal stress studies. The required accuracy for air velocity measuring device in moderate environments approaching comfort conditions is \u0026plusmn; (0.05\u0026thinsp;+\u0026thinsp;0.05 va) m/s, while in environments under greater thermal stress it is \u0026plusmn; (0.1\u0026thinsp;+\u0026thinsp;0.05 va) m/s. Unfortunately, many previous studies have been conducted using instruments, that do not meet these requirements in very low wind speed conditions (Johansson et al., \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). Although propeller or cup anemometers often provide satisfactory resolution, their starting threshold is too high (0.6-1 m/s) to record very low air velocity, and though they may underestimate the actual wind speed.\u003c/p\u003e \u003cp\u003eTherefore the objective of this study was to analyse how the type of wind speed sensor may affect Mean Radiant Temperature (MRT) and Universal Thermal Climate Index (UTCI) values calculated on the basis of globe thermometer records. The analysis was carried out under weak air flow conditions, when starting threshold of sensors play an important role.\u003c/p\u003e"},{"header":"Materials and methods","content":"\u003cp\u003eThe meteorological measurements were carried out within six green areas in Warsaw (Poland), during six warm, sunny days in August 2022, from 8:00 am to 6:00 pm (see ESM Section A1.). Measurements of all meteorological parameters were carried out at 1.1 m level above the ground, on grassy surfaces. Two types of sensors were used to measure wind speed: cup anemometer HOBO S-WSA-M003 and DeltaOhm omni-directional hot-wire probe AP3203 (see ESM Fig. A1.2). The starting threshold of the applied cup anemometer was 1 m/s, while for the hot-wire probe it was equal to the lower limit of the measurement range (0.02 m/s). The logging interval was set to 1 minute, but for further analysis 5-minute averages were used.\u003c/p\u003e\n\u003cp\u003eTwo commonly used black globe thermometers were used to determine the MRT: equipped with \u0026Oslash;15-cm standard copper sphere (SGT) and \u0026Oslash;4 cm acrylic sphere (AGT). MRT was calculated considering the measured globe temperature (Tg), air temperature (Ta) and wind speed (va), using original ISO-equation (Eq. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e) and assuming the emissivity of the black globe \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\epsilon\\)\u003c/span\u003e\u003c/span\u003e = 0.95:\u003c/p\u003e\n\u003cdiv id=\"Equ1\" class=\"Equation\"\u003e\n \u003cdiv class=\"mathdisplay\" id=\"FileID_Equ1\" name=\"EquationSource\"\u003e$$MRT= \\sqrt[4]{{(Tg+\\text{273,15})}^{4}+\\frac{{h}_{C}}{\\epsilon \\bullet \\sigma }\\bullet (Tg-Ta)}-\\text{273,15} [^\\circ C]$$\u003c/div\u003e\n \u003cdiv class=\"EquationNumber\"\u003e1\u003c/div\u003e\n\u003c/div\u003e\n\u003cp\u003eIn the case of natural convection, the convective heat transfer coefficient equals \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({\\text{h}}_{\\text{C}}=\\text{1,4}\\bullet \\left(\\frac{\u0026Delta; \\text{T}}{\\text{D}}\\right)\\)\u003c/span\u003e\u003c/span\u003e and under forced convection conditions \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({\\text{h}}_{\\text{C}}=\\text{6,3}\\bullet \\left(\\frac{{\\text{v}\\text{a}}^{\\text{0,6}}}{{\\text{D}}^{\\text{0,4}}}\\right)\\)\u003c/span\u003e\u003c/span\u003e, where D is the diameter of the globe in metres. Each time the one of the two hc coefficients that had the higher value was adopted to calculated MRT. UTCI was calculated using the regression polynomial, as described in the UTCI operational procedure (Br\u0026ouml;de et al., \u003cspan class=\"CitationRef\"\u003e2012\u003c/span\u003e). Wind speed was conversed to required 10 m above ground height according to Eq. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e\n\u003cdiv id=\"Equ2\" class=\"Equation\"\u003e\n \u003cdiv class=\"mathdisplay\" id=\"FileID_Equ2\" name=\"EquationSource\"\u003e$${va}_{10m}=va\\bullet LOG\\left(10/0.01\\right) / LOG\\left(1.1/0.01\\right)$$\u003c/div\u003e\n \u003cdiv class=\"EquationNumber\"\u003e2\u003c/div\u003e\n\u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003eOn measurement days, the air temperature was on average 25.8\u0026deg;C and ranged from 17.7 to 33.3\u0026deg;C. Total solar radiation was on average 470.1W/m\u003csup\u003e2\u003c/sup\u003e, with a maximum reaching 957.1 W/m\u003csup\u003e2\u003c/sup\u003e. 5-min averages of wind speed at 1.1 m above ground measured with cup anemometer and hot-wire probe were 0.23 and 1.04 m/s respectively, and 33% of the anemometer measurements equalled to 0 (see ESM Fig. A2.2).\u003c/p\u003e \u003cp\u003eRegardless of the sensor type used for measuring globe temperature, the inclusion of wind speed values ​​measured with a cup anemometer resulted in lower MRT values. The higher the thermal radiation, the more important the method of measuring air flow was for the discrepancy in the MRT values. At MRT equal to 60\u0026deg;C, the underestimation effect due to using cup anemometer data was 12.0\u0026deg;C and 13.4​​\u0026deg;C for 15cm SGT and 4cm AGT respectively. However, in the case of determining UTCI, the influence of the wind speed measurement method was less evident. Even under very strong heat stress, when UTCI was 40\u0026deg;C, applying cup anemometer resulted in 2.8\u0026deg;C and 2.5\u0026deg;C lower values of the thermal stress index, for SGT and AGT accordingly (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Nevertheless, the observed relationships are limited only to low air flow conditions. For statistical comparisons of MRT and UTCI values between two methods used to measure wind speed see Section A3. in ESM (Table A3.1).\u003c/p\u003e"},{"header":"Discussion and conclusions","content":"\u003cp\u003eOne of the most important parameters in determination thermal comfort level is air flow. It not only directly affects convective heat transfer from the human body and is therefore included as a component of many biometeorological indicators, but also affects the readings of instruments used to determine the amount of radiation absorbed by the organism. The method of estimating MRT with globe thermometers has been often criticized recently, as the air velocity strongly affects the instrument, causing a decrease of globe temperature with rising wind speed and greater fluctuation of its indications (Guo et al., \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Oliveira et al., \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). At the same time, in many studies a little attention has been paid to the impact of various air velocity measurement methods on the accuracy of MRT and biometeorological indicators determination.\u003c/p\u003e \u003cp\u003eIn outdoor biometeorological studies one of the commonest devices used to control wind speed is two-dimensional cup anemometer (Johansson et al., \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). Undeniably cup and propeller anemometers are cheap and easily accessible, but they have in general one major limitation: a threshold value below which wind speeds cannot be registered and their indications are sensible to air flow direction (International Organization for Standardization, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e1998\u003c/span\u003e). An alternative is using much expensive high quality three-dimensional ultrasonic anemometers or omnidirectional hot-wire or hot-sphere anemometers. The latter are affordable and can measure very low wind speeds, but instead they have an upper wind speed limit, usually at 4\u0026ndash;5 m/s, which also limits their appliance outdoors. Therefore, the type of anemometer should always be selected accordingly with the prevailing local wind conditions and required measurement accuracy in different applications. In the case of densely built-up or heavily vegetated areas, when the air flow is significantly impeded, the use of propeller or cup anemometers, which have high starting threshold, may lead to incorrect conclusions, especially under heat stress conditions. Our results suggest, that while MRT may be underestimated up to several degrees, with mean bias error reaching 10.4\u0026deg;C, for UTCI the MBE related to the use of cup anemometer does not exceed 2\u0026deg;C.\u003c/p\u003e \u003cp\u003eOur study does not take into account the influence of air flow direction on the readings of globe thermometers, which was found in previous studies (Liu et al., \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Teitelbaum et al., \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2022\u003c/span\u003e), and the results apply only to low wind conditions, below 2.5 m/s. What is more, due to the fact that our research was conducted only in the summer, further investigation is required to verify whether in cold stress conditions, type of instrument used to measure wind velocity determines similar discrepancies in the MRT and UTCI values.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe project was supported by the National Science Centre, Poland, under research project no DEC-2021/05/X/ST10/00738.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eBr\u0026ouml;de P, Fiala D, Błażejczyk K, Holm\u0026eacute;r I, Jendritzky G, Kampmann B, Tinz B, Havenith G (2012) Deriving the operational procedure for the Universal Thermal Climate Index (UTCI). 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Sci Rep 12(1):1\u0026ndash;18. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1038/s41598-022-10172-5\u003c/span\u003e\u003cspan address=\"10.1038/s41598-022-10172-5\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":true,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"international-journal-of-biometeorology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ijbm","sideBox":"Learn more about [International Journal of Biometeorology](http://link.springer.com/journal/484)","snPcode":"484","submissionUrl":"https://www.editorialmanager.com/ijbm/default2.aspx","title":"International Journal of Biometeorology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"wind speed, MRT, UTCI, meteorological sensors, urban green areas","lastPublishedDoi":"10.21203/rs.3.rs-3380057/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-3380057/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eWind speed is an important variable in the assessment of thermal comfort. Different types of meteorological devices provide different accuracy of air velocity (va) measurements, what under limited air flow conditions, may result in an underestimation of actual thermal stress level. Simultaneous measurements on warm summer days, performed with a cup anemometer and hot-wire probe, prove that too high starting threshold of the first of these sensors can lead to underestimation of actual wind speed, and as a consequence can distort MRT (estimated with globe thermometer) and UTCI values ​​up to 10°C and 2°C respectively.\u003c/p\u003e","manuscriptTitle":"The impact of wind speed measurement method on MRT and UTCI values ​​in limited air flow conditions within urban green areas.","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2023-10-10 20:06:17","doi":"10.21203/rs.3.rs-3380057/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewerAgreed","content":"","date":"2023-10-04T08:41:27+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2023-10-04T07:39:58+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2023-09-29T18:40:35+00:00","index":"","fulltext":""},{"type":"submitted","content":"International Journal of Biometeorology","date":"2023-09-26T06:57:58+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"international-journal-of-biometeorology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ijbm","sideBox":"Learn more about [International Journal of Biometeorology](http://link.springer.com/journal/484)","snPcode":"484","submissionUrl":"https://www.editorialmanager.com/ijbm/default2.aspx","title":"International Journal of Biometeorology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"59862cb5-a1c4-442f-a738-5979c3724850","owner":[],"postedDate":"October 10th, 2023","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2024-01-29T15:25:38+00:00","versionOfRecord":{"articleIdentity":"rs-3380057","link":"https://doi.org/10.1007/s00484-024-02623-7","journal":{"identity":"international-journal-of-biometeorology","isVorOnly":false,"title":"International Journal of Biometeorology"},"publishedOn":"2024-01-22 15:10:35","publishedOnDateReadable":"January 22nd, 2024"},"versionCreatedAt":"2023-10-10 20:06:17","video":"","vorDoi":"10.1007/s00484-024-02623-7","vorDoiUrl":"https://doi.org/10.1007/s00484-024-02623-7","workflowStages":[]},"version":"v1","identity":"rs-3380057","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-3380057","identity":"rs-3380057","version":["v1"]},"buildId":"_2-kVJe1T_tPrBINL-cwx","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}