Enhancing the microclimate of outdoor campus spaces in hot humid climates: the example of the University of Sharjah

Abstract

This study aims to assess the microclimatic differences between multiple urban areas in a university campus and to examine the impact of adding trees to these different areas at the University of Sharjah's campus in the United Arab Emirates (UAE). Five locations were chosen and compared to each other by first collecting weather data for 24 h on November 25–26, 2024, a month characterized by a rise in student activities and a transition between the hotter and the cooler seasons in the UAE. These measurements are used to calibrate subsequent Envi-met simulations. Tree types that are native or adapted to UAE’s hot climate are added to all sites under study, and the microclimatic conditions before and after their addition were compared for each site individually and collectively. According to the study's results, variations exist across the five studied campus sites, with open spaces experiencing higher thermal stress due to direct solar exposure and insufficient shading. Courtyards, or areas that resemble courtyards, exhibit better thermal conditions due to self-shading effects. While air temperature across the sites fell by less than 1 °C, adding trees that offered shade led to MRT decreases of up to 41%. These findings emphasize the role of vegetation in improving the outdoor microclimate by enhancing shading.

Keywords

University campus / Outdoor microclimate / Vegetation intervention / Urban design / Hot-humid climate / University of Sharjah

References

[1] Al-KhawajaS, AsfourOS. The impact of COVID-19 on the importance and use of public parks in Saudi Arabia. Ain Shams Engineering Journal, 2024, 15. 102286

[2] Al-Sallal, K.A., AbouElhamd, A.R., 2018. Natural Ventilation in Hot Seaside Urban Environments. pp. 27–41. https://doi.org/10.1007/978-3-319-67949-5_3

[3] Andrés-Anaya, P., Sánchez-Aparicio, M., del Pozo, S., Lagüela, S., 2021. Correlation of Land Surface Temperature with IR Albedo for the Analysis of Urban Heat Island, in: The 16th International Workshop on Advanced Infrared Technology & Applications. MDPI, Basel Switzerland, p. 9. https://doi.org/10.3390/engproc2021008009

[4] AzcarateI, AceroJÁ, GarmendiaL, RojíE. Tree layout methodology for shading pedestrian zones: Thermal comfort study in Bilbao (Northern Iberian Peninsula). Sustainable Cities and Society, 2021, 72. 102996

[5] BarutiMM, YahiaMW, JohanssonE. Spatial and temporal variations of microclimate and outdoor thermal comfort in informal settlements of warm humid Dar es Salaam. Tanzania. Heliyon, 2024, 10. e23160

[6] BherwaniH, AnjumS, GuptaA, SinghA, KumarR. Establishing influence of morphological aspects on microclimatic conditions through GIS-assisted mathematical modeling and field observations. Environment, Development and Sustainability, 2021, 23: 15857-15880.

[7] BowlerDE, Buyung-AliL, KnightTM, PullinAS. Urban greening to cool towns and cities: A systematic review of the empirical evidence. Landscape and Urban Planning, 2010, 97: 147-155.

[8] CheungPK, JimCY. Comparing the cooling effects of a tree and a concrete shelter using PET and UTCI. Building and Environment, 2018, 130: 49-61.

[9] Cheung, P.K., Jim, C.Y., 2019. Effects of urban and landscape elements on air temperature in a high-density subtropical city. Build Environ 164. https://doi.org/10.1016/j.buildenv.2019.106362

[10] Deng, L., Jia, X., Wang, W., Hussain, S.A., 2022. Revealing Impacts of Trees on Modeling Microclimate Behavior in Spaces between Buildings through Simulation Monitoring. Buildings 12(8), Article 1168. https://doi.org/10.3390/buildings12081168.

[11] DetommasoM, CostanzoV, NoceraF. Application of weather data morphing for calibration of urban ENVI-met microclimate models. Results and Critical Issues. Urban Clim, 2021, 38. 100895

[12] Diz-MelladoE, López-CabezaVP, Rivera-GómezC, NaboniE, Galán-MarínC. Optimizing a courtyard microclimate with adaptable shading and evaporative cooling in a hot mediterranean climate. Journal of Building Engineering, 2024, 88. 109167

[13] ENVI-met, 2024. Urban cooling and climate adaptation software [WWW Document]. ENVI-met GmbH. URL https://envi-met.com/microclimate-simulation-software/ (accessed 12.8.24).

[14] FanC, ZouB, LiJ, WangM, LiaoY, ZhouX. Exploring the relationship between air temperature and urban morphology factors using machine learning under local climate zones. Case Studies in Thermal Engineering, 2024, 55. 104151

[15] Feng, X., Wen, H., He, M., Xiao, Y., 2023. Microclimate effects and influential mechanisms of four urban tree species underneath the canopy in hot and humid areas. Front Environ Sci 11. https://doi.org/10.3389/fenvs.2023.1108002

[16] GiddingsB, CharltonJ, HorneM. Public squares in European city centres. URBAN DESIGN International, 2011, 16: 202-212.

[17] Gong, W., Ye, X., Wu, K., Jamonnak, S., Zhang, W., Yang, Y., Huang, X., 2025. Integrating Spatiotemporal Vision Transformer into Digital Twins for High-Resolution Heat Stress Forecasting in Campus Environments. arXiv. https://doi.org/10.48550/arXiv.2502.09657.

[18] GuoF, GuoR, ZhangH, DongJ, ZhaoJ. A canopy shading-based approach to heat exposure risk mitigation in small squares. Urban Clim, 2023, 49. 101495

[19] HamdanDMA, de OliveiraFL. The impact of urban design elements on microclimate in hot arid climatic conditions: Al Ain City, UAE. Energy Build, 2019, 200: 86-103.

[20] HuangX, SongJ. Urban moisture and dry islands: Spatiotemporal variation patterns and mechanisms of urban air humidity changes across the globe. Environmental Research Letters, 2023, 18. 103003

[21] IbrahimI, Al BadriN, MushtahaE, OmarO. Evaluating the Impacts of Courtyards on Educational Buildings, Case Study in the University of Sharjah. Sustainability, 2021, 14141.

[22] Ivanko, I.A., Kabar, A.M., Holoborodko, K.K., Didur, O.O., 2024. Microclimatic effects of introduced tree plantings in urban environment. Ecology and Noospherology35, 22–27. https://doi.org/10.15421/032403

[23] Kestrel Instruments, 2024. Kestrel 5400 WBGT Heat Stress Tracker (HST) & Weather Meter [WWW Document]. Kestrel Instruments. URL https://kestrelinstruments.com/kestrel-5400-heat-stress-tracker?srsltid=AfmBOooemSEl0pywE6TUJ84-iOYfHe294iZZ3s0c9PCEfNuZzysC2Iqi (accessed 12.8.24).

[24] KhelifaF, MahimoudA, AlkamaD, HanafiA. The role of trees in enhancing outdoor thermal comfort during warm season in a sub-humid climate. Case: Souk Ahras city. Glasnik Srpskog Geografskog Drustva, 2024, 104: 239-254.

[25] LachapelleJA, Scott KrayenhoffE, MiddelA, CoseoP, WarlandJ. Maximizing the pedestrian radiative cooling benefit per street tree. Landscape and Urban Planning, 2023, 230. 104608

[26] Lakes Software, 2024. WRplot View [WWW Document]. URL https://www.weblakes.com/software/freeware/wrplot-view (accessed 1.21.24).

[27] Li, J., Zhai, Z., Ding, Y., Li, H., Deng, Y., Chen, S., Ye, L., 2023. Effect of optimal allocation of urban trees on the outdoor thermal environment in hot and humid areas: A case study of a university campus in Guangzhou, China. Energy Build 300. https://doi.org/10.1016/j.enbuild.2023.113640

[28] LiQi, LiQ, LuX, LiuY. Numerical simulation of the effect of street trees on outdoor mean radiant temperature through decomposing pedestrian experienced thermal radiation: A case study in Guangzhou. China. Urban for Urban Green, 2024, 91. 128189

[29] LiangC, HuangY, ShiY, WuD, ChangQ, DuB, GuoX, KuangD, WuZ, ZhaoC, TangX, QiuJ, HeY. Evaluation of the Humidification Effect of Street Trees Based on All-Inorganic Lead-Free K ₂ CuBr ₃ Humidity Sensors. ACS Applied Electronic Materials, 2022, 4: 1592-1602.

[30] LindbergF, OnomuraS, GrimmondCSB. Influence of ground surface characteristics on the mean radiant temperature in urban areas. International Journal of Biometeorology, 2016, 60: 1439-1452.

[31] Manneh, A., Taleb, H., 2017. Vegetation Impact on Microclimate in Hot Climate Zones. https://doi.org/10.11159/icesdp17.180

[32] MortojaMdG, YigitcanlarT, MayereS. What is the most suitable methodological approach to demarcate peri-urban areas? A systematic review of the literature. Land Use Policy, 2020, 95. 104601

[33] PalazzoE, RaniWNMWM. Regenerating Urban Areas Through Climate Sensitive Urban Design. Advanced Science Letters, 2017, 23: 6394-6398.

[34] PicotX. Thermal comfort in urban spaces: Impact of vegetation growth. Energy Build, 2004, 36: 329-334.

[35] RenX, ZhangG, ChenZ, ZhuJ. The Influence of Wind-Induced Response in Urban Trees on the Surrounding Flow Field. Atmosphere (Basel), 2023, 141010.

[36] RenZ, ZhaoH, FuY, XiaoL, DongY. Effects of urban street trees on human thermal comfort and physiological indices: A case study in Changchun city, China. J for Res (Harbin), 2022, 33: 911-922.

[37] RuiL, BuccolieriR, GaoZ, DingW, ShenJ. The Impact of Green Space Layouts on Microclimate and Air Quality in Residential Districts of Nanjing. China. Forests, 2018, 9224.

[38] Salameh, M., Elkhazindar, A., Touqan, B., 2023. The effect of building height on thermal properties and comfort of a housing project in the hot arid climate of the UAE. Front Built Environ 9. https://doi.org/10.3389/fbuil.2023.1174147

[39] ShaamalaA, YigitcanlarT, NiliA, NyandegaD. Algorithmic green infrastructure optimisation: Review of artificial intelligence driven approaches for tackling climate change. Sustainable Cities and Society, 2024, 101. 105182

[40] Shashua-BarL, PearlmutterD, ErellE. The cooling efficiency of urban landscape strategies in a hot dry climate. Landscape and Urban Planning, 2009, 92: 179-186.

[41] ShihW-M, LinT-P, TanN-X, LiuM-H. Long-term perceptions of outdoor thermal environments in an elementary school in a hot-humid climate. International Journal of Biometeorology, 2017, 61: 1657-1666.

[42] ShivannaKR. Climate change and its impact on biodiversity and human welfare. Proceedings of the Indian National Science Academy, 2022, 88: 160-171.

[43] SonettiG, LombardiP, ChelleriL. True Green and Sustainable University Campuses?. Toward a Clusters Approach. Sustainability, 2016, 883.

[44] SpoonerD. Enhancing Campus Sustainability Through SITES and Socially Equitable Design. Planning for Higher Education Journal, 2014, 42: 30-31

[45] SrivanitM, HokaoK. Evaluating the cooling effects of greening for improving the outdoor thermal environment at an institutional campus in the summer. Building and Environment, 2013, 66: 158-172.

[46] SunH, Jimenez-BescosC, MohammadiM, ZhongF, CalautitJK. Numerical Investigation of the Influence of Vegetation on the Aero-Thermal Performance of Buildings with Courtyards in Hot Climates. Energies (Basel), 2021, 145388.

[47] Suwanmanee, N., Kronprasert, N., Sutheerakul, C., Arunotayanun, K., Rinchumphu, D., 2024. Investigation of Outdoor Thermal Comfort for Campus Pedestrian Walkways in Thailand. Sustainability (Switzerland) 16. https://doi.org/10.3390/su16020657

[48] Tabatabaei, S.S., Fayaz, R., 2023. The effect of facade materials and coatings on urban heat island mitigation and outdoor thermal comfort in hot semi-arid climate. Build Environ 243. https://doi.org/10.1016/j.buildenv.2023.110701

[49] Tarsheed, Abu Dhabi Distribution CO., Al Ain Distribution Company, 2021. An initiative by GARDENING IN ABU DHABI. Abu Dhabi.

[50] TomasiM, NikolopoulouM, GiridharanR, LöveM. A design workflow for effective solar shading of pedestrian paths. Building and Environment, 2024, 261. 111718

[51] WallenbergN, LindbergF, RaynerD. Locating trees to mitigate outdoor radiant load of humans in urban areas using a metaheuristic hill-climbing algorithm – introducing TreePlanter v1.0. Geosci Model Dev, 2022, 15: 1107-1128.

[52] WangY, AkbariH. The effects of street tree planting on Urban Heat Island mitigation in Montreal. Sustainable Cities and Society, 2016, 27: 122-128.

[53] WongNH, TanCL, KolokotsaDD, TakebayashiH. Greenery as a mitigation and adaptation strategy to urban heat. Nat Rev Earth Environ, 2021, 2: 166-181.

[54] YahiaMW, JohanssonE. Landscape interventions in improving thermal comfort in the hot dry city of Damascus, Syria—The example of residential spaces with detached buildings. Landscape and Urban Planning, 2014, 125: 1-16.

[55] Yan, J., Sun, N., Zheng, J., Zhang, Y., Yin, S., 2024. Uneven PM2.5 dispersion pattern across an open-road vegetation barrier: Effects of planting combination and wind condition. Science of The Total Environment 917, 170479. https://doi.org/10.1016/j.scitotenv.2024.170479

[56] Yang, F., Chen, L., 2020. Cooling Effects of Urban Greenery at Three Scales. pp. 163–183. https://doi.org/10.1007/978-981-15-1714-3_7

[57] Yang, J., Zhao, Y., Zou, Y., Xia, D., Lou, S., Guo, T., Zhong, Z., 2022. Improving the Thermal Comfort of an Open Space via Landscape Design: A Case Study in Hot and Humid Areas. Atmosphere (Basel) 13. https://doi.org/10.3390/atmos13101604

[58] Yuan, C., 2018. A Semi-Empirical Model for Urban Trees Effects on the Wind Environment. pp. 141–161. https://doi.org/10.1007/978-981-10-5451-8_8

[59] Zeeshan, M., Ali, Z., Ranjha, Q.A., 2023. Green Infrastructure with Actual Canopy Parameterization: A Simulation Study for Heat Stress Mitigation in a Hot-Humid Urban Environment. Arboric Urban For 49, 247–267. https://doi.org/10.48044/jauf.2023.016

[60] ZhangY, DaiM. Analysis of the Cooling and Humidification Effect of Multi-Layered Vegetation Communities in Urban Parks and Its Impact. Atmosphere (Basel), 2022, 132045.

[61] ZhengS, HeC, XuH, GuldmannJ-M, LiuX. Heat Mitigation Benefits of Street Tree Species during Transition Seasons in Hot and Humid Areas: A Case Study in Guangzhou. Forests, 2024, 151459.

[62] ZhengS, ZhaoL, LiQ. Numerical simulation of the impact of different vegetation species on the outdoor thermal environment. Urban for Urban Green, 2016, 18: 138-150.

RIGHTS & PERMISSIONS

The Author(s)