The role of trees in enhancing outdoor thermal comfort during warm season in a sub-humid climate. Case: Souk Ahras City

Fatma Khelifa, Aissa Mahimoud, Djamel Alkama, Abdelhakim Hanafi


Enhancing the quality of life for people in urban areas necessitates focusing on outdoor thermal comfort OTC. This study examines the role and impact of urban vegetation, particularly trees, in improving the meteorological conditions that characterize the urban microclimate in order to enhance OTC, focusing on two public spaces in Souk Ahras city, characterised by in situ measurement campaigns and modelling during hot summer day. In situ campaigns were carried out to measure climatic data (air temperature, relative humidity and wind speed), and to collect data on vegetation (trees) and building geometry, which were used in numerical modelling to calculate the various thermal indices: SVF, Tmrt, PET and OUT_SET using the Rayman microclimatic model. The results show that the trees at each intervention site can reduce the average daily air temperature of 0.376◦C to 1.04◦C and an enhancement of thermal comfort in terms of average radiant temperature Tmrt of 2. 08° ◦C to 5.85◦C and equivalent physiological temperature PET of 1.91 ◦C to 3.84◦C and standard equivalent temperature OUT_SET of 1.72◦C to 2.86◦C. in the knowledge that trees also help to reduce the Skye view factor, an essential geometric measure for assessing the thermal environment, which proves that the effect of shading and evapotranspiration provided by trees mainly contribute to enhancing outdoor thermal comfort during the warm season.

Keywords: heat stress, trees, outdoor thermal comfort, thermal indices

© 2023 Serbian Geographical Society, Belgrade, Serbia.

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Serbia.


Ahmadi Venhari, A., Tenpierik, M., & Taleghani, M. (2019). The role of sky view factor and urban street greenery in human thermal comfort and heat stress in a desert climate. Journal of Arid Environments, 166, 68‑76.

Cheung, P. K. (2018). Comparing the cooling effects of a tree and a concrete shelter using PET and UTCI. Building and Environment, 130, 49-61.

Dissanayake, C., & Weerasinghe, G. (2022). Influence of Urban Design Interventions on Outdoor Thermal Comfort in Tropical Cities; a Review. Rajarata University Journal, 7(1), 49-61.

De Abreu-Harbich, L. V., Labaki, L. C., & Matzarakis, A. (2015). Effect of tree planting design and tree species on human thermal comfort in the tropics. Landscape and Urban Planning, 138, 99-109.

Fröhlich, D., & Matzarakis, A. (2020). Calculating human thermal comfort and thermal stress in the PALM model system 6.0. Geoscientific Model Development, 13(7), 3055‑3065.

Gatto, E., Ippolito, F., Rispoli, G., Carlo, O. S., Santiago, J. L., Aarrevaara, E., Emmanuel, R., & Buccolieri, R. (2021). Analysis of Urban Greening Scenarios for Improving Outdoor Thermal Comfort in Neighbourhoods of Lecce (Southern Italy). Climate, 9(7), 116.

Heng, S. L., & Chow, W. T. L. (2019). How ‘hot’ is too hot? Evaluating acceptable outdoor thermal comfort ranges in an equatorial urban park. International Journal of Biometeorology, 63(6), 801‑816.

Höppe, P. (1999). The physiological equivalent temperature—A universal index for the biometeorological assessment of the thermal environment. International Journal of Biometeorology, 43(2), 71‑75.

Houamel, S. (2018). Les steppes d’armoise blanche (Artemisia herba-alba Asso) dans l’Est Algérien: Répartition actuelle, biodiversité, dynamique et conditions de durabilité [Thèse de Doctorat, Université Mohamed Kheider- Biskra].

Ji, W., Zhu, Y., Du, H., Cao, B., Lian, Z., Geng, Y., Liu, S., Xiong, J., & Yang, C. (2022). Interpretation of standard effective temperature (SET) and explorations on its modification and development. Building and Environment, 210, Article 108714.

Kumar, P., & Sharma, A. (2020). Study on importance, procedure, and scope of outdoor thermal comfort – A review. Sustainable Cities and Society, 61, Article 102297.

Lin, T.-P., Matzarakis, A., & Hwang, R.-L. (2010). Shading effect on long-term outdoor thermal comfort. Building and Environment, 45(1), 213‑221.

Liu, Z., Cheng, W., Jim, C. Y., Morakinyo, T. E., Shi, Y., & Ng, E. (2021). Heat mitigation benefits of urban green and blue infrastructures: A systematic review of modeling techniques, validation and scenario simulation in ENVI-met V4. Building and Environment, 200, Article 107939.

Matzarakis, A., Rutz, F., & Mayer, H. (2010). Modelling radiation fluxes in simple and complex environments: Basics of the RayMan model. International Journal of Biometeorology, 54(2), 131‑139.

Meili, N. (2021). Vegetation cover and plant-trait effects on outdoor thermal comfort in a tropical city. Building and Environment, 195, Article 107733.

Morakinyo, T. E., Dahanayake, K. W. D. Kalani. C., Adegun, O. B., & Balogun, A. A. (2016). Modelling the effect of tree-shading on summer indoor and outdoor thermal condition of two similar buildings in a Nigerian university. Energy and Buildings, 130, 721‑732.

Nazarian, N., Fan, J., Sin, T., Norford, L., & Kleissl, J. (2017). Predicting outdoor thermal comfort in urban environments: A 3D numerical model for standard effective temperature. Urban Climate, 20, 251‑267.

Teshnehdel, S., Akbari, H., Di Giuseppe, E., & Brown, R. D. (2020). Effect of tree cover and tree species on microclimate and pedestrian comfort in a residential district in Iran. Building and Environment, 178, Article 106899.

Xiao, J., & Yuizono, T. (2022). Climate-adaptive landscape design: Microclimate and thermal comfort regulation of station square in the Hokuriku Region, Japan. Building and Environment, 212, Article 108813.

Zhang, J. (2019). The impact of sky view factor on thermal environments in urban parks in a subtropical coastal city of Australia. Urban Forestry & Urban Greening, 46, Article 126422.

Zhang, J., Khoshbakht, M., Liu, J., Gou, Z., Xiong, J., & Jiang, M. (2022). A clustering review of vegetation-indicating parameters in urban thermal environment studies towards various factors. Journal of Thermal Biology, 110, Article 103340.

Zheng, S., Guldmann, J.-M., Liu, Z., & Zhao, L. (2018). Influence of trees on the outdoor thermal environment in subtropical areas : An experimental study in Guangzhou, China. Sustainable Cities and Society, 42, 482‑497.

Zhimin Zheng, Yuchun Zhang, Yudong Mao, Yanping Yang, Chuhao Fu, & Zhaosong Fang. (2021). Analysis of SET* and PMV to evaluate thermal comfort in prefab construction site offices:Case study in South China. Case Studies in Thermal Engineering, 26.


  • There are currently no refbacks.