Combining interdisciplinary field measurements and ENVI-met simulations for comparative assessment of outdoor human thermal comfort across local climate zones

Gregorčič, Tim (author), Ogrin, Matej (author), Repe, Blaž (author), Savić, Stevan (author)

Owing to the specific thermal conditions of the urban environment, such as a high proportion of impervious surfaces, low tree cover, high building density, and low surface albedo, residents in these areas experience altered outdoor thermal comfort (OTC). Although these conditions generally contribute to elevated heat stress during hot summer days, this phenomenon varies spatially and temporally. Numerous studies have examined OTC indices across different cities using various modelling techniques; however, the preparation of spatial input data is often insufficiently addressed. Therefore, the study aims to quantify and assess OTC across selected Local Climate Zones (LCZs) in Ljubljana, as well as the effect of existing tree shading on OTC improvement, by advancing a modelling workflow that explicitly incorporates detailed field-derived urban soil characteristics into ENVI-met simulations. This was achieved through interdisciplinary field and laboratory measurements combined with urban microclimatic modelling. The fieldwork included micrometeorological measurements, soil sampling, surface albedo measurements, and green infrastructure mapping. The results revealed statistically significant differences in Universal Thermal Climate Index (UTCI) and Physiological Equivalent Temperature (PET) indices between 13:00 and 15:00 local time across the LCZs. LCZ A exhibited the lowest levels of heat stress, whereas LCZ 8 experienced the highest. The average differences in UTCI and PET between these two zones were 9.23 ◦C and 12.44 ◦C, respectively. Further analysis demonstrated that existing tree shade significantly improved OTC. Across all LCZs, the average thermal comfort improved by 5.67 ◦C (UTCI) and 8.43 ◦C (PET) under tree shade compared to areas exposed to direct solar radiation.

• Language: English
• Keywords: urban climate, heat stress, universal thermal climate index (UTCI), physiological equivalent temperature (PET), soils, local climate zones (LCZ), green infrastructure, climatogeography, outdoor human thermal comfort
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FF - Faculty of Arts
• Publication status: Published
• Publication version: Version of Record
• Publication date: 15.05.2026
• Year: 2026
• Number of pages: 16 str.
• Numbering: Vol. 142, [article no.] 107304
• PID: 20.500.12556/RUL-188357
• UDC: 911.375:551.584.3
• ISSN on article: 2210-6715
• DOI: 10.1016/j.scs.2026.107304
• COBISS.SI-ID: 272851971
• Publication date in RUL: 21.09.2026

Record is a part of a journal

• Title: Sustainable cities and society
• Publisher: Elsevier
• ISSN: 2210-6715
• COBISS.SI-ID: 16177461

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Secondary language

• Language: Slovenian
• Keywords: mestna klima, topolotni stres, univerzalni toplotni podnebni indeks, fiziološka ekvivalentna temperatura, prsti, lokalne podnebne cone, zelena infrastruktura, klimatogeografija, zunanje toplotno ugodje