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

• ENVI-met parameterisation incorporating field- and laboratory-derived soil data advances OTC modelling beyond standard database inputs. • ENVI-met modelling reveals significant OTC differences across LCZs of Ljubljana. • Mean OTC varies by up to 12.44 °C between LCZs on hot summer days. • Tree shade reduces heat stress by up to 8.43 °C in Ljubljana's urban landscape. 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.