Investigating outdoor thermal comfort variations across Local Climate Zones in Nagpur, India, using ENVI-met

Increasing temperatures are exacerbating the urban heat island effect within urban areas. As thermal stress rises in these environments, evaluating the variation in thermal comfort across the city is crucial for designing thermally comfortable spaces. Nagpur, a centrally located city in India experiences extreme thermal stress during the summer. The present study focuses on assessing the variation in thermal comfort using indices such as air temperature (AT), physiological equivalent temperature (PET), and universal thermal comfort index (UTCI) which acknowledge energy balance in the human body and its relationship with the outdoor environment. These indices are calculated across ten areas in the city, identified by Local Climate Zone (LCZ) using ENVI-met. The 24-h simulations revealed that open and vegetated urban areas (LCZ 6, 6B & A) present low heat stress during 14:00-15:00 and 03:00-04:00. However, sparsely built areas (LCZ 9 & 93) experience extreme thermal stress during daytime and moderate stress during nighttime. Densely built areas (LCZ 3 & 3F) present moderate thermal stress during the daytime and the highest during nighttime. Further, PET and UTCI percentile assessments revealed that sparsely built areas experience both extreme and neutral thermal stress. Compact areas stay moderately warm during nighttime. Vegetated areas experience moderately high thermal stress during the daytime and neutral to warm thermal stress during nighttime. The study highlights the need for more emphasis on nighttime thermal stress using ENVI-met to assess thermal conditions across various urban settings. This will contribute to a better understanding of climates and locations experiencing extreme thermal stress.