Outdoor thermal sensation scale through biometeorological assessment for semi-arid climate

Extreme temperatures in urban areas cause discomfort leading to a rise in health risks, like heat-related mortality (hyperthermia). It is, hence, important to have a comfortable thermal environment. Assessing outdoor thermal comfort is challenging and complicated due to its dependencies on biometeorological and psychological factors. This study investigates the outdoor thermal comfort in Ahmedabad, a city with semi-arid climate in India through biometeorological measurements and thermal comfort surveys. The study carried out thermal comfort surveys of 1620 subjects spread across the city in 2022-23 covering all the seasons. The temperature and relative humidity were in the range of 21.6 °C to 44.9 °C and 8 to 86% respectively. About 43% of the subjects felt thermally comfortable during the survey. Based on the survey results, the annual neutral Physiological Equivalent Temperature (PET) obtained was 27.5 °C, and the comfortable PET range was between 21.1 °C and 33.9 °C which covers a wide range. Neutral PET for summer and winter seasons obtained were similar, which indicates winters are getting milder and people of Ahmedabad are getting more adaptive towards warmer temperature. These results hold special significance as there is limited research on outdoor thermal comfort in such climate zone of India.