Assessment of Universal Thermal Comfort Index (UTCI) using the WRF-UCM model over a Metropolitan City in India

Abstract

Rapid urbanization leads to an increase in urban air temperature, considerably affecting health, comfort and the quality of life in urban spaces. The accurate assessment of outdoor thermal comfort is crucial for urban health. In the present study, a high-resolution mesoscale model coupled with a layer Urban Canopy Model (WRF-UCM) is implemented over the city of Hyderabad (17.3850° N, 78.4867° E) to simulate urban meteorological conditions during the summer and winter period of 2009 and 2019. The universal thermal climate index (UTCI) has been estimated using the model-derived atmospheric variables and a human biometeorology parameter to assess the linkages between the outdoor environment and thermal comfort. Results revealed that during summer, the city experiences nearly 10 hours of extreme to strong thermal stress, whereas moderate thermal and slight cold stress are experienced during winter. The urban area in Hyderabad expanded from 5–15% during the study period, leading to a 3℃ (1.5 ℃) increase in land surface temperature and a 1 to 1.5 ℃ (0.5 to 1 ℃ ) rise in air temperature at 2m height and UTCI during summer (winter) time. The analysis reveals that the maximum UTCI values were noticed over built-up areas compared to other land classes during daytime as well as nighttime. The results derived from the present study have shown the performance of WRF-UCM-derived UTCI reasonably portrayed the significant impact of urbanization on thermal comfort over the city and provided useful insights with regard to urban comfort and welfare.