Impact of future urbanization on temperature and thermal comfort index in a developing tropical city: Ho Chi Minh City

This study examines the climate impact of future urbanization on the urban heat island effect over one of the developing megacities in tropical Southeast Asia, the greater Ho Chi Minh City area, using a dynamical downscaling approach with a high-resolution regional climate model coupled to urban canopy model. Simulations incorporate different land use/cover and anthropogenic heat release data sets for the current and future periods, while the boundary condition was fixed in the current time to detect only the impact of urbanization. Furthermore, human thermal comfort due to changes in the thermal environment was examined by analyzing the temperature-humidity index. Simulated results show that the increase in the surface air temperature is approximately 0.22 °C in the preexisting urbanized area and approximately 0.41 °C in new highly urbanized areas. The main factor in these changes is conversion from agricultural or grassland to urban structures, which results in increased sensible heating and decreased latent heating. Simulated results also show that despite the increase in air temperature, there is no significant change in thermal comfort. This is because human comfort is not only determined by temperature alone, but also by relative humidity. Urbanization increases temperatures, but decreases evaporation, which then decreases the relative humidity.