Analysis of Urban Heat Island Effect, Heat Stress and Public Health in Colombo, Sri Lanka and Shenzhen, China

Human health, energy and comfort are determined by the climate that remains in the physical environment. Regarding urban climate, few studies assess the urban heat island effect, heat stress, and public health as geographical representations. This study seeks to fill this gap by selecting Colombo, Sri Lanka, and Shenzhen, China, comparatively, two coastal cities with different climate conditions. We quantified and compared the effects of heat waves and their impacts on public health and the effect of urbanization on urban heat islands (UHI). Heat-related public health issues have been calculated using the Wet-Bulb Globe Temperature (WBGT) index. The Urban Heat Island (UHI) effect was analyzed using Land Surface Temperature (LST), created based on Landsat images obtained in 1997, 2009 and 2019. A rapid increase in temperature and humidity creates an uncomfortable environment in both cities, but apparent differences can be observed in climatic phenomena. During the summer (June to August), the prevailing atmospheric condition in Shenzhen makes a "Very severe stress" with Heatstroke highly likely. Nevertheless, seven months (November to April) are found as "Comfortable" without having any heat-related health injuries. However, Colombo has never been classified as "Comfortable" throughout the year. Out of twelve, five months (April to August) are found as "Very severe stress" with Heatstroke highly likely. When considering the urban expansion and UHI, a fast expansion can be observed in Colombo than in Shenzhen. Consequently, with the more severe heat-related public health and rapid urban heat island expansion, Colombo makes it more stressful than Shenzhen city. Our findings highlight the comparison between heat-related public health and urban heat island between two coastal cities with different climate conditions and under rapid urbanization processes. Therefore, it is imperative to assess these risks and respond effectively.