Seasonal Variations of Urban Heat Island Intensity in a Tropical City Using Local Climate Zone Mapping: A Case Study of Singapore

Urbanization and land cover transformations significantly influence city microclimates, leading to phenomena such as the urban heat island (UHI) effect, where urban areas experience higher temperatures than their rural counterparts. This effect is particularly pronounced in tropical cities like Singapore, which are highly susceptible to climate change impacts.

This study investigates UHI's intensity and temporal dynamics at both surface (UHI_surface) and canopy (UHI_ucl) levels during Singapore's Northeast Monsoon and First Inter-Monsoon seasons. Employing a multi-method approach, we integrated Local Climate Zone (LCZ) classification, meteorological data, and remote sensing techniques. A detailed LCZ map of Singapore was developed using Geographic Information System (GIS) tools, and thermal satellite imagery was analyzed to assess spatial patterns of the UHI_surface. Additionally, data from fixed meteorological stations were utilized to quantify UHI_ucl intensity.

Our findings indicate that UHI intensity at both levels is higher during the First Inter-Monsoon compared to the Northeast Monsoon. Compact LCZs (1–3) and industrial zones (LCZs 8 and 10) consistently recorded the highest temperatures for both UHI_surface and UHI_ucl across seasons. Thermal satellite imagery revealed that during the First Inter-Monsoon, compact LCZs (1–3) were up to 3°C warmer than open LCZs (4–6) during the day and 2°C warmer at night. Moreover, green areas (LCZ A) were found to be approximately 8°C cooler than built-up LCZs during the day and 2–4°C cooler at night.

These findings confirm that tropical cities are consistently hotter than their rural surroundings and exhibit higher UHI intensity, particularly in compact and industrial zones. The study underscores the significant role of climatologists in equipping urban planners, architects, and policymakers with essential data and insights. Such collaboration is crucial for designing sustainable urban environments and implementing effective strategies to mitigate urban overheating in tropical climates, thereby enhancing resilience to climate change.