Assessing the urban heat island effect of different local climate zones in Guangzhou, China

The urban heat island (UHI) effect has significant implications on urban development, human health, and climate change. Local climate zones (LCZs) provide an objective and systematic classification of field sites for studying the UHI effect. Accurately characterizing the UHI features in each LCZ is fundamental to mitigating the UHI effect. This study aimed to analyze the UHI effect in six LCZs in Guangzhou. Temperature data were collected simultaneously using fixed-point measurements over 405 days from October 1, 2019 to March 31, 2022. The UHI characteristics of the LCZs under various weather conditions were analyzed by examining the hourly, daily, and seasonal UHI intensities (UHIIs). Consistent diurnal variation patterns were observed in the daily average UHII under different weather conditions but with varying peak values. Ideal days with weak winds and clear skies significantly contribute to the development of maximum UHII, occurring most frequently between 18:00 and 23:00 with a frequency of 45%. In comparison, UHI events on precipitation days have a lower frequency. Furthermore, UHI effects varied significantly among different LCZs, with higher UHII observed in high-density built-up LCZs compared to open low-rise LCZs. Variations were particularly pronounced during the night in autumn and winter with a maximum UHII mean of 5.30 °C. UHI event frequencies and hourly warming/cooling rates were also examined to provide a more comprehensive assessment of the UHI effects on LCZs. This study is of great significance for understanding the UHI characteristics within Guangzhou, and for guiding urban planning and management to mitigate UHI in LCZs.