Difference of Urban Heat Island Effect among Representative Cities of Different Climatic Zones over Eastern China Monsoon Region

The spatial distribution and temporal variation of the Urban Heat Island Intensity (UHII) are analyzed by using the hourly surface air temperature (SAT) data from automatic weather stations during September 2012−August 2014 and January 2016−December 2017 over four cities, those are Changchun, Beijing, Wuhan, and Guangzhou. The annual mean UHII in built-up areas of these cities are found as 0.96°C, 1.06°C, 0.91°C, and 0.78°C, respectively. The UHII in northern cities is higher in spring and summer than in autumn and winter due to calm and inversion weather and higher anthropogenic heat release than in other seasons. However, the autumn UHII is the most obvious in southern cities beacause the clear sky and crisp air is conducive to the development of heat island, followed by the UHII of winter and summer, and the UHII difference among the four seasons is small. Besides, the diurnal variation of UHII in each city is characterized by a stronger UHII at night than during the day, with UHII beginning to decline (rise) in the early morning (afternoon). The amplitude of UHII diurnal variation is the largest in Wuhan due to several water bodies and the smallest in Guangzhou due to the mild climate. For the UHII diurnal variations, the steadily strong UHII period at night (day) is longer (shorter) in autumn and winter for the northern cities. The UHII difference between north and south climate zones has practical significance for urban planning and urban operations management.