Diurnal and seasonal trends and associated determinants of surface urban heat islands in large Bangladesh cities

Many surface urban heat island (SUHI) studies have been conducted around the globe, however there is still a lack of information available regarding the intensity of SUHI (SUHII) in Bangladesh cities. This study focused on diurnal and seasonal SUHI variability, temporal trends and possible drivers in five major cities. Mean annual daytime SUHII ranged from 2.88 degrees C for Dhaka to 0.84 degrees C for Rajshahi, while nighttime intensity varied from 1.91 degrees C (Chittagong) to 0.30 degrees C (Sylhet). The pre-monsoon period exhibited the greatest magnitude and the seasonal amplitude during the winter season was positive for Dhaka and Khulna but negative for the other cities. Correlation analysis indicated that a dense city population, a high degree of imperviousness and the absence of greenery were likely to act singly, or in combination, to increase urban warming within these cities. An increasing warming trend during daytime was observed. The urban population of Bangladesh is projected to increase substantially in future (i.e., to 81.4 million by 2029), so the findings of this study provide valuable insights into this warming issue and will assist in the development of effective local-scale climate change adaptation plans.