Surface urban heat island intensity in five major cities of Bangladesh: Patterns, drivers and trends

There is currently a lack of knowledge regarding the spatiotemporal variation of day and night surface urban heat island intensity (SUHII) in the major cities of Bangladesh. These cities have a large population base and generally lack the resources to deal with rapid urbanisation impacts, so any increase in urban temperature has the potential to affect people both directly (due to heatwave conditions) or indirectly (due to loss of livelihood). Time series diurnal (day/night) MODIS land surface temperature (LST) data for the period 2000-2019 was used to produce baseline information about SUHI intensity, drivers and temporal trends. Five large cities were selected based on population size and historical urban expansion rates. Results indicated that annual SUHII was greater in the larger cities of Dhaka and Chittagong than in the smaller cities. SUHII observed during the day was also greater than at night. Population (in terms of city size and surface cover), lack of greenness and anthropogenic forcing were major factors affecting SUHII. Trend assessments revealed positive trends during daytime in four out of five cities, while one city recorded negative trends at night. The findings may provide new insights into impacts arising from rapid urbanisation and demographic shifts.