Assessment of Urban Heat Island and Urban Pollution Island Synergy During the Dry Season in Greater Accra, Ghana

Accra is the capital and most populated region in Ghana but the smallest in the land coverage area. People living within the region could be highly exposed to the worse impacts of poor environmental conditions. Urban heat island (UHI) and pollution island (UPI) are two predicaments of the urban environment that are exacerbated by rapid urbanization. It is crucial to understand the synergy between UHI and UPI. In this paper, the interaction between UHI and UPI was studied by analyzing the diurnal variation of air temperature and fine particulate matter (PM2.5) from purple-air sensors at six different sites in the capital. The observation revealed the existence of UHI and UPI with varying intensities. The UHI was nocturnal while UPI was more pronounced during daytime than night-time. The synergy analysis revealed some diurnal disparities which showed that UHI enhances UPI during the day while a coupling interaction at night-time resulted in strengthened nocturnal UHI in Accra. However, there were discrepancies in the interaction and the strength of the relationship at different sites. In summary, the synergy between UHI and UPI varies with location and may depend on the time of day, prevailing weather conditions, and other anthropogenic emissions. The findings also demonstrate the importance of addressing indiscriminate land use and necessitate the enforcement of existing urban planning laws within the country to mitigate the effect of air pollution amidst climate change and frequent extreme events which may exacerbate risk impact.