Variation of urban vegetation cover and its impact on minimum and maximum heat islands

Abstract

Based on Landsat satellite imageries, the normalized difference vegetation index (NDVI) for the entire vegetation cover has been calculated at two times (i.e. winter and summer) of each year for 2008, 2013 and 2019. Concomitantly, we calculated the seasonal and annual minimum and maximum urban heat island (UHI) intensity, using daily minimum and maximum air temperatures measured at two different places: 1) at an urban site located on the roof of a building in the city center, 2) at a rural site at the countryside close to the city. The fractional areas with their ratios of vegetated spaces are also computed and the results show that the highest mean NDVI occurred in 2013 and the lowest in 2008 and 2019. The results showed that minimum UHI has positive values ranged from 3.4 to 6.4 °C while maximum UHI ranged from −0.7 to 0.3 °C and both have increased trends over the period. The linear relation between mean NDVI areas and minimum and maximum UHIs is found to tend weak, which demonstrate that vegetated areas correlate negatively with minimum UHI and positively with maximum UHI. Thus, urban vegetation should be maintained to reduce local intensity of UHI. Urban heat is a problem in cities, so this article described the changes in spatial patterns of vegetation cover and its linkage to minimum and maximum UHI in the Metropolitan city of Baghdad.