Abstract
Rapid urbanization is one of the most crucial issues in the world of the 21st century. Notably, the urban heat island phenomenon is becoming more prominent in megacities and their hinterlands in temperate and subtropical climatic regions. In the daytime in summer, there exists a high possibility of accelerating the land surface temperature (LST) in desert cities, due to the alterations made by human beings in the natural environment. In this study, we investigate the spatial formation of LST in a tropical sub-Saharan city of Accra, a gateway to West Africa, using Landsat data in 2003 and 2017. Machine learning techniques and the different spatial and statistical methods such as tasseled cap transformation (TCT), urban-rural gradient, and multiresolution grid-based and landscape metrics were employed to examine procured land use/cover (LUC) and LST maps. LUC was classified into five categories: Built up, Green 1, Green 2, Bare land, and Water. The results of the analysis indicate that Built up, Green 2, and Bare land had caused the highest heating effect while Green 1 and Water had caused the considerable cooling effect during the daytime in Accra. The urban-rural difference in LST recorded 1.4 °C in 2003 and 0.28 °C in 2017. The mean size, mean shape, largest patch, and aggregation of Built up, Green 1, and Green 2 had a strong relationship with the mean LST. It is essential for urban planners to carefully examine the formation and effect of the urban heat island (UHI) for sustainable urban development and landscape policy toward mitigation and adaptation planning in Accra.
Highlights
Urbanization is one of the most fundamental worldwide phenomena in this century
We identified that the land surface temperature (LST) value of Accra in 2003 and 2017 was dependent on land cover categories (LCCs), and on different environmental factors such as significant air masses, dust, humidity, solar radiation, and air moisture when the Landsat thermal band imageries were investigated
Our study indicates that the mean LST is statistically significant with the density of the Built up, Green 1, and Green 2 in both urban-rural gradient analysis and multiresolution grid-based analysis in 2003 and 2017 (Figures 6 and 7)
Summary
Urbanization is one of the most fundamental worldwide phenomena in this century. Rapid urbanization has caused socio-economic advancement, including urban infrastructure development, improvement of the transport system, health care, etc. [1,2]. Rapid urbanization has caused socio-economic advancement, including urban infrastructure development, improvement of the transport system, health care, etc. Urbanization in developing countries has brought various socio-ecological problems, such as deforestation [3,4], overuse of energy [5,6], environmental degradation [7,8], air pollution [9], unhealth, and urban heat island (UHI) [10,11]. The UHI phenomenon results from the relative rise of land surface temperature in the urban areas compared to the surrounding rural environs [11,12,13]. Canopy layer UHI and boundary layer UHI are measured to calculate atmospheric UHI, while land surface temperature (LST) is used to determine surface
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