Spatial Analysis of Surface Urban Heat Islands in Four Rapidly Growing African Cities

• Published in: Remote sensing (Basel, Switzerland) Vol. 11; no. 14; p. 1645
• Main Authors: Simwanda, Matamyo, Ranagalage, Manjula, Estoque, Ronald C., Murayama, Yuji
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 10.07.2019
• Subjects: African cities; Central business districts; Cities; Climate; Density; Environmental conditions; Environmental impact; Environmental science; Green infrastructure; green space; Heat; impervious surface; Land surface temperature; Land use; Landsat; Landsat data; Landsat satellites; Landscape; Landscape architecture; Open spaces; Remote sensing; Rural areas; Seasons; Spatial analysis; Statistical analysis; Studies; Temperature; Urban areas; Urban environments; urban heat island; Urban heat islands; Urban planning; Urbanization; Vegetation; Netherlands; Sri Lanka; Japan; Africa; Zambia; Nigeria; Kenya; Ethiopia; Addis Ababa Ethiopia
• ISSN: 2072-4292; 2072-4292
• DOI: 10.3390/rs11141645

Africa’s unprecedented, uncontrolled and unplanned urbanization has put many African cities under constant ecological and environmental threat. One of the critical ecological impacts of urbanization likely to adversely affect Africa’s urban dwellers is the urban heat island (UHI) effect. However, UHI studies in African cities remain uncommon. Therefore, this study attempts to examine the relationship between land surface temperature (LST) and the spatial patterns, composition and configuration of impervious surfaces/green spaces in four African cities, Lagos (Nigeria), Nairobi (Kenya), Addis Ababa (Ethiopia) and Lusaka (Zambia). Landsat OLI/TIRS data and various geospatial approaches, including urban–rural gradient, urban heat island intensity, statistics and urban landscape metrics-based techniques, were used to facilitate the analysis. The results show significantly strong correlation between mean LST and the density of impervious surface (positive) and green space (negative) along the urban–rural gradients of the four African cities. The study also found high urban heat island intensities in the urban zones close (0 to 10 km) to the city center for all cities. Generally, cities with a higher percentage of the impervious surface were warmer by 3–4 °C and vice visa. This highlights the crucial mitigating effect of green spaces. We also found significant correlations between the mean LST and urban landscape metrics (patch density, size, shape, complexity and aggregation) of impervious surfaces (positive) and green spaces (negative). The study revealed that, although most African cities have relatively larger green space to impervious surface ratio with most green spaces located beyond the urban footprint, the UHI effect is still evident. We recommend that urban planners and policy makers should consider mitigating the UHI effect by restoring the urban ecosystems in the remaining open spaces in the urban area and further incorporate strategic combinations of impervious surfaces and green spaces in future urban and landscape planning.