Quantifying Urban Morphology–UHI Relationships In Hot-Dry Climates: An Empirical Study From Nigeria

Abstract

Urban heat island (UHI) intensity in cities continues to intensify with rapid urbanization, yet empirical relationships between urban morphology and UHI formation in hot-dry climates remain poorly quantified. This study aimed to establish the relationship between urban morphological parameters and UHI intensity in Yola, Nigeria, a rapidly growing city in Sub-Saharan Africa’s hot-dry climate zone. Using 18 months of microclimate monitoring data from 12 strategically selected sites, measured UHI intensities ranging from 2.8°C to 4.2°C across different urban forms were recorded. Results showed a strong correlations emerged between UHI intensity and building density (r = 0.847, p < 0.001), vegetation cover (r = −0.776, p < 0.001), and impervious surface ratio (r = 0.812, p < 0.001). Building density exceeding 60–65% correlated with UHI intensification beyond 3.5°C, while vegetation coverage above 40% maintained UHI below 3.0°C. Diurnal analysis revealed a 195% UHI intensity increase from daytime (2.9°C) to evening peak (6.2°C at 18:00–21:00), with pronounced nocturnal persistence (4.8°C at midnight). Climate change projections (combined CMIP6/CORDEX-Africa climate model outputs (5-model ensemble) under RCP 2.6, 4.5, and 8.5) indicated potential UHI doubling to 8.5°C by 2050 under business-as-usual scenarios, though aggressive mitigation could limit intensification to 4.1°C. These findings provide empirical evidence for density controls, vegetation preservation requirements, and surface material regulations in rapidly urbanizing hot-dry regions globally.