No Universal Urban Form Heat Relationship: Contrasting Thermal Controls in African Cities

Liangyu Xian, Maoran Sun

Rapid urbanization and climate change have intensified urban heat island effects. Tropical African cities face particularly high heat vulnerability, yet they remain underrepresented in urban thermal research. Existing research often assumes universal morphology temperature relationships, lacking cross city comparative evidence and spatially rigorous nonlinear attribution in African contexts. This study examines daytime land surface temperature (LST) associations with 11 multi dimensional urban morphological indicators in Lagos and Nairobi, using a nested 2 km spatial block cross validation framework coupled with XGBoost and SHAP analysis. Results reveal markedly city specific regulation patterns. In compact, densely built Lagos, population density dominates, while vegetation morphology is the primary control in fragmented, greener Nairobi. Nonlinear threshold effects are detected for building density in Lagos and vegetation height in Nairobi, and single shot imagery systematically amplifies factor contributions compared with multi temporal composites. These findings demonstrate that urban morphology temperature relationships are not uniform across African cities, supporting context specific rather than unified heat mitigation planning.