helyne/ouaga-urban-heat-drivers

Cross-city, satellite image-based insights into predictors of urban heat hot-spots in Ouagadougou, Burkina Faso and Da Nang, Vietnam during 2024 # Low Built-Up Density Emerges as a Key Driver of Heat Extremes over the Sahel > Analysis codebase for the Impact Scholars Program 2025–2026 micropublication of the same name. The rendered paper and Zenodo DOI links are in the Citation section below. ## Citation > Lindner, E., Adamson, H., Ajadi, S. A., Christa, S., & Hagan, D. F. T. (2026). *Low Built-Up Density Emerges as a Key Driver of Heat Extremes over the Sahel*. Impact Scholars Program Micropublication. DOI: * * A `CITATION.cff` will be added once the Zenodo DOI is minted. ## Project Summary This project investigates what drives **intra-urban surface heat hotspots** in Ouagadougou, the capital of Burkina Faso — a fast-growing Sahelian city facing extreme heat during its March–May hot season. We combine satellite-derived land surface temperature (Landsat 8/9), spectral indices (Sentinel-2), and ancillary geospatial layers (DEM, distance to water and roads, built-up and green density from ESA WorldCover) to predict where hotspots emerge and to test which features causally drive them. Three machine-learning classifiers (XGBoost, Random Forest, SVM) are trained on the same predictor stack; the best-generalising model (XGBoost, F1 = 0.70, κ = 0.67) is then explained with SHAP for predictor importance, and the SHAP-highlighted predictors are passed to Geographical Convergent Cross-Mapping (GCCM) to test causal directionality against LST. **Headline finding.** In semi-arid Sahelian Ouagadougou, *lower* built-up density is associated with hotter surfaces — the opposite of what is observed in humid tropical cities. The mechanism is that low built-up density exposes bare soil with high solar absorptivity and negligible evapotranspiration, rather than displacing the cool vegetated land that drives the classical urban heat island. The reversal points to compact urban form and water-body preservation as climate-appropriate mitigation strategies for Sahelian urban planners. ## Meet the Team! | Author | Affiliat …