Comparative analysis of land–atmosphere interactions across three contrasting ecosystems in the West Sudanian Savanna

Study region: The Sudanian Savanna in northern Ghana and southern Burkina Faso is undergoing extensive land use change due to rapid population growth, altering surface–atmosphere interactions and regional climate dynamics.

Study focus: Limited data availability hampers observation-based assessments of land use change (LUC) impacts. To address this, we conducted a multi-year analysis of energy fluxes and land–atmosphere coupling using eddy covariance (EC) data from three contrasting ecosystems: near-natural savanna, cropland, and degraded grassland. We examined energy balance partitioning and derived surface parameters such as surface conductance. Despite similar climate and soil conditions, the near-natural savanna exhibited 30% higher net radiation and nearly half the albedo (0.16) of the degraded grassland (0.29). Evaporative fraction (EF) at agricultural sites was up to 30% lower during the dry season and monsoon transitions. Partial correlation analysis identified leaf area index (LAI) and upper soil moisture as key drivers of these differences, with EF most sensitive to LAI at the degraded grassland (r = 0.54) and least sensitive to soil moisture at the savanna site (r = 0.23). ... mehrThese results underline the complexity of LAI dynamics across ecosystems, particularly given uncertainties in tree phenology and variable tree cover.

New hydrometeorological insights for the region: Land–atmosphere coupling remained consistent across the three ecosystems during most WAM seasons but differed markedly during the drying phase. The results highlight the role of land cover in shaping surface fluxes and underscore the importance of long-term flux observations to understand LUC impacts on regional climate and hydrology.