Spatiotemporal Analysis of Surface Energy Balance Dynamics Over Degraded Drylands in Borno State

Land degradation in Nigeria's North East zone has altered the surface energy balance across extensive dryland areas of Borno State, modifying sensible and latent heat partitioning with feedbacks on local temperature, moisture availability, and mesoscale circulation. This study analytically examines spatiotemporal dynamics of the surface energy balance over degraded drylands in Borno State using MODIS land surface products combined with ERA5 atmospheric reanalysis data for the period 2015 to 2023. The net radiation, sensible heat flux, latent heat flux, and Bowen ratio were derived from the Surface Energy Balance Algorithm for Land (SEBAL) applied to cloud-free MODIS Terra scenes during dry and wet season periods. Multi-temporal LULC classification was used to stratify the study area into degraded bare soil, sparse shrubland, and recovering vegetation classes. Results reveal that degraded bare soil areas exhibit mean dry-season Bowen ratios of 8.2, indicating extreme dominance of sensible over latent heat flux, compared to values of 2.1 over recovering shrubland areas. The associated increase in sensible heat flux over degraded zones drives enhanced afternoon boundary layer instability, evidenced by significantly higher convective available potential energy values that paradoxically increase convective storm initiation potential even as surface moisture is depleted. Long-term trends show that degradation has expanded the high Bowen ratio zone northward by approximately 45 kilometres since 2015. Implications for regional climate feedback mechanisms and land restoration planning in Borno State are discussed. Keywords: surface energy balance, SEBAL, dryland degradation, Borno, Bowen ratio.