SPATIAL ANALYSIS OF NET RADIATION AND SENSIBLE HEAT FLUX ACROSS SELECTED SOUTH-SOUTH STATES IN NIGERIA

*Nworah, O.A.; Weli, V.E.; and Nwagbara, M.O.

Department of Geography and Environmental Management, University of Port Harcourt, Port Harcourt, Rivers state

*Corresponding Email Address: otasnworah@gmail.com

Abstract

The increase in population invariably translates to higher demand for energy, exacerbating atmospheric pressure. Continuous environmental exploitation activities influencing urbanization and deforestation have overtime impacted on the surface energy flux. The study carried out spatial analysis of net radiation and sensible heat flux of Akwa Ibom, Cross River and Rivers states in Nigeria. The remote sensing data sources were from Surface Energy Balance Algorithm for Land (SEBAL) Algorithm with Landsat 8, OLI & TIRS sensors data downloaded from USGS site (2021). The downloaded imageries were imported into the ArcGIS 10.7 environment where further geospatial analyses were performed. The computation for net radiation was from surface albedo (𝛼), with land surface temperature K and solar constant of 1367 W/m² and earth sun distance of 0.9845086. For sensible heat flux, these parameters were utilized: Soil-adjusted vegetation index (SAVI), Leaf area index (LAI), momentum roughness, wind speed, temperature gradient and aerodynamic resistance. Findings revealed minimum net radiation values of 411.462 W/m² for Akwa Ibom state; 416.415 W/m² for Cross River state; and 403.537 W/m² for Rivers state. The highest maximum net radiation of 1231.15 W/m² was observed in Cross River state. The range of sensible across states were between 476.95 (H) and 47.64 (H) for Akwa Ibom state; and between 614.34 (H) and 178.67 (H) for Cross River state; and between 596.49 (H) and 136.26 (H) for Rivers state. Findings showed that anthropogenic activities have a significant effect on surface energy balance. Thus, higher surface heat fluxes experienced in built up areas can be mitigated through afforestation and urban greening especially in cities across south-south states Nigeria.     

Keywords: Net radiation, Sensible heat flux, Spatial analysis, Landsat OLI, SEBAL Algorithm, ArcGIS 10.7