Long-Term Characterization of Vertical Radio Refractivity Gradients and Tropospheric Propagation Conditions over North-Central Nigeria Using ERA5 Reanalysis Data

Usman S Lami, Ikechiamaka N Florence, Akinbolati Akinsanmi, Isaac H Daniel, Owolai J Adeyemi, Abubakar Dalhat, Stephen C Nnochin, Akusu O Christiana, Mansur Bala, Bolorunduro C Blessing, Mohammed Mohammed, and Adamu Idris
2026-02-19 6 views 2 downloads

 

This study presents a comprehensive long-term evaluation of vertical radio refractivity and refractivity gradients over selected locations in North-Central Nigeria. Forty-one years (1980– 2020) of meteorological data obtained from the ERA5 reanalysis dataset of the European Centre for Medium-Range Weather Forecasts (ECMWF) were analyzed. Air temperature, atmospheric pressure, and relative humidity at heights of 12 m, 100 m, and 250 m above ground level (AGL) were used to compute radio refractivity using ITU-R formulations. Vertical refractivity gradients were subsequently derived and interpreted within established propagation regime classifications. Results reveal a consistent decrease in refractivity with increasing altitude across all locations. Wet-season refractivity values exceed dry-season values due to enhanced moisture contribution to the wet refractivity component. Mean vertical refractivity gradients were -125.65 N/km in Minna, -87.36 N/km in Lokoja, and -77.54 N/km in Jos. These values exceed the standard atmospheric gradient (? -39 N/km) in magnitude, indicating persistent super-refraction conditions, particularly in lowland and humid environments. The findings demonstrate that regional topography and atmospheric moisture distribution significantly influence radio wave bending characteristics. Incorporating location-specific vertical refractivity gradients into terrestrial propagation models is essential for improving reliability and interference prediction in subtropical continental climates.

 

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