Assessment of Tropospheric Variation of Radio Refractivity and Field Strength Variability over Some Selected Stations in Northern Nigeria

The effects of meteorological parameters on the tropospheric radio refractivity and field strength variability cannot be overemphasised especially at the lower troposphere. The variability of tropospheric radio refractivity and field strength over selected fourteen stations in northern Nigeria has been assessed from daily meteorological data of pressure, temperature and relative humidity for the period of 12years (2003-2014). The data were sourced from the archive of European Re-Analyzed data (ERA Interim). The variables were computed using theoretical formulations and regression analysis was carried out to obtain the degree of influence of the meteorological parameters on surface refractivity. The result revealed a seasonal variation with maximum refractivity of about 424 N-unit in the wet months and minimum refractivity of about 248 N-unit in the dry months. Also, the stations in the guinea savannah showed a higher refractivity than the stations in Sudan and the Sahel region. This could be partly attributed to the reduction in humidity enhanced by a distance between the Inter Tropical Discontinuity (ITD) and the stations. Moreso, a higher field strength of about 28 dB during dry months and a lower field strength of about 2 dB during the wet months were observed. The study has revealed a strong correlation between the relative humidity and refractivity in all the three geo-climatic zones of northern Nigeria.