Diurnal and Seasonal Variation of Surface Refractivity in Minna and Lapai, North Central Nigeria

Spatial and temporal variations of surface refractivity, Ns, in the troposphere are important parameters in designing terrestrial communication links. This research work examines the effect of variations of meteorological parameters on surface radio refractivity during dry and wet seasons in Minna and Lapai (2011-2013). The data on surface temperature, humidity and pressure collected from the Tropospheric Data Acquisition Network (TRODAN) weather stations installed at the Federal University of Technology, Minna, and at Ibrahim Badamasi Babangida University, Lapai, were used for the computation of radio refractivity. The hourly and monthly averages of radio refractivity during dry and wet seasons were calculated. The results showed that surface refractivity varied diurnally and seasonally in both stations. Refractivity values were high during the early morning and night hours and decreased rapidly during the afternoon hours. Values of refractivity were also generally low during the dry season months and high during the wet season months. It was also observed that refractivity values were higher at Lapai than Minna in dry season months. The result also shows that diurnal refractivity variation is attributed to atmospheric phenomena while seasonal variation is caused by the climatic conditions of the regions. Maximum values of 350 N-units in August in 2011, 343 N-units in July in 2012 and 347 N-units in August in 2013, while the minimum values of 275 N-units in January in 2011, 278 N-units in March in 2012 and 273 N-units were recorded in February for Minna. Surface refractivity has maximum values of 350 N-Units in August (2011), 347 N-Units in August (2012) and 349 N-Units in September (2013), while minimum values of 289 N-Units, 290 N-Units and 297 N-Units occurred in January in 2011, 2012 and 2013 respectively for Lapai.