The ever-increasing demand on satellite communication systems has resulted in lower frequency bands becoming increasingly congested. The available radio wave frequencies above Ku-band are prone to signal attenuation due to rain. The rain data obtained from the Tropospheric Observatory Data Acquisition Network (TRODAN) of the Nigeria Space Research and Development Agency (NASRDA) located across the geographical zones of Nigeria were used to analyse the rain attenuation from 99.99% to 99.9% availability (i.e., 0.01% to 0.1% unavailability) of time. From the study, at 0.01% of time needed for radio communication system, rain rate values R 0.01 were found to vary from 125 mm/hr to 46.98 mm/hr. The R 0.01 values across the studied locations were subsequently used to estimate rain attenuation using the International Telecommunication Union-Radio (ITU-R) model. Attenuation results show corresponding increase as the path length of the terrestrial links increases. The attenuation due to the horizontally polarized waves is large compared to the attenuation of the vertically polarized waves at all frequencies and in all the locations of the study. It is also evident that availability requirement increases with attenuation.

Abstract. Data obtained from Nigerian Environmental Climatic Observing Program(NECOP) station located at the University of Lagos, Akoka were employed to study the variation of surface radio refractivity for Lagos. Attention were focused on seasonal variation because the diurnal variation though could be abrupt, but the period of occurrence is short compared to the seasonal variation of the surface