Assessment of Tropospheric Radio Refractivity and Its Variation with Climatic Variables Over Zaria, Nigeria

To achieve optimal performances, radio link/system planning and design must take radio refractivity estimation very seriously. This study  utilizes measured average daily temperature, relative humidity, and atmospheric pressure for forty-one-year period (1981–2021) obtained  from the National Aeronautics and Space Administration (NASA) archives for Zaria (latitude 11.100 N, longitude 7.680 E)  strategically located in Nigeria’s midland climate zone to calculate the monthly tropospheric radio refractivity and look into how it varies  with other meteorological factors and radio refractive index. The percentage of the contribution of dry term (Ndry) and wet term (Nwet)  to radio refractivity and refractivity gradient were investigated. The findings indicated that radio refractivity was higher during the rainy  season (August) and lower’during the dry season (February), with a maximum mean value of 350.8733 N-units and a minimum mean  value of 284.1975 N-units, respectively, found in those months. The wet term contributes to the significant fluctuation of the radio  refractivity, whereas the dry term makes up 76.03% of the total value. The gradient of mean refractivity estimated for Zaria was found to  be – 43.8709 N – units/km indicating super-refraction propagation condition.