Radio refractive index and refractive index gradients variation in a tropical environment

Abstract

This paper investigates variation of radio refractivity with related weather parameters and refractivity gradient with altitude. Three years (2013-2015) upper air atmospheric data of temperature, pressure and relative humidity for Abuja were obtained from the Nigerian Meteorological Agency (NIMET). The result shows that temperature, pressure and relative humidity decreases with increasing altitude. Radio refractivity values over Abuja are observed to be decreasing with increasing altitude and values in the rainy season are higher than dry season with a maximum of 344.1 N-units recorded in August and a minimum 277.5 N-units recorded in January. The average refractivity gradient for both dry and wet months is -30.6 N-units/km and the average k-factor as 1.25 which is in agreement with the condition of Sub-refraction.