Refractivity gradient of the first 1km of the troposphere for some selected stations in six geo-political zones in Nigeria

Abstract

This paper presents the evaluation of refractivity gradient and the effective earth radius factor (k) analysed from the climatic profile values of air temperature, relative humidity and atmospheric pressure in the first 1Km of the troposphere over six (6) selected stations from the six geopolitical regions in Nigeria. The study utilized meteorological data from Satellite Sounding instrument by NASA USA. The meteorological parameters measured were extracted from MERRA MAIMCPASM V5.20 database software from January 2010 to December 2014 for each station. The result shows that the average values of the refractivity gradient and k-factor for the 5 years period of consideration are (40.2 N-units/km and 0.797 ≈ 1.0 N ) for Abuja, (40.3 N-units/km and 0.792 ≈ 1.0 N) for Enugu, (47 N-units/km and 0.773 ≈ 1.0 N) for Lagos, (43 N-units/km and 0.788 ≈ 1.0 N) for Port-Harcourt, (26.4 N -units/km and 0.862 ≈ 1.0) for Sokoto, (23.2 N -units/km and 0.876 ≈ 1.0) for Maiduguri respectively. The outcome of the k-factor was dependent on the type of season and the variability of k-factor showed that the value of 1.33 recommended by the ITU will either underrate or overrate k-factor value in each of the station under consideration. In conclusion, the local radio propagation condition in the troposphere for the selected six stations in Nigeria are predominantly sub-refractive based on the k-factor which is 43 > k > 0.