An Illustrative Study of Surface Radio Refractivity in Awka, South Eastern Nigeria

This work investigates the radio refractivity over Awka, South Eastern Nigeria using meteorological
parameters of surface air temperature, pressure and relative humidity collected from 2013 – 2014
respectively, using Davis weather station vantage pro 2 (with Integrated Sensor Suite, ISS) positioned
close to the ground surface. The data were logged at 30 minutes interval continuously for each day
during the period. Hourly, daily and monthly averages of radio refractivity during dry and wet seasons
were calculated from the data obtained. The result indicated that the radio refractivity during the wet
season is greater than the dry season. This is as a result of variation in meteorological parameters
such as relative humidity and temperature which cause the radio refractivity to vary at different times
of the day; while the pressure variation seems to be insignificant. However, results of the refractivity
gradient shows, that the propagation conditions have varying degree of occurrence with superrefractivity
conditions observed to be prevalent throughout the two year period. The month of January
has the highest value of refractivity gradient while least of about -63 N- units per km occurred in July
and propagation implication bearing in mind that the lower the gradient (that is more negative) the
more super refractive is the troposphere, and the better the propagation conditions. The results
obtained from this work is useful to radio engineers for improving VHF/UHF terrestrial links based on
clear- air considerations. The analysis of this work has shown that the surface refractivity for the twoyear
period over Awka showed seasonal variations with high values in the rainy season and low
values in the dry season. The dry season was highly variable unlike the wet season refractivity which
had small variability. For radio wave propagation in Awka and environs the propagation condition
could mostly be super – refractive. But the month of January had the highest value of refractivity
gradient while the least occurred in July.