Diurnal and annual cycles of surface refractivity and related parameters in Minna, Central Nigeria

Abstract

Radio refractivity N exerts considerable influence on radio signals at VHF and higher frequency bands. In particular, surface refractivity correlates positively with radio field strengths, and knowledge of its temporal variability is important in predicting performance of terrestrial radio networks, especially at VHF and microwave frequencies. Knowledge of the variability of the atmospheric parameters from which N derives is also important for radio propagation and other applications such as Agriculture and Tourism. Measurement of atmospheric parameters is also necessary to update past records, especially in the light of climate change. Surface refractivity values derived from values of air pressure P, temperature T and relative humidity H measured for two consecutive years (2008-2009) in Minna (09037N, 06032E),Central Nigeria are statistically analysed to explore their diurnal and seasonal cycles, as well as their inter-relationships. The results reveal that surface refractivity and the related weather variables show clear diurnal and seasonal trends with discernible relationships. In particular, diurnal N values have high correlation with diurnal P values, while monthly averages of N and H are also highly correlated; and the hot weather generally experienced in the month of April in Minna may be attributed to a combination of high humidity and high temperature at surface level.