Temporal Variability and Meteorological Controls of Radio Refractivity over Lagos, Nigeria, 1995-2024

Abstract

This study investigates the temporal variability and meteorological controls of surface radio refractivity over Lagos, Nigeria, using monthly temperature, pressure, and vapour pressure observations from 1995–2024. Radio refractivity and its dry and wet components were calculated using the standard ITU-R formulation. Descriptive statistics, component variance decomposition, temperature-pressure cross-correlation, and linear, quadratic, and cubic regression analyses were used to characterise the refractivity series. The mean refractivity was 376.79 N-units, with the dry and wet components contributing 68.6% and 31.4%, respectively. Despite its smaller contribution to the mean, the wet component accounted for 109.42% of temporal variance, compared with 5.43% for the dry component, while covariance contributed −14.85%. Temperature and pressure showed a strong inverse zero-lag correlation . The linear trend was weak ; ), with negligible improvement from higher-order polynomial models. The work explicitly distinguishises between the components controlling mean refractivity and those controlling its temporal variability, demonstrating that atmospheric moisture is the dominant driver of refractivity fluctuations over Lagos despite the dominance of the dry component in the mean state.