Seasonal Variation of Radio Refractivity Index and Saturated Water Vapour Density Across Selected Sub-Sahara Stations

Water vapour is known to represent the amount of water in the atmosphere. However, periodic and regular variations in both radio refractive index (N) and saturated water vapour density (SWVD) were observed at selected Nigerian stations. This investigation used monthly air temperature, air pressure, and relative humidity data from four stations (Iwo, Ife, Ilesha, and Osogbo) collected from the soda (http://www.soda-pro.com) HelioClim website repository of MERRA-2 meteorological re-analysis data. However, for the research, there have been factors influencing radio signal transmission that operate in the troposphere, contributing to saturated water vapour. The result of the research showed that analysis of monthly MERRA-2 data indicated that N and SWVD peak in May (379 N, 20.50 g/m3) and trough in January (333 N, 14.00 g/m3). The results showed a strong seasonal dependence, with N and SWVD increasing by 13.5% and 46.4%, respectively, from dry to wet season. These findings have implications for optimizing radio system performance in Sub-Saharan Africa. Present study also revealed that radio refractive index and SWVD are generally higher in the wet season and lower in the dry season at the selected stations. As a result, the study concluded that in order to achieve good radio refractive index performance in Sub-Saharan Africa, the country must account for the variability of the meteorological parameters used in the study of radio refractive index and SWVD for the design of optimal system performance.