Estimating the Variability of Tropospheric Radio Refractivity and Field Strength over Enugu, South-East Nigeria

Abstract

The field strength variability (FSV) assessment highlights the significant impact of atmospheric conditions on radio signal propagation. A diurnal variation in radio refractivity is the primary driver of FSV, with local topography and environmental factors also playing important roles. This study investigated the variation of tropospheric radio refractivity and field strength in Enugu, South-East Nigeria. Through a comprehensive measurement of temperature, humidity and pressure obtained from the network of Vantage Pro 2 automatic weather station installed at the study location for a period of six months (January 2024 to June 2024). Using the International Telecommunication Model (ITU-R model), radio refractivity was computed from the collected weather parameters, and subsequently the field strength. The results showed that, radio refractivity displayed diurnal variability with high values in the morning and late evening while low values were observed in the day time. Furthermore, the analysis of the results revealed that, during the months of January, February and March, more pronounced daily variations with lower minimum values between 292N to 332N were observed at about 13:00 hours local time and higher values between 300N to 350N in the morning (0:00 - 6:00) and evening (15:00 - 23:00).Moreover, the analysis of field strength variability showed that the months of January, February, and March (dry season) were marked by higher field strength values. In particular, January recorded the highest field strength value (7.4 dB). On the other hand, the months of April, May, and June (wet season) exhibited lower field strength values, with the lowest value (1.9 dB) observed in May. The results indicate a strong seasonal impact on field strength.