Radioclimatic Variable Characterization for Tropical Microwave Link Applications

Abstract: One of the main factors impairing radio wave propagation is atmospheric refraction. To ensure a reliable radio link, accurate estimates of the refractivity gradient and geoclimatic factor are essential for determining the fade margin, a crucial component of radio-wave signal transmission. In this study, three years of data from 2019 to 2021, collected from six distinct locations in Nigeria, were utilized to analyze the radio-climatic variables in order to determine their influences on microwave linkages. The obtained values for surface refractivity show seasonal variation, with higher values during the wet season and lower values during the Harmattan. Makurdi, located in the north of the country, is mostly impacted by sub-refraction, whilst Lagos and Port-Harcourt, in the south, are impacted by super-refraction. The average refractivity gradient values for Makurdi and Yola are -35.2 and -30.62 N-units/km, respectively, with k factors of 1.30 and 1.32. In contrast, Lagos and Port Harcourt recorded values of -81 and -93. with k factors of 1.42 and 1.51. The findings also show that the shift of the intertropical discontinuity influences seasonal variations across the studied locations. Geoclimatic factor values vary seasonally and spatially. The results provide valuable insights for designing microwave wireless links in Nigeria. Keywords: Fade margin, Geoclimatic factor, Microwave links, Propagation, Surface refractivity.