Comparative Analysis of Rainfall Heights Over Geo-climatic Zones for Satellite Communication at Ku-Band in Nigeria

Abstract

Nigeria's diverse geo-climatic zones present varying challenges for satellite communications, particularly at Ku-band frequencies (12-18 GHz). Rainfall height is a critical parameter that directly influences signal propagation and the link margin, as such, must be taken into account when designing Ku-band satellite communication systems to ensure reliable and efficient communication. This study presents a comparative analysis of rainfall heights over Nigeria geo-climatic zones, the impact on Ku-band satellite communication system and a monthly zero degree isotherm height (km) across the selected locations. Data collected over three years from four locations, each representing a major geo-climatic zone of Nigeria, were analyzed using a purposeful sampling technique. The result shows seasonal variations of the Zero Degree Isotherm Height (ZDH) over Nigeria geo-climatic zones with lower heights occurring in January (4.1 to 4.15km) and December (4.18 to 4.2km) while peak heights occur during the middle months of the year (July-August), reaching approximately 4.42-4.43km. ESUT (Enugu) and FUTA (Akure) shows slightly higher values than PJAA (Abuja) and FUGUS (Gusau) most times of the year, particularly in August where it reaches about 4.43km. The distribution of measured ZDIH across the zones varies (4.109km – 4.431km) as against 4.5km predicted by the International Telecommunication Union-Radio (ITU-R). The measured rain height ranges from 4.46km to 4.79km across the zones as against 4.86km predicted by ITU-R for the same zones. ITU-R model maintains a constant height throughout the period, showing no seasonal variation. The study reveals that the ITU-R model overestimates the ZDIH by approximately 4.4-5.6% and the rain height by about 4.1-5.2% across Nigerian zones. Therefore, this substantial difference must be put into consideration as an important parameter in Meteorology and for estimating rain attenuation in satellite communication systems in Nigeria to avoid the overestimation of rain attenuation and subsequent over-engineering of satellite link budgets.