Equivalent 1-Minute Rain Rate Statistics and Seasonal Fade Esitmates in the Microwave Band for South-Western Nigeria

The knowledge of 1-minute integrated cumulative rain rate distribution is required for predicting the attenuation induced by rain on satellite and terrestrial microwave and millimetric links. In this paper, conversion coefficients are derived for estimating the equivalent 1minute rain rate statistics from those available in 5 and 30-minutes over Akure, South-Western Nigeria. The derivation is based on the power-law relationship existing between equiprobable rain rate statistics, while comparison is made with estimates available for other locations. Apparent in the result is the significant variation in the values estimated for similar observation periods over the years and across different locations. Form the evaluation of the coefficients derived for Akure, the 5-minute conversion provides a more satisfactory performance and hence more suitable for estimating the equivalent 1-minute rain rate statistics for Akure. Quantifying the seasonal precipitation variability, the point rain rates for wet (raining) and dry (harmattan) seasons are 80 and 20 mm/h respectively and the resultant impact on NIGCOMSAT 1-R link reveals that an additional fade margin of 4 and 1.7 dB would be required to meet a 99.99% system availability objective in the wet season, specifically at 12 and 10 GHz respectively.