Abstract-The paper describes the modelling of the average rainfall rate distribution measured at different locations in South Africa. There are three major aspects this paper addresses: to develop a rainfall rate model based on the maximum likelihood method (ML); to develop contour maps based on rainfall rate at 0.01% percentage of exceedence; and re-classification of the ITU-R and Crane rain zones for the Southern Africa region. The work presented is based on fiveminute rainfall data converted to one-minute equivalent using a newly proposed hybrid method. The results are mapped and compared with conventional models such as the ITU-R model, Rice-Holmberg, Moupfouma and Crane models. The proposed rainfall rate models are compared and evaluated using root mean square and chi-square (χ 2 ) statistics. Then re-classification of the rain zone using ITU-R and Crane designations is suggested for easy integration with existing radio planning tools. The rainfall rate contour maps at 0.01% percentage of exceedence are then developed for South Africa and its surrounding islands.

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[1] Rain attenuation has a serious impact on the availability and performance of radio communication services operating in the frequencies above 10 GHz. In order to reliably predict rain attenuation for a given location, there is a need for studying monthly and seasonal rainfall variability, worst month and average worst month statistics of rain, and rainfall rate distribution models for the site under study. In this paper, the tasks are tackled by processing 5-year (a) rain rate data for selected sites in South Africa. The dependence of the percentage of the average year (AY) on percentage of time of the average worst month (AWM) of rainfall rate and the obtained rainfall rate distribution models for eight regions in South Africa are assessed by examining the root-mean-square (RMS), the average probability ratio (APR), and chi-square statistic (CHI) on the basis of measured data and the International Telecommunication Union recommendation (ITU-R) estimations.Citation: Owolawi, P. A., and T. J. Afullo (2007), Rainfall rate modeling and worst month statistics for millimetric line-ofsight radio links in South Africa, Radio Sci., 42, RS6004,

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