The Influence of Disdrometer Channels on Specific Attenuation due to Rain Over Microwave Links in Southern Africa

The influence of raindrop channels on the measured rain rate and specific rainfall attenuation in Durban (29°52'S, 30° 58'E), South Africa for six rain rate values: 1.71, 4.46, 22.97, 64.66, 77.70 and 84.76 mm/hr selected from the rain events that occurred on the 27th December 2008 is analyzed in this work. Consecutive and alternate drop channels are removed to study the influence of raindrop diameters on the overall measured rain rate. The three-parameter gamma and lognormal models are used for the purpose of analysis. In general and for the two models considered, the lower channels (channels 1 to 5) do not alter significantly the overall rain rate and equally produce minimal attenuation. The critical raindrop channels contributing the larger percentage to the overall rain rate are created by D ≥ 0.771mm. The deviations of the measured and estimated rain rates are very small for all the rainfall rates selected. The estimation of the specific rain attenuation at frequency of 19.5 GHz is also discussed. The error estimation using the two models are also analysed.