Parametrization of drop size distribution with rain rate for microwave and millimeter wave applications in Central Africa

The estimation and prediction of the rain attenuation in a location are depending on a careful choice of the raindrop size distribution model. Since the rain rate is easier to observe than the raindrop size distribution (DSD), it is convenient to express the DSD in terms of the rain rate only. To this end, the data utilized in this work are collected using a Parsivel2 disdrometer located in Douala (4° 03′ N, 9° 42′ E), Cameroon. The lognormal distribution is adjusted to the measured data to model the DSD. The method of moments is adopted for the evaluation of the raindrop size distribution parameters. Parameters are expressed as functions of R only. The Mie diffusion approximation at a temperature of 25 °C for spherical drops is used to derive the diffusion function. The parameters showed a good fit to the observed DSDs for rain rates below 20 mm/h. A comparative study of the proposed model is made with models from West Africa with a good correlation of the order of 97% between the parameters of the lognormal distribution NT, Dg, and R. The proposed model is used to estimate the specific rain attenuation at 5–150 GHz. The specific rain attenuation increases between 10 ≤ f≤ 80 GHz, with a corresponding increase in the frequency. Above 80 GHz, there is some consistency of the specific rain attenuation, despite the increase in frequency and a stability from 130 GHz. The estimated attenuation will be useful for the design and allocation of adequate fading margins to achieve the expected quality of service in a radio communication system operating in this region.