Variability of the propagation coefficients due to rain for microwave links in southern Africa

Abstract

[1] We use the Mie scattering approach and the dielectric model of Liebe to determine the propagation coefficients and rain attenuation distribution for four locations in Botswana, southern Africa, using R 0.01 = 68.9 mm/h for Gaborone, R 0.01 = 137.06 mm/h for Selebi-Phikwe, R 0.01 = 86.87 mm/h for Francistown, and R 0.01 = 64.4 mm/h for Kasane over the frequency range of 1-1000 GHz. The results show that the extinction coefficients depend more strongly on temperature at lower frequencies than at higher frequencies for lognormal distribution. The absorption coefficient is significant but decreases exponentially with rain temperature at lower microwave frequencies. The application of the proposed model with various distributions is corroborated using practical results for Durban in South Africa.Citation: Mulangu, C. T., and T. J. Afullo (2009), Variability of the propagation coefficients due to rain for microwave links in southern Africa, Radio Sci., 44, RS3006,

Seasonal Analysis and Prediction of Rainfall Effects in Eastern South Africa at Microwave Frequencies

“…The nth truncation of the infinite series in (12) can be determined from the works of Bohren and Huffman [37] and of Mulangu and Afullo [4]. The solution for nth truncated values of a n (m, α) and b n (m, α) of the forward scattering amplitude, s(0), can be found using a combination of special spherical Bessel functions for spherical raindrops [38,39].…”

“…Authors have attributed the significance of rainfall attenuation to the spatial non-homogeneity of rainfall droplets, which usually result in absorption and scattering of propagated signals [3][4][5]. Although, worldwide approaches have been recommended by ITU-R in their rainfall design templates available in [6][7][8], there persists a problem of exactness and suitability since rainfall is dependent on climatic variation around the world.…”

Computation of rain attenuation using forward scattering in the south african coast

“…The details on the link setup at the receiver and the transmitter end are explained [4,5,6]. Mulangu et al came up with analytical model of drop size distribution based on existing models such as Laws and Parsons (LP) [7] Marshall-Palmer (MP), Weibull (WB) [8], Joss Dizzle (JD), Joss Thunderstorm (JT) [8] and lognormal (Thunderstorm Showers (TS), Tropical Thunderstorm (TT), Continental Thunderstorm (CT) and Continental Showers (CS)) [9], and from measurements made in [4].…”

Determination of rain attenuation from electromagnetic scattering by spherical raindrops: Theory and experiment

“…The approach of this work is similar to the work performed by Moupfouma [1997], but differs in two ways. First, while Moupfouma obtains his scattering amplitudes from oblate spheroidal raindrop calculated by Uzunoglu et al [1977] and Morrison and Cross [1974] who used the Ray complex refractive index in their simulations, in this presentation, the scattering amplitudes are calculated from spherical raindrop using the Liebe model [ Liebe et al , 1991] to compute the refractive index of the rain (water) drop, a method also employed by Mätzler [2002b] and more recently by Mulangu and Afullo [2009]. Second, while Moupfouma develops his rain attenuation coefficients from the imaginary part of the scattering amplitudes from the oblate spheroidal raindrop, in this paper we determine the rain attenuation coefficients from the real part of the extinction cross sections of the spherical raindrops, which is calculated from the real part of the spherical scattering amplitudes.…”