## 3 Results and Discussion
### Effects of Rain Height on Rain-Induced Attenuation  
The estimated seasonal rain heights were applied to compute rain-induced attenuations at a typical Ku-Band downlink frequency of 12 GHz across the stations. The ITU-recommended rain heights were also used to compute attenuations at the same frequency to study the effects of rain height variability on satellite communication links. The attenuation plots of only six stations are presented in Figure 12a-f due to the similarity in the variability trends of some stations. There is a clear significant impact on the attenuations due to rain height variation in each season across the stations. Summer is generally characterized by very high rain heights, which results in the highest rain attenuation across all of the stations. At a 0.01% time exceedance, which translates to 99.9% signal availability per year, the maximum attenuation of about 11.59 dB was recorded in Durban, followed by Cape Town and Pretoria, while the minimum value of 9.06 dB was recorded in Upington, a semi-arid region with a drier climate. These attenuations were underestimated by the ITU recommendations, especially at Durban where the severity of rainy events was not fully captured. This could result in insufficient compensation in link budget calculations and consequently lead to signal outage. Both spring and autumn possess gradual switching trends as transitional seasons between two extreme weather seasons. Polokwane, Pretoria, and Nelspruit also experienced high attenuation during spring but slightly lower than in summer at percentages of exceedance less than 0.01%, which indicates a gradual switch to winter. The attenuations during the transition seasons are usually very close to each other but lie between the summer and winter values, as evident in Figure 12a-f. For instance, the autumn and spring attenuations \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Station**} & \multirow{2}{*}{**Season**} & **Measured** & **Estimated** & **Estimated** & **ITU Hr** & **ITU \%** \\  & & **Hr (m)** & **Hr (m)** & **\% diff** & **(m)** & **diff** \\ \hline \multirow{4}{*}{Bloemfontein} & Autumn & 4873.43 & 4946.63 & 1.50 & 4470 & 8.28 \\  & Winter & 4085.19 & 4113.66 & 0.70 & 4470 & \(-9.42\) \\  & Spring & 4326.5 & 4404.93 & 1.81 & 4470 & \(-3.32\) \\  & Summer & 4962.84 & 5013.21 & 1.01 & 4470 & \(9.93\) \\ \hline \multirow{4}{*}{Durban} & Autumn & 4813.44 & 4872.66 & 1.23 & 4085 & 15.13 \\  & Winter & 4070.6 & 4096.54 & 0.64 & 4085 & \(-0.35\) \\  & Spring & 4251.07 & 4359.18 & 2.54 & 4085 & 3.91 \\  & Summer & 4848.65 & 4924.1 & 1.56 & 4085 & 15.75 \\ \hline \multirow{4}{*}{Port Elizabeth} & Autumn & 4500.62 & 4564.46 & 1.42 & 3354 & 25.48 \\  & Winter & 3638.16 & 3727.71 & 2.46 & 3354 & 7.81 \\  & Spring & 3656.87 & 3791.51 & 3.68 & 3354 & 8.28 \\  & Summer & 4434.47 & 4550 & 2.61 & 3354 & 24.37 \\ \hline \multirow{4}{*}{Cape Town} & Autumn & 4216.26 & 4290.92 & 1.77 & 3123 & 25.93 \\  & Winter & 3326.86 & 3503.34 & 5.30 & 3123 & 6.13 \\ \cline{1-1}  & Spring & 3858.54 & 4017.6 & 4.12 & 3123 & 19.06 \\ \cline{1-1}  & Summer & 4673.15 & 4724.63 & 1.10 & 3123 & 33.17 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: _Cont._at 0.001% for Pretoria are 22.23 dB and 22.78 dB, respectively, whereas the ITU rain height recommended a constant value which is much lower. However, the autumn attenuation at Durban and Cape Town appears slightly higher than in spring due to the differential values in their corresponding rain heights. The smallest attenuation is experienced in winter across all of the stations, especially at Upington, which has as low as 17 dB at 0.0001%, whereas Cape Town shows around 24 dB, as shown in Figure 12d,f, respectively.