Effects of rain on microwave and satellite communications in equatorial and tropical regions

Abstract

Rain rates in Ilorin (8.30°N, 4.32°E), used as the main station, measured with an asynchronous rain gauge over a period of six years(1989-1992, 2000-2001), Ile-Ife (7.5°N, 4.5°E) and measurements of rain gauges and beacon measurements from equatorial stations, Brazil, Papua new Guinea(PNG), Indonesia, Kenya, Tanzania, Uganda and Cameroun have been utilized to characterize the effects of tropical and equatorial rains on microwave satellite communications. The tropical rains show the existence of a sharp change in the exceedances structure at rain rates of between 100mm/h and 110mm/h. The sharp changes are thought to be due to the effects of wind sorting, strong up draughts and instabilities associated with strong convective rains at these rain rates. The existence of the change in the exceedance structure at these rain rates indicates different rain rate models that may be applicable before and after the change. The measurements have also shown that for accuracy in the prediction of tropical rain attenuation the full cumulative distribution of the rain distributions will be more appropriate. The results have shown a lognormal approximation before the change and a simple exponential approximation after the change. The implication of this is a reduction in the power budget for rain attenuation computation in the tropics when the change in the intensity structure is taken into consideration.

Keywords: rain, exceedances, lognormal distribution, exponential distribution, attenuation

Nigerian Journal of Physics Vol. 17, 2005: 66-71