Statistics of differential rain attenuation on adjacent earth-space propagation paths

The centimeter wavelength attenuations occurring simultaneously over a multitude of earth-space propagation paths were simulated by forty hours of observations of the three-dimensional radar reflectivity structure of rain in the Montreal area. The differences between the attenuations occurring simultaneously over pairs of paths to a common point at the ground were compiled as a function of angular path separation, viewing direction, radio frequency, and system margin. Values of angular separation from 2 to 9 degrees, radio frequencies from 11 to 30 GHz, elevation angles from 5 to 30 degrees, and system margins from 2 to 10 dB were considered. Results show that the cumulative distributions of differential attenuation is effectively characterized by the attenuation difference occurring during 1 percent of the time that the carrier signal suffered some attenuation, but not an attenuation exceeding the system margin. In addition, it was found that a simple analytical function of the system parameters can be used to express this characteristic differential attenuation.