Bistatic Microwave Probing of a Refractively Perturbed Clear Atmosphere

Abstract

Comprehensive calculations are carried out to predict the signal levels to be received by powerful 5- and 10-cm wavelength bistatic scatter systems from vertically thin but horizontally extensive layers of turbulently perturbed refractivity in the clear atmosphere. The results indicate that the model systems can detect regions having only modest refractivity perturbations throughout the entire depth of the troposphere. Although the horizontal coverage and the maximum signal levels decrease with increasing altitude of the scatter layer, the signals are sufficiently strong in the vicinity of the mid-path point to assure the reliable detection of extremely weak scattering layers. In particular, the tropopause should be detected routinely. Hazardous clear air turbulence should also be readily detected, at least in the vicinity of the mid-path. Vertical polarization is superior to horizontal polarization for large horizontal coverage. The shorter wavelength is also slightly superior to the longer, other things being equal. Comparison of the signals received by the bistatic system to the echo intensities received by a radar of equal characteristics shows the distinct advantage of the former. The results are also pertinent to trans-horizon scatter propagation.