Analysis of Radio-Radar Propagation Conditions Using Satellite-Viewed Cloud Cover and Rawinsonde Observations

The purpose of this study was to investigate how well the type and variability of satellite-viewed cloud cover may be used to describe the occurrence and variability of anomalous propagation conditions over areas of various sizes. In the investigation six cases were chosen for study covering periods when high received signal levels on the Berlin-Bocksberg-Breistsol tropospheric-scatter communication links indicated the probable occurrence of anomalous propagation. Rawinsonde data over an extended area surrounding the tropospheric scatter links were processed to compute refractivity gradients between the surface and the 700-mb level. These refractivity gradients were plotted on DMSP satellite photographs that showed the cloud cover (or its absence) over the network of rawinsonde stations. Comparison of the cloud photographs and superimposed refractivity graidents showed considerable variation in height and magnitude of large negative refractivity graidents at adjacent stations even though the stations appeared to have similar cloud cover, or clear skies. The major reason for the variability in refractivity graidents at adjacent stations is considered to be the inadequacy of the rawinsonde data. In particular, the small number of data points in the rawinsondes taken at some of the stations did not describe the atmospheric structure in sufficient detail to define superrefractive or trapping gradinets that may have existed over the stations.