The Scattering of Radio Waves in the Lower and Middle Atmosphere

The evidence relating to the reflection of radio waves from levels below 80 kilometers is considered and apparatus used to investigate the reflection coefficients of these regions is described. The new experimental results here presented are not in agreement with those of earlier workers, but indicate that reflections from region B (below 10 kilometers) and region C (35 to 60 kilometers) are very weak and are due to scattering patches rather than reflecting strata. It is shown that reflections from region B are probably due to water molecules and that echoes with time delays corresponding to semipaths of 10-25 kilometers probably originate at scattering centers within the troposphere. The equivalent reflection coefficient of region C is discussed and the mechanism of formation of this region of ionization is briefly considered in connection with atmospheric temperature gradients.