RADAR ECHOES FROM A CLOUDLESS COLD FRONT

Abstract

A recent radar observation of a line of echoes associated with a fast-moving cold front is described. The novel feature of the observation was the complete absence of any precipitation and cloud formations to which the echoes would otherwise be attributed. Various conceivable explanations for the possible cause of the echoes are examined and it is concluded that the most plausible cause resides in microwave scattering by index of refraction gradients. A frontal model is deduced which, if correct, serves to explain efficient mixing of air of different refractive index. The meteorological significance of the observation is examined and suggestions offered for further work.