Airborne weather radar equipment, carried for detection of meteorological phenomena, is now well established as a standard equipment for most transport aircraft, and is even being specified for the larger executive types. It may be useful, therefore, to review the basic factors which influence the value of the information obtained and the progress made with equipment designs during the last decade.

Turbulence on its own cannot be detected by radar. The radar defines areas in which some form of precipitation is occurring, i.e. heavy rain, hail, ice crystals or snow. Of these, the areas in which large water droplets fall as heavy rain on the ground or exist in suspension in the cloud are of most interest, since they are inevitably associated with convective cloud formations. All other information relating to the possibility of turbulence, ice formations, hail, &c., must be deduced by the observer from his knowledge of the mechanism of such meteorological phenomena. However, it is clear that the radar must display information on large droplet type clouds only. The presentation of small water droplet clouds not associated with convective processes would serve only to confuse the picture.

The theory of reflections from meteorological phenomena is dealt with very thoroughly in the literature and here only the main conclusions will be summarized to show how the characteristics of a radar set affect the information produced.