Theory and Practice of Tropospheric Sounding by Radar

Studies of tropospheric sounding by pulsed radio waves have been extended from the original medium-frequency phase to include the use of modern high-powered, sharply beamed microwave radar systems. The apparent detection of discrete echoes from entire air-mass boundaries and from thick regions of relatively high values of dielectric gradient at vertical incidence is indicated by experimental results attained on medium frequencies during the period from 1935 to 1942. On certain occasions, the indicated heights embraced almost the entire troposphere. Sample results are illustrated. More recently, continuous photographic records have been made by vertical beam-sounding techniques which involved the use of modified SCR-584 and AN/CPS-1 (MEW) microwave radar systems. In addition to the familiar scattering reflections from raindrops, snowflakes, and ice particles from heights up to about 50,000 feet, continuous records of "dot," "line," and other unusual weak echo signals are obtained in some form at all times, up to heights of at least 30,000 feet, when sufficient power and sensitivity are available in the radar system. Samples of these photographic recordings are shown, and a simultaneous radiosonde plot is provided for comparison. References are cited to show additional supporting experimental evidence which seems to indicate more strongly that the origins of many of these echo patterns are in the fine structures of the dielectric transition layers of air-mass boundaries and airturbulence and mixing regions.