The Design and Operation of an Acoustic Radar

The history and theory of the acoustic radar are briefly reviewed. It is pointed out that scattering of sound by the atmosphere is produced by temperature and wind fluctuations, but that only temperature variations produce backscatter. Concepts for using the acoustic radar to measure profiles of temperature, wind, and humidity are discussed. A technique for measuring humidity profile using the relationship between attenuation of sound and absolute humidity is described. Design of the acoustic radar components is discussed with particular emphasis given to the problem of the antenna design. Some of the results of eight months of operation of the system are discussed. One case in which the acoustic radar was able to detect the passage of a thermal structure discontinuity not detectable by conventional observational and analysis techniques is described. It is concluded that the analog form of the data has great potential usefulness for continuously monitoring the thermal structure of the lower troposphere. Further measurement of wind and humidity profiles, and perhaps also the temperature profile to heights of a few thousand feet by means of the acoustic radar, seems feasible if the signal-to-noise ratio in the present system can be improved.