Contributions of acoustic echo sounding to atmospheric research and services

This paper reviews briefly the first few years of acoustic remote sensing that followed the introduction of the echosonde in 1966, and then surveys in more detail many aspects of recent developments in acoustic echo sounding. The early, qualitative, facsimile recordings have now been supplemented by attempts to make the echosonde data quantitative. This has involved careful comparison of data from calibrated sounders and instrumented meteorlogical towers. Evidence is presented supporting the claim that echosondes can supplement the facsimile records with height profiles of mean wind speed and direction, as well as profiles of the structure constant of velocity Cv and temperature CT. The former permits derivation of the height profiles of the turbulent energy dissipation rate ε and the latter the measurement of height profiles of the structure constant of optical refractive index Cn. Various realizations of Doppler echosondes are presented, together with an echosonde interferometer which may offer promise of measuring atmospheric temperature profiles. Some future directions for acoustic echo-sounding developments are summarized.