Analysis and simulation of phase coherent acdar sounding measurements

Abstract

The phase surface geometry and its dependence upon system and atmospheric parameters for both monostatic and bistatic acdar sounders is discussed. The observed Doppler frequency shift is shown to be a consequence of the motion with respect to the equipbase surfaces of many distributed atmospheric scatterers. Because acdar measured average Doppler frequencies,and Doppler spectra are integral functions of system-related and atmospheric structure-dependent weighting functions, application of simple models that assume signal scattering only along the antenna beam axis may result in significant wind velocity measurement errors. It is further shown that accurate quantitative estimates of Cr: and Cv •' for thin turbulent layers require detailed analysis of the bistatic acdar common volume. Two techniques, based on distributed scatterers and random phasors, respectively, are used for simulating acdar signal phase and amplitude fluctuations.

A method for measurement of temperature profiles in inversions from refractive transmission of sound

“…The amplitude of received acdar signals depends upon the intensity of scattering or partial reflection of sound in regions of turbulent temperature and wind fluctuations. The altitude of a scatterin• region is determined by using the elapsed signal travel time, and atmospheric velocities are inferred from the properties of the Doppler spectrum of the received signal [see, e.g., Brown, .1972;Brown and Clifford, 1973;Thomson and Coulter, 1974].…”