Analysis and simulation of phase coherent acdar sounding measurements

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 equiphase 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 CT2 and CV2 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.