Second-Order Doppler Shift of RASS Echoes

Abstract

High-resolution measurements of the frequency shift of radio acoustic sounding system echoes show small (≤10?3) systematic deviations from values that are expected according to basic theory. It is shown that these deviations can be explained by two successive scattering processes: 1) scattering of acoustic waves from atmospheric turbulent (acoustic) refractive-index structures, and 2) scattering of radar waves from that component of the scattered acoustic field that satisfies the condition for specular reflection. An expression for the frequency shift is derived, which agrees with the theory of Lataitis for the case of ?strong? turbulence. Preliminary experimental observations are presented, which support this analysis.