Turbulent contributions to the echo-signal recorded by a monostatic sodar

For several decades, sodars have been widely used in many countries for studies of the atmospheric boundary layer. It is a common practice to retrieve the structure parameter of temperature fluctuations in the atmosphere from the echo-signal recorded by a monostatic sodar. This practice is based on the standard scattering theory result that the echo-signal is due to sound scattering by temperature fluctuations only while velocity fluctuations do not contribute to the echo-signal. In this paper, we consider a new theory of temperature and velocity contributions to the echo-signal recorded by a monostatic sodar. This new theory accounts for sound refraction in a stratified moving atmosphere while the standard theory does not. It follows from the new theory that, for moderate to strong wind conditions, velocity fluctuations can contribute significantly or even dominate the sodar's echo-signal. In these cases, the common practice of retrieving profiles of temperature fluctuations by monostatic sodars leads to significant errors.