Distortion of gravity wave spectra of imaging Doppler interferometry horizontal winds

We elsewhere suggest (Rastogi et al., this issue) that an analytic model for spectral distortion in the Doppler beam steering (DBS) horizontal wind estimates should also qualitatively hold for the imaging Doppler interferometry (IDI) and spaced antenna (SA) methods. Here we give further support for this suggestion through a statistical model for spectral distortion in the IDI horizontal wind estimates. In IDI the signals observed with a single or multiple receivers at ground are used to identify the locations and radial velocities of virtual atmospheric targets; wind components are then estimated by regression. The statistical model includes the effect of isotropic target configurations as a spatial filter on an isotropic ensemble of atmospheric gravity waves. It shows that the frequency spectrum of IDI horizontal wind estimates is enhanced beyond a knee, located at a ∼0.7-hour period in the upper mesosphere, and then drops near the buoyancy frequency. The occurrence of the knee and its location is similar to the spectral distortion in the DBS horizontal wind estimates modelled earlier.