Postset beam steering and interferometer applications of VHF radars to study winds, waves, and turbulence in the lower and middle atmosphere

Abstract

Spaced antenna VHF radar measurements are utilized for the postset beam steering technique and for interferometer applications to study winds, waves, and turbulence in the stratosphere and mesosphere. Following a brief description of the basic instrumental setup and the off‐line analysis method, some results are presented which demonstrate the consistency and applicability of these methods. Vertical velocity oscillations due to gravity waves are analyzed by means of the cross‐spectrum technique. It is shown that phase differences of gravity wave oscillations, measured between vertical and two opposite, off‐vertical postset beams, change their sign when the beam is swung back and forth. The same features of change of velocity sign are noticed when the mean wind is observed. The mean wind deduced with the postset beam steering technique is similar to the wind deduced with the spaced antenna drift technique and the independent radiosonde winds. Taking these results as justification for the applicability and feasibility of the postset beam steering method, the total wave vector and the intrinsic angular frequency of gravity waves in the stratosphere are deduced. Reasonable arguments are discussed to support the suggestion that these waves were generated in lower stratosphere wind shear regions and were attenuated little when propagating up to the middle stratosphere. Turbulence blobs in the mesosphere are tracked with the interferometer technique. It is shown that these blobs moved horizontally as well as vertically, a feature which cannot unequivocally be detected with conventional Doppler methods.