Adaptive beamforming technique for accurate vertical wind measurements with multichannel MST radar

Abstract

Aspect-sensitive backscattering of the atmosphere causes a small error in an effective line-of-sight direction in vertical beam observations leading to a serious degradation of vertical wind estimates due to contamination by horizontal wind components. An adaptive beamforming technique for a multichannel mesosphere-stratosphere- troposphere (MST) radar is presented, which makes it possible to measure the vertical wind velocity with higher accuracy by adaptively generating a countersteered reception beam against an off-vertically shifted echo pattern. The technique employs the norm-constrained direction-constrained minimization of power (NC-DCMP) algorithm, which provides not only robustness but also higher accuracy than the basic direction-constrained minimization of power algorithmin realistic conditions. Although the technique decreases the signal-to-noise ratio, the ratio is controlled and bound at a specified level by the norm constraint. In the case that a decrease of 23 dBis acceptable in a vertical beam observation, forwhich usually amuch higher signal-to-noise ratio is obtained than for oblique beams, the maximum contamination is suppressed to 1/10 even for themost imbalanced aspect sensitivity. © 2012 American Meteorological Society.