A new dealiasing method for Doppler velocity data quality control

The previously developed three-step dealiasing algorithm (Gong et al., 2003, JTech) in the radar data quality control package for radar data assimilation applications at the National Centers of Environmental Prediction has been upgraded recently in three major aspects. First, a new alias-robust VAD technique is used in place of the modified VAD method (Tabary et al., 2001, JTech) for the preliminary reference check in the first step. In this new alias-robust VAD technique, the effect of aliasing is mimicked by an aliasing operator and formulated into the costfunction, so the VAD analysis can be applied to raw aliased radial-velocity observations, although the minimization problem for the VAD fitting is complicated by the multiple local minima caused by the zigzag-discontinuities of the aliasing operator. Second, the refined reference check in the second step is bypassed. Third, the point-to-point continuity check in the third step is replaced by a cluster-to-point check procedure. The upgraded method has been tested extensively with aliased radial-velocity observations collected under various weather conditions. Examples will be presented at the conference to show the greatly improved performances and robustness of the upgraded method.