Session 5.5 An automated 2-D multi-pass velocity dealiasing scheme

Tuesday, 5 October 2004: 5:30 PM
Jian Zhang, CIMMS/University of Oklahoma, Norman, OK; and S. wang

Presentation PDF (3.0 MB)

An automated and improved velocity dealiasing scheme has been developed to correct velocity fields when wind velocities are very large compared to the nyquist velocity. The existing operational WSR-88D velocity dealiasing scheme has difficulties correcting folded velocities when nyquist velocities are small and in regions near data voids.

The new multi-pass velocity dealiasing algorithm is based on the horizontal continuity of velocity fields. The algorithm first determines a set of reference radials and gates by finding the weakest wind region. Then from these reference radials and gates, the scheme checks continuities among adjacent gates and corrects for the velocity values with large differences that are close to 2*(nyquist velocity). Multiple passes of unfolding are performed and velocities identified as “folded” with low confidence in an earlier pass are not unfolded until a discontinuity is detected with high confidence at a subsequent pass. Utilizing over 100 case studies, the new velocity algorithm converges rapidly resulting in dealiased velocity fields typically obtainable in just 3 passes. The new velocity dealiasing scheme shows significant improvement over the current operational WSR-88D algorithm.

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