Dealiasing of radar Doppler velocities to improve wind estimations

Abstract

With its three beams in different directions, the Transportable Atmospheric RAdar system (TARA) can provide a wind field estimation. These estimations are inaccurate when the Doppler velocities in one or more of the three beams are aliased. Amongst different approaches to solve aliasing are a continuity check up to four dimensions, staggering PRT (Pulse Repetition Time) technique and a method using polarimetric information. The staggering PRT technique is not applicable, because it requires altering the radar system itself. For the main beam of TARA the method using polarimetric information is used, but for the offset beams nopolarimetric information is available. The research presented in this thesis focuses on the dealiasing of the offset beams using a continuity check in one dimension. The assumed correctly dealiased main beam is used as a reference to compare the offset beams with. The first step towards correct Doppler velocities is unfolding every individual Doppler spectrum. Then, a reference spectrum is searched for in the main beam. The first spectrum in the offset beam that is placed in the right Doppler velocity interval, is the one that is at the same height as the reference spectrum. From there on a continuity check is performed. First away from the radar and then towards the radar. Comparison is done by using the mean Doppler velocities of every Doppler spectrum. The algorithm proposed in this thesis shows significant improvement in performance, compared with the old algorithm. In case of very wide Doppler spectra, a large difference between the reference and the current spectrum and clutter, the algorithm can fail.