Thursday, 7 August 2003
A Solution for Range-Velocity Ambiguity using Hybrid Multi-PRF Dealiasing Algorithm
To solve range-velocity ambiguity of meteorological Doppler radar, Hybrid Multi-PRF algorithm was developed and tested on observed Doppler velocity data. Hybrid Multi-PRF algorithm produces a Doppler velocity field with a higher unambiguous Doppler velocity from one or more Doppler velocity datasets observed at different PRFs comparing velocity to the plane fitting value around the data. The algorithm is more accurate and robust than previous methods in dealiasing Doppler velocities in strong wind shear or sparse data region, or with large random error. Applying the algorithm to Doppler velocity fields observed by "random phase processing with dual-PRF" and "relatively low PRF" solves both frequent data missing of the former observation in distant area from radar (second-trip echo region) and small unambiguous velocity of the latter observation.
The algorithm was tested on the datasets of the typhoon HALONG observed by the Meteorological Research Institute C-band Doppler radar on July 16, 2002, to achieve dealiased Doppler velocity field with observing range of 250km and unambiguous velocity of 53m/s. It was found that Doppler velocities were correctly dealiased in 90% of whole echo region including strong wind shear, although velocities were not determined in 10% of the echo region around where only one PRF was available. The result showed Hybrid Multi-PRF algorithm practically realized long range Doppler velocity observation with high unambiguous velocity. In the case of our C-band radar, the observing range was extended from 160km to 250km with the unambiguous velocity of 53m/s.