Performance of two velocity dealiasing algorithms on Terminal Doppler Weather Radar data

The Supplemental Product Generator (SPG) has been developed to ingest Terminal Doppler Weather Radar (TDWR) base data and provide this data, along with algorithm products, to National Weather Service forecast offices. Since the TDWR is a 5 cm wavelength radar, it typically operates at lower Nyquist velocities than the WSR-88D. In weather situations involving high wind speeds and/or wind shear regions (e.g., gust fronts associated with squall-lines), together with a TDWR scanning at a low Nyquist velocity, dealiasing errors are common. Sometimes, the errors are so extensive that it is very difficult to properly utilize the velocity data. Hence, improving the dealiasing capability of the SPG would greatly enhance the value of the TDWR velocity data. In pursuit of this goal, this project set out to compare the performance of the current SPG velocity dealiasing algorithm to a newly developed 2D multi-pass dealiasing algorithm (2DMPDA).

The performance comparison used data collected from the Baltimore/Washington TDWR site for 8 severe weather events. The scoring procedure was quantitative in nature, where elevation scans were given an initial score of 100, and “points” were subtracted for each dealiasing error observed. Test results indicate that the 2DMPDA generally did a superior job at dealiasing the TDWR velocity data compared to the current SPG dealiasing algorithm. The superior performance for the 2DMPDA occurred primarily at the two lowest elevation angles, and for Nyquist velocities <19 m/s. However, the 2DMPDA did not do as well as the SPG dealiasing algorithm with important severe weather signatures, such as mesocyclones. Hence, further testing is needed, along with perhaps additional algorithm development or adaptable parameter adjustments, before the 2DMPDA could be recommended as a replacement for the current SPG dealiasing algorithm.