Quality Assessment of Weather Radar Wind Profiles during Bird Migration

Wind profiles from an operational C-band Doppler radar have been combined with data from a bird tracking radar to assess the wind profile quality during bird migration. The weather radar wind profiles ( WRWPs) are retrieved using the well-known volume velocity processing ( VVP) technique. The X-band bird radar performed range-height scans perpendicular to the main migration direction and bird densities were deduced by counting and normalizing the observed echoes. It is found that the radial velocity standard deviation ( sigma(r)) obtained from the VVP retrieval is a skillful indicator of bird migration. Using a threshold of 2 m s(-1) on sigma(r), more than 93% of the bird-contaminated wind vectors are rejected while over 70% of the true wind vectors are accepted correctly. For high bird migration densities the raw weather radar wind vectors have a positive speed bias of 8.6 +/- 3.8 m s(-1), while the quality-controlled wind vectors have a negligible speed bias. From the performance statistics against a limited area numerical weather prediction model, it is concluded that all ( significant) bird contamination is removed and that high-quality weather radar wind profiles can be obtained, even during the bird migration season.