A study of the multi-scale winds from radar retrieval for nowcasting

A new method to obtain multiple scale wind retrievals is proposed by using the Multi-scale Integrating Velocity Azimuth Process (MIVAP) method with different scale analysis sectors for nowcasting. The retrieved winds from the IVAP method with the large-scale analysis sectors are considered as the steering winds involving the systematic movement, while the small-scale internal motion vectors are estimated by the IVAP method with small scale analysis sectors. Then the retrieved winds with different scales are synthesized as the motion vectors for extrapolation nowcasting. Compared to the traditional Multi-scale Tracking Radar Echoes by Correlation (MTREC) methods, which rely on tracking radar echoes of a few time slices, the MIVAP method only needs the radar echo and radial velocity observations at the latest time. Comparison experiments based on a series of convective rainfall cases demonstrate that it is practical to apply the retrieved winds from the MIVAP method for nowcasting. The statistical verification tests show that extrapolated motion from the MIVAP method appears at the right of that from the MTREC method, and the speed of the former is faster than the latter. Nowcasting using the MTREC method performs better than that applying the MIVAP method in the few periods of the first 30 minutes, while the MIVAP method achieves better evaluation scores than the MTREC method after 30 minutes of forecasting periods, so the MIVAP method has a better performance than the MTREC on the whole.