Development of mean wind retrieval methodology for the Generalized Velocity Track Display

Since 1990s, the Ground-Based Velocity Track Display (GBVTD) – family of techniques, including the Generalized Velocity Track Display (GVTD), have been used to retrieve the kinematic structure of Tropical cyclones (TCs) using data from a single Doppler radar. This study builds on the GVTD formulation and proposes a single Doppler TC inner core mean wind retrieval technique, called GVTD-Mean Wind (GVTD-MW), that can improve the retrieved TC inner core structures and the understanding of TC intensity change. Results from analytical wind field experiments demonstrate that GVTD-MW can estimate mean wind speed and direction, with errors below 10% and 6°, respectively. GVTD-MW estimated mean winds are not sensitive to magnitude and direction of the along-beam mean wind component, vortex size, and uncertainty of the TC center. GVTD-MW was applied to Typhoon Nock-Ten (2004) and Typhoon Koinu (2023). For Nock-Ten, the significant cross-beam mean wind component enabled GVTD-MW to reduce the retrieval errors compared to GVTD. Consequently, the root mean square error (RMSE) for the entire volume decreased from 8.8 m s⁻¹ (GVTD) to 7.6 m s⁻¹ (GVTD-MW) when compared with radar observations. For Koinu, where the cross-beam mean winds were much smaller than those in Nock-Ten, GVTD-MW also improved the accuracy of storm structure retrieval. These findings demonstrate the characteristics and impacts of GVTD-MW in improving the TC structures from single-Doppler radar observations.