The improvement to the environmental wind and tropical cyclone circulation retrievals with the modified GBVTD (MGBVTD) technique

The ground-based velocity track display (GBVTD) was developed to deduce a three-dimensional primary circulation of landfalling tropical cyclones from single-Doppler radar data. However, the cross-beam component of the mean wind V_M cannot be resolved and is consequently aliased into the retrieved axisymmetric tangential wind V_T0. Recently, the development of the hurricane volume velocity processing method (HVVP) enabled the independent estimation of V_M; however, HVVP is potentially limited by the unknown accuracy of empirical assumptions used to deduce the modified Rankine-combined vortex exponent XT. By combing the GBVTD with HVVP techniques, this study proposes a modified GBVTD method (MGBVTD) to objectively deduce XT from theGBVTDtechnique and provide amore accurate estimation of V_M and V_T0 via an iterative procedure to reach converged V_T0 and cross-beamcomponent of V_M solutions. MGBVTD retains the strength of both algorithms but avoids their weaknesses. The results from idealized experiments demonstrate that the MGBVTD-retrieved cross-beam component of V_M is within 2ms^-1 of reality. MGBVTD was applied to Hurricane Bret (1999) whose inner core was captured simultaneously by twoWeather Surveillance Radar-1988 Doppler (WSR-88D) instruments. The MGBVTD-retrieved cross-beam component of V_M from single-Doppler radar data is very close to that from dual-Doppler radar synthesis using extended GBVTD (EGBVTD); their difference is less than 2ms^-1. Themean difference in theMGBVTD-retrieved V_T0 from the two radars is ~2ms21, which is significantly smaller than that resolved in GBVTD retrievals (~5ms^-1).