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 VM; however, HVVP is potentially limited by the unknown accuracy of empirical assumptions used to deduce the modified Rankine-combined vortex exponent X-T. By combing the GBVTD with HVVP techniques, this study proposes a modified GBVTD method (MGBVTD) to objectively deduce X-T from the GBVTD technique and provide amore accurate estimation of V-M and V-T0 via an iterative procedure to reach converged V-T0 and cross-beam component 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 VM is within 2ms(-1) of reality. MGBVTD was applied to Hurricane Bret (1999) whose inner core was captured simultaneously by two Weather Surveillance Radar-1988 Doppler (WSR-88D) instruments. The MGBVTD-retrieved cross-beam component of VM 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). The mean difference in theMGBVTD-retrieved V-T0 from the two radars is similar to 2ms(-1), which is significantly smaller than that resolved in GBVTD retrievals (similar to 5ms(-1)).