VAD and Dual-Doppler Analysis of Wind Fields from HIWRAP Observations During GRIP

A new airborne dual-wavelength Doppler radar, High-Altitude Imaging Wind and Rain Airborne Profiler (HIWRAP), has been developed at NASA Goddard Space Flight Center. Unlike the ER-2 Doppler radar (EDOP), which has fixed antennas, HIWRAP scans downward conically with two different elevation angles. The conical scanning capability of HIWRAP greatly extends the capability of EDOP for estimating three-dimensional wind field inside the storm. HIWRAP flew for the first time during NASA GRIP field experiment. In this study, we applied VAD analysis to HIWRAP data for wind retrievals assuming that horizontal wind fields are linear within the VAD circle and vertical wind is constant at each range gate. This assumption is reasonable for stratiform rain. For hurricane inner core and its vicinity, Dual-Doppler (DD) analysis should be used. The results show that in the stratiform region, the along-track winds from both approaches agree in general. Also the cross-track wind from VAD analysis is consistent with cyclonic rotation of the storm. Future work will include estimating ‘open circle' uncertainty for VAD analysis and determining cross-track wind using dual – Doppler analysis.