Single-Doppler Velocity Retrieval of the Wind Field in a Tornadic Supercell Using Data From a Mobile, Phased-Array, Doppler Radar

A 3DVar least-square type single-Doppler velocity retrieval (SDVD) algorithm is utilized to retrieve the wind field of a tornadic supercell during VORTEX2 in Goshen County, WY on 5 June 2009, using the data collected by a mobile, phased-array, Doppler radar (MWR-05XP) with very high temporal resolution (6 s). The quality of the SDVR analyses is evaluated by dual-Doppler syntheses using data collected by two mobile Doppler radars (DOW6 and DOW7). A comparison between the SDVR analyses and dual-Doppler syntheses confirms the conclusion reached by an earlier theoretical analysis that due to the temporally discrete nature of the radar data, the wind speed retrieved by single-Doppler radar is always underestimated. This underestimate occurs more significantly for the azimuthal (cross-beam) wind component rather than the radial (along-beam) component. However, the underestimate can be mitigated by increasing the temporal resolution of the radar data. When the radar data are collected at a sufficiently high rate, the azimuthal wind component may be overestimated.

Even with data from a rapid-scan, phased-array, Doppler radar, our study indicates that it is still necessary to calculate the SDVR in an optimal moving frame of reference. Finally, the robustness of the SDVR algorithm is demonstrated. Even with a temporal resolution (2 min) much lower than that of the phased-array radar, the cyclonic flow structure in the hook-echo region can still be retrieved through SDVR using radar data observed by DOW6 and DOW7, respectively. An explanation for the difference between the retrievals from DOW6 and DOW7 is given.