A variational, pseudo-multiple Doppler radar analysis technique for mobile, ground-based radars

Mobile Doppler radar is one of the primary tools of research used in the study of severe thunderstorms, owing to its ability to sense remotely radial wind velocity very near features of interest, with high spatial resolution. However, the retreival of the full 3D wind field is non-trivial. To retrieve the full, 3D wind, assumptions (e.g., stationarity) and applicable external constraints (e.g., mass conservation) are often used.

The presentation will introduce a variational, ground-based, pseudo-multiple Doppler processing technique used to decompose time series of RHI velocity data into horizontal and vertical wind components. In this technique, RHI cross sections were taken normal to a dryline in clear air, with the radar platform in motion (hereon "rolling RHIs"), allowing for overlapping of rays. Therefore, points in the cross section domain received many looks from the radar at different angles. Assuming that the wind field associated with the dryline is stationary, the variational technique accurately recovered the components of motion in the plane of the cross section (u and w).

Results of observation system simulation experiments (OSSEs) with a LES of a highly sheared convective boundary layer highlight the strengths and shortcomings of the technique. The technique was applied to rolling RHIs taken on a retrograding dryline from 22 May 2002 during the International H2O Project. These data were obtained with the mobile 95 GHz UMass radar. The half-power beamwidth of this millimeter-wavelength radar was 0.18 degrees, allowing for very fine spatial resolution in the analysis.