Velocity-azimuth display

From Glossary of Meteorology

velocity–azimuth display

(Abbreviated VAD.) A radar display of the mean Doppler velocity at a given range as a function of the azimuth angle as the radar antenna rotates through (usually) a complete 360° azimuth scan at a constant elevation angle.

Harmonic analysis of a VAD is used to determine spatially averaged kinematic properties of the wind field, namely, the wind speed and direction, the horizontal divergence, the horizontal deformation, and the orientation of the axis of dilatation. By repeating this process at many elevation angles or ranges, a vertical profile of the horizontal wind (VAD wind profile) above the radar site can be constructed.