It is a WSR 88-D product which shows the radar derived wind speeds at various heights. This radar product shows the wind speeds from 2,000 to 55,000 feet above the ground. VAD and EVAD (Extended VAD) are methods of guessing the large scale two-dimensional winds from one-dimensional radial velocity data. They are essentially multivariate regressions which fit a simple, large scale wind model to the observed winds. EVAD also estimates the large scale horizontal divergence and particle fall speed. See VWP.

Velocity Azimuth Display radar display on which mean radial velocity is plotted as a function of azimuth.

Velocity Azimuth Display. This WSR-88D radar product displays a graphical plot of mean radial velocity versus azimuth angle for a particular altitude. A best fit sine wave is overlaid on the plot of velocity points if a sufficient number (25) of data points exists. This wave is used to compute wind speed and direction for a specific height is symmetry and root mean square error thresholds are not exceeded. It is used to: 1) Check suspicious or missing wind data on the VAD Wind Profile (VWP); 2) Determine the potential strength of wind gusts; 3) Identify jets (low/mid/high level); and 4) Identify thermal advection patterns, vertical wind shear, depths of frontal surfaces, and the development of isentropic lift situations. The usefulness of this radar product is sometimes limited by lack of scatters at times.

Voice Activation Detection. Allows a data network carrying voice traffic to detect the absence of audio and conserve bandwidth by preventing the transmission of “silent packets” over the network. Most conversations include about 50% silence. VAD is also called “silence suppression”.

Voice Activated Dialing

Voice Activity Detector.

Ventricular Assistive Device

Ventricular Assist Device.

Vascular access device. VADs are catheters, or "ports", that are surgically placed in a large vein near the heart and stay in place for long periods of time. When a VAD is used, smaller, more easily irritated veins in the arms do not have to be accessed for chemotherapy.

Vente à Distance

vitamin A deficiency

Value-added distributor.