# Doppler velocity

From AMS Glossary

## Doppler velocity

The radial component of the velocity vector of a scattering object as observed by a remote sensor, such as a Doppler radar or Doppler lidar.

If

**V**denotes the velocity vector, then the radial component,*v*_{r}, is defined by the dot product, , where**r**is a unit vector in the pointing direction of the radar or lidar. By this definition, the Doppler velocity is positive for motion away from the radar. For distributed targets, the term Doppler velocity often refers to the mean Doppler velocity in the Doppler spectrum. Interpretation of the Doppler velocity depends on the viewing geometry and the kind of target. Clear-air echoes are assumed to move with the wind, so that the Doppler velocity measured at a given location in the atmosphere is equal to the radial component of the wind at that location. Precipitation falls relative to the air, so that the Doppler velocity of a precipitation target is assumed to be the sum of the radial velocity component of the precipitation terminal fall velocity and the radial component of the air motion.*See also*Doppler frequency shift, Doppler spectral moments, Doppler spectrum.