Radial Velocity

The radial velocity (VR) is a two dimensional representation of the radial velocity data. It is derived from the Doppler scan. It is based on the corrected radar data. In the signal processor, the I,Q or engineering data is transformed to a velocity spectrum. The spectrum is edited to removed ground clutter. It is transformed back to the time domain and Pulse Pair algorithms are used to compute the radial velocity, spectral width and signal quality index. There is an SQI filter on the radial velocity data applied in the signal processor. It is possible to have radial velocity data and not reflectivity data due to different filters being applied. For operational interpretation, it is confusing to have valid data on one image and not on the corresponding reflectivity or radial velocity image, so there is a requirement when producing the VR product that there be valid reflectivity data at the same radar bin. Note that a CSR of about 18 dBZ is used to filter the reflectivity data. This is a basic data display and units of m/s are traditionally used.

For dual PRF data, only the extended radial velocity is available. Alternating rays are used to compute the dual PRF estimate. The PRFs could be any order for each "dwell" or "ray" so the result could be unfolded to either the low or high PRF data. There is an bit in the data stream that tells which PRF is used. One of the side effects of the dual PRF unfolding scheme is errors due to violation of the simultaneity assumption of the data collection in time and space. So a despiking algorithm is applied. 

 
Sample radial velocity image.