Doppler Weather Radar - METNET - India Meteorological Department

IRIS/Display Installed at remote workstations, the IRIS/Display system receives processed
product files or raw data over the network or from an archive, and uses them for display
purposes. It supports the basic product set. Remote control and monitoring are also supported.
A.3. Base Products received from Doppler Weather Radars
A.3.1. Reflectivity factor (Z)
This is the integral over the backscatter cross-section of the particles in a pulse volume. As per
the empirical relation, the reflectivity for the particles those are small as compared to the
wavelength the scatter cross-section will be D6, where D is the diameter of the particle. Radars
are calibrated in the way to give directly (assuming the dielectric constant of water) the
reflectivity factor from the received backscattered energy. The units for the reflectivity factor are
mm6 m-3 or in the logarithmic value it is denoted in dBZ, as indicated in the color scale in
following Figure A.5
Figure A.5. Reflectivity factor (Z)
A.3.2. Doppler velocity (V)
Doppler velocity is reflectivity-weighted average velocity of targets in the pulse volume and
determined by phase measurements from a large number of successive pulses. This is also called
radial velocity and gives only the radial component of the velocity vector. It is generally assumed
that raindrops and other particles are advected with the wind and have no own motion except
their falling velocity. A PPI picture of radial velocity is shown below in Figure A.6.
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