Glossary
$IRIS_ROOT
Entry point of the IRIS/RDA install tree
AGC
Automatic Gain Control. The gain of the linear channel video signals is adjusted based
on an estimate of the next signal level. For example using the average power of the
last few pulses at that range.
Associated task
The task that is associated with a product generation. For example, a PPI product
requires an associated task that uses the PPI scan mode (Full or Sector).
BEAM product
Cartesian product similar to the Cross Section perpendicular to the radar which
displays data at a fixed range (or averaged over a range interval) on an azimuth vs.
elevation grid. This is useful for testing the antenna beam pattern when used with a
reference transmitter.
Bin
A single sample of weather data detected at a known direction, altitude, and distance
from the radar site. The radial size of a bin depends on decreases with distance, so
bins further from the radar site cover a larger area than nearby bins.
Bright band
Altitude range over which the falling snow is partially melted, but not completely
changed into rain. Wet snow and wet ice has a higher reflectivity than either dry snow
or rain, so it forms a band of stronger returns. The top of this band is called the Melting
Level or 0°C height.
CAPPI product
Constant Altitude Plan Position Indicator. A CAPPI is a horizontal slice through the
atmosphere at a given height. The positioning and orientation of the cross section is
arbitrary.
COMP product
Composite product combining a group of CAPPI, VIL, PPI, or TOPS products from
dierent radars together into one larger image.
Doppler spectrum width
The standard deviation of the Doppler spectrum in m/s. The spectrum width is a
measure of the shear and turbulence in the radar pulse volume at a given range. See
also Doppler velocity spectrum (page 103).
Doppler velocity (v)
Reflectivity-weighted average velocity of targets in the pulse volume. Determined by
phase measurements from a large number of successive pulses. It is assumed that
raindrops and other particles are advected with the wind and have no own motion
except their falling velocity. Also called radial velocity.
Doppler velocity spectrum
The spectrum of the power returned as a function of the Doppler velocity (towards or
away from the radar). The mean of the Doppler velocity spectrum is the mean velocity
computed by the signal processor. The standard deviation of the Doppler spectrum is
the spectrum width (in m/s).
Glossary
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