Zero Reference Height
Data Truncation Height
Reference Height
0
h
ref
h
max
h
0C
0 dB
S
i
S
r
D/2
I
0C
D/2
Region 1
Region 2
Region 3
Region 4
Figure 23 SRI Reflectivity Profile Example
The profile includes the following:
• Height h=0 corresponds to the Setup > Product Zero Reference Height.
This is typically set at either the nominal ground level or sea level.
• The max height corresponds to the Setup > Ingest Data Truncation Height.
• The reflectivity varies linearly in dBZ above and below the bright band.
Separate slopes are used above and below the bright band (S
r
for rain and S
i
for ice).
• The bright band starts at the 0°C level (h=h
0C
), has depth (D) and intensity (I), defined
as the intensity dierence between the peak and the intensity the rain would have at
the center of the bright band, that is, determined by the continuation of the rain slope
into the bright band.
The surface rainfall intensity at each pixel is calculated by finding the lowest clutter-free bin,
and bringing the measured reflectivity there down to reference level by making 2
corrections:
1. The correction for the beam weighted averaging.
2. The adjustment for the profile to obtain the reflectivity at the reference height.
The SRI product also supports using a terrain map to determine the height that that radar
beam is corrected to. See Format of Terrain Map File (page 81).
Convective Check Algorithm
In convective precipitation there is usually no detectable bright band or perhaps a very weak
one. This is thought to be caused by the types of particles near the melting level that are
typical of convective precipitation. These are usually heavily rimed snowflakes, graupel,
frozen drops (carried aloft), or hail. Since these particles tend to fall more rapidly than snow
aggregates, they do not contribute to a bright band in the same way as large wet snow
flakes falling at 1 m/s. That is, there is no convergence of large wet particles.
IRIS Product and Display User Guide M211319EN-H
72 RESTRICTED
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