Chapter 6 ______________________________________________________ Processing Algorithms
VAISALA______________________________________________________________________ 233
search pattern is shown at the bottom of the previous figure. This
larger selection of alternate-PRF bins makes it more likely that the
algorithm will find the pairs of Low/High PRF data that are required
for unfolding.
2. The unfolded velocities are then subjected to the standard 3x3
filtering.
Dual PRF, Random Phase Processing
In random phase processing, the "seam" at the start of the second trip is
always problematic, since the transmitter main bang and nearby clutter will
virtually always wipe out the first few second trip range bins. At a constant
PRF, the second trip seam is always at the same range, but in dual PRF
random phase mode, the seam is different each ray. Thus thresholded bins
at the seam of the high PRF can be surrounded on either side by valid bins
taken at the low PRF. The 3x3 filter has the effect of interpolating the
reflectivity and width data over the bins at the 2nd trip seam. Velocity data
will also be filled-in using the nearest neighbor. Thus the 2D filter
mitigates much of the damage that is caused at the 2nd trip seam to make
a nearly seamless display.
6.5 Reflectivity Calibration
The calculation of reflectivity described in Section 6.3.3 Reflectivity on
page 215 required the calibration reflectivity dBZ
o
. This section describes
it's derivation. You can use the zauto utility to perform the calibration.
(refer to the IRIS/RDA Utilities Manual.)
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