Vaisala IRIS - Optimizing SHEAR for Microburst Detection; Figure 64 B-Scan Space (PPI Surface)

Azimuth Shear Differencing
Azimuth
Range
Radial Shear Differencing
Figure 64 B-Scan Space (PPI surface)
The azimuth shear algorithm is analogous to the radial shear algorithm except that:
• Dierencing is performed from ray-to-ray at constant range.
• The azimuth filter length is specified in degrees.
• The final azimuth values are range normalized and corrected for the apparent azimuth
shear caused by the mean wind. The mean wind value is obtained from the VVP
algorithm. This correction is an optional step.
For information on the mean velocity correction, see Optimizing SHEAR for Microburst
Detection (page 182).
Shear Magnitude
After both the radial and azimuth shears have been obtained, the next step is to compute
the shear magnitude. This is the square root of the sum of the squares of the 2 shear values
(radial and azimuth) associated with each bin.
If only a single shear is selected (radial or azimuth), this step is skipped.
Convert to Cartesian and Optional Final Cartesian Smoothing
The conversion to Cartesian transforms the B-scan values of the shear magnitude to X-Y
coordinates.
The algorithm is identical to the PPI algorithm, which uses a last-in approach for both range
and azimuth filling. An optional 2D smoother with selectable length scale can be passed
over the data at this point.
5.6.2
Optimizing SHEAR for Microburst Detection
Accurate detection and timely reporting of microbursts in an air trac control environment
requires that the system be properly configured and optimized.
Vaisala recommends you work with a qualified consultant to assist with tuning and
evaluating the IRIS SHEAR algorithm, data acquisition, radar siting and warning reports.
IRIS Product and Display User Guide M211319EN-H
182 RESTRICTED