Vaisala IRIS - Page 179

Atmospheric Waves
Produced at a variety of wavelengths and intensities. The shear values can be positive
or negative, depending on the nature of the wave and the "phase" being observed.
IRIS can compute the following types of basic shear values for the radial component of the
wind:
• Radial shear
Computed by dierencing the radial velocity in range. Positive values are for radial
velocity increasing (more away) with range. Divergence of the radial wind is positive.
• Azimuthal shear
Computed by dierencing the radial velocity in azimuth. Positive values are for radial
velocity increasing (more away) in the clockwise direction. This corresponds to positive
vorticity.
• Elevation shear
Computed by dierencing the radial velocity in elevation. Positive values are for radial
wind increasing (more away) with height.
In addition to the basic shears, combinations are computed using RMS values. For example,
the total combined shear magnitude is:
SQRT RAD
2
+ AZ
2
+ EL
2
Where RAD, AZ, and EL denote the basic shear values. Combined shears are positive.
Chapter 5 – Configuring and Scheduling Optional IRIS Products
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