Geoscience Reference
In-Depth Information
Fig. 5. The flow of the radar data to warning product is much the same in all systems. But
the contents of each stage can be different. Except for one system described in this
contribution, all the others require human decision-making at stage C before the warning
product is issued to the public. In the case of KONRAD (see section 6.10), the product goes
mainly to “sophisticated” users.
5.1 Data quality
Radar processing systems need quality controlled data. This can occur in a separate and
independent process. In some cases, it is part of the adjustments and corrections that need to
be made. Before the severe weather processing occurs (stage B in Fig. 5), it is assumed that
the data is free of anomalous propagation, ground clutter and biases in power are adjusted.
Second trip echoes and range folded may still be in the Doppler data (Joe 2009; Lakshmanan
et al, 2010; Lakshmanan et al, 2011).
In high shear environments the assumption that the radial velocities within a range volume
are uniform may not be satisfied (Holleman and Beekhuis 2003; Joe and May 2003). Fig 6ab
shows a simulated Doppler velocity spectrum (based on an example in Doviak and Zrnic,
1984) of a tornado contained within a single range volume. The spectrum is bi-modal and
the peaks at located at the speed of the radial components of the tornado. Normally it is uni-
modal and Gaussian in shape. Fig. 6cd show the measured spectrum given two different
Nyquist limits. The spectrum is aliased and overlaps with itself. The smaller the Nyquist
limit, the greater the overlap. In highly sheared regions, the velocity data is noisy and can be
non-sensical. The chapter on quantitative precipitation estimation addresses many of the
quality control issues.
