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<br />spread. The trace-light results were good for
<br />identifying unsuppressed ground clutter. The wide
<br />spread results identified pixels of decreased
<br />accumulations having excessive suppression
<br />("holes" in pattern) and occultation problems
<br />(radial bands, seen at the top offigure 8). The
<br />ASCII formatted hybrid scan file could then be
<br />edited by hand to correct the problems. Pro-
<br />cedures for hand editing of the occultation file
<br />have not been developed.
<br />
<br />It was also noticed that "accumulations"
<br />sometimes had anomalous propagation (AP)
<br />during clear weather. Protection against AP,
<br />present in the PPS (Precipitation Preprocessing
<br />Subsystem), is not used in the SAA because AP is
<br />rarely a problem during snow events.
<br />
<br />7.3 Vertical Profile of Reflectivity
<br />
<br />Arlin Super, the former manager of the project,
<br />and I have repeatedly expressed our opinion that a
<br />major contribution to the SAA would be to take
<br />into account the vertical profile of reflectivity or of
<br />precipitation. However, it was never in
<br />Reclamation's scope of work to do so, even though
<br />many of our studies documented the need. To
<br />study the virga contamination problem, an
<br />experimental SAA supplement was developed to
<br />visualize the VPR. The coding changes are
<br />presented in appendix A. For each hour, the
<br />algorithm accumulates (at 0.1 km vertical
<br />resolution, 0 to 5 km in altitude above the radar) a
<br />cumulative percent of observed reflectivities at
<br />5 dBZ resolution. The output is a simple 8-bit
<br />array which must be imported into separate image
<br />processing software and annotated there.
<br />
<br />Figure 7a.-Vertical profiles for 10 November 1998. Figures 7 a-e give vertical profile examples, in the
<br />same style as figure 1, for 10, 11, 16, 18, and 19,
<br />November 1998, for five radars in the Dakotas and Minnesota. From left to right, they are KBIS, KABR,
<br />KMVX, KMPX, KDLH. On 10-11 November, a large snow storm affected the region, moving in from the
<br />southwest. Figure 7a shows profiles with strong vertical gradients, with strongest reflectivities near the
<br />ground, for KBIS and KABR on 10 November 1998. The other three radars show virga as the storm
<br />nears, later transforming to the precipitation graC~ent. KMPX and KDLH show some bright band effects
<br />at the top of figure Th. The end of the storm on the 11th shows a transition to shallow echoes.
<br />
<br />13
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