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the case of small-scale convective phenomena. Moreover non-precipitation echoes, such as
ground clutter, are often characterized by high variability that differs from that for
stratiform precipitation echoes. Spatial variability can be quantified as 3-D reflectivity
gradient (Friedrich & Hagen, 2004) or standard deviation in a certain spatial grid (Szturc et
al., 2011) and should be taken into account in quality index determination.
4.8 Total quality index
Computation of the total quality index QI is the final step in estimation of radar volume data
quality. If the individual quality indices QI i characterizing data quality are quantitatively
determined, then the total quality index QI is a result of all the individual values QI i
employing one of the formulas 2a - 2c.
Each elevation of raw reflectivity volume can be compared with final corrected field. A set
of such data for the lowest elevation is presented in Fig. 2. In this Figure a strong impact of
spike echoes is observed for Legionowo radar whereas ground clutter and related blockage
on data from Pastewnik radar is evident. Both radars are included in Polish radar network
POLRAD (Szturc & Dziewit, 2005).
Legionowo radar
Pastewnik radar
Fig. 2. Example of influence of all correction algorithms for the lowest elevation (0.5°): a) raw
data Z (in dBZ); b) corrected data Z ; c) total quality index QI (the left image for Legionowo
radar, 10.05.2010, 15:30 UTC, the right for Pastewnik radar, 5.05.2010, 18:00 UTC; distance to
radar up to 250 km). The panels represent range ( y -axis) vs. azimuth ( x -axis) displays.
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