Geoscience Reference
In-Depth Information
The relationship between surface refractivity and the vertical refractivity gradient for the first
kilometre was investigated during the sixties for data collected in the UK (Lane, 1961) and the
US (Bean and Dutton, 1968). In both cases a high correlation was found for monthly averages
of both magnitudes. For the data set collected in Barcelona, a correlation of 0.9745 was found.
3.3 Anaprop echo variability
Quality control procedures for QPE have traditionally dealt with anaprop and, in general,
clutter echoes (see, for example, Anderson et al., 1997; Archibald, 2000; da Silveira and Holt,
1997; Fulton et al., 1998; Joss and Lee, 1995; Kitchen et al., 1994; Sánchez-Diezma et al., 2001,
Steiner and Smith, 2002; Szturc et al., in this volume; and Villarini and Krajewski, 2010,
among others).
Fornasiero et al. (2006a, 2006b), studied AP echoes occurrence in two radars in the Po Valley,
Italy, with a methodology developed by Alberoni et al. (2001). With a three year dataset, they
examined the seasonal variability of AP echoes in the diurnal cycle (Fig. 9).
Fig. 9. Mean percentage of anaprop clutter detected. The average is calculated for each hour
during the time range 1 January 2002-31 December 2004 for San Pietro Capofiume (a) and
for Gattatico radar (b) in the Po Valley, Italy (adapted from Fornasiero et al. 2006a).
They found that in the warm season there were more AP echoes (reaching nearly 20% of the
time) with a maximum in the late evening and a secondary maximum at noon, probably
associated with local circulations such as sea breeze. In winter the variability was much
lower and AP echoes were generally below 5%. These results were helpful to characterize
the incidence of AP in precipitation estimates and to design an adequate quality control
procedure.
4. Radar beam blockage and propagation conditions
In this section the effect of propagation conditions on beam blockage corrections is
described. This type of correction is a classical post-processing step applied to radar
reflectivity measurements in order to obtain quantitative precipitation estimates in hilly
terrain. A particular implementation of this correction developed during the COST 717
action (Rossa 2000) is described.
