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| Titel |
Statistical analysis and modelling of weather radar beam propagation conditions in the Po Valley (Italy) |
| VerfasserIn |
A. Fornasiero, P. P. Alberoni, J. Bech |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1561-8633
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| Digitales Dokument |
URL |
| Erschienen |
In: Natural Hazards and Earth System Science ; 6, no. 2 ; Nr. 6, no. 2 (2006-05-08), S.303-314 |
| Datensatznummer |
250003406
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| Publikation (Nr.) |
 copernicus.org/nhess-6-303-2006.pdf |
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| Zusammenfassung |
| Ground clutter caused by anomalous propagation (anaprop) can affect
seriously radar rain rate estimates, particularly in fully automatic radar
processing systems, and, if not filtered, can produce frequent false alarms.
A statistical study of anomalous propagation detected from two operational
C-band radars in the northern Italian region of Emilia Romagna is discussed,
paying particular attention to its diurnal and seasonal variability. The
analysis shows a high incidence of anaprop in summer, mainly in the morning
and evening, due to the humid and hot summer climate of the Po Valley,
particularly in the coastal zone. Thereafter, a comparison between different
techniques and datasets to retrieve the vertical profile of the refractive
index gradient in the boundary layer is also presented. In particular, their
capability to detect anomalous propagation conditions is compared.
Furthermore, beam path trajectories are simulated using a multilayer
ray-tracing model and the influence of the propagation conditions on the
beam trajectory and shape is examined. High resolution radiosounding data
are identified as the best available dataset to reproduce accurately the
local propagation conditions, while lower resolution standard TEMP data
suffers from interpolation degradation and Numerical Weather Prediction
model data (Lokal Model) are able to retrieve a tendency to superrefraction
but not to detect ducting conditions. Observing the ray tracing of the
centre, lower and upper limits of the radar antenna 3-dB half-power main
beam lobe it is concluded that ducting layers produce a change in the
measured volume and in the power distribution that can lead to an additional
error in the reflectivity estimate and, subsequently, in the estimated
rainfall rate. |
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