Abstract
Piemonte region, in the north-western Italy, is characterized by complex orography and Mediterranean influence that often causes extreme rainfall event, during the warm season. Although the region is monitored by a dense gauge network (more than one gauge per 100 km2), the ground measurements are often inadequate to properly observe intense and highly variable precipitations. Polarimetric weather radars provide a unique way to monitor rainfall over wide areas, with the required spatial detail and temporal resolution. Nevertheless, most European weather radar networks are operating at C-band, which may seriously limit quantitative precipitation estimation in heavy rainfall due to relevant power signal attenuation. Phase measurements, unlike power measurements, are not affected by signal attenuation. For this reason, polarimetric radars, for which the differential phase shift measurements are available, provide an additional way in which to estimate precipitation, which is immune to signal attenuation. In this work differential phase based rainfall estimation techniques are applied to analyze two flash-floods: the first one occurred on the Ligurian Apennines on 16 August 2006 and the second occurred on 13 September 2008, causing rain accumulations above 270 mm in few hours.
Highlights
The study area, located in north-western Italy, is characterized by complex orographyIt is bordered on the north and west side by the Alps, with peaks of around 3,000 meters above sea level
Polarimetric radars, for which the differential phase shift measurements are available, provide an additional way to estimate precipitation, which is immune to signal attenuation
Wide areas are nowadays monitored by dense rain gauge networks, flash flood, sudden severe and localized precipitation, can still be missed
Summary
The study area, located in north-western Italy, is characterized by complex orography. The increasing of rain drops with increasing rainfall intensity causes horizontally polarized radar waves to suffer a higher propagation phase shift with respect to the vertical polarized waves [3] For this reason, polarimetric radars, for which the differential phase shift measurements (the difference between phase shift at horizontal and vertical polarization) are available, provide an additional way to estimate precipitation, which is immune to signal attenuation. The region is monitored by a dense ground network, composed of over 400 gauges, two C-Band polarimetric and Doppler radars, near Torino in Bric della Croce at 770 m.s.l. and near Savona in. Polarimetric radar measurements were de-cluttered by fuzzy logic algorithm [4,5] and interpolated on a 500 m resolution UTM (Universal Transverse Mercator)European Datum 1950 Cartesian grid (UTM ED50)
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