Rainfall monitoring systems over an urban area: the city of Rome

In small catchments a very high space-time rainfall resolution is needed in order to obtain, with sufficient accuracy, flash flood nowcasting as well as monitoring of sewer systems. In this light, a radar meteorology campaign was conducted during the fall of 2001, over the city of Rome (Italy), using measurements collected by the polarimetric Doppler radar Polar 55C located in the south-east of the city at a distance of 15 km from the downtown and by a network consisting of 32 tipping bucket raingauges. A comparative analysis of the rainfall fields obtained using two interpolation methods (inverse-distance and kriging) with those obtained using radar rainfall measurements was performed. The overall performance of the different methods was evaluated using objective functions. Errors depending on the gauge density were weighed by changing the number of raingauges considered in the reconstructed rainfall fields.