Weighing gauges measurement errors and the design rainfall for urban scale applications

Investigation of the accuracy and precision of a modern Weighing Gauge (WG) under non steady-state reference flowrate conditions is addressed as the first objective of the present work. The preliminary development and validation of the laboratory equipment for the generation of variable time step reference flowrates is shown. The generator is characterized by a sufficiently short time response with respect to the expected weighing gauge behavior in order to ensure effective comparison of the measured vs. reference flowrates at very high resolution in time. Preliminary tests were con-ducted on the WG instrument by imposing different generation conditions: a finite step and a double step flowrate generation. The main goal of this initial phase was to characterize the time varying response of the instrument also providing an interpretation based on the dynamic system theory. The second part of the work was devoted to the simulation of biased WG time series under non-steady flowrates with a time resolution of one minute. The internal structure and variability of the generated events was based on 22 years of one-minute RI observations recorded at the meteorological station of Villa Cambiaso (University of Genoa). The influence of the measurement accuracy on the relevant extreme events statistics was analyzed by comparing the original intensity-duration-frequency (IDF) curves with those obtained after the simulation.