The occurrence of extreme rainfall events, especially the ones of short duration, often causes extensive damages in densely populated regions; in flat urban areas, the most frequent hazardous phenomenon linked to brief and intense rainfall is the urban flooding, which is due to the inadequate capacity of urban sewage system to drain high amount of water in a short time. Successful monitoring of extreme events and forecasting of urban floods requires accurate precipitation estimation because of the complex hydrologic characteristics of the urban environment. In order to do this estimation, we focused on the metropolitan area of Turin, finding the extreme events and their thresholds, obtaining a climatic characterization of the area and identifying some case study. To thoroughly analyze these events we used both a C-band polarimetric Doppler weather radar and a dense network made by tens of tipping-bucket rain gauges, which are installed and operated by ARPA Piemonte (the regional agency for environmental protection). Thanks to this instrumentation, we have compared radar observations with ground measurements given by rain gauges during every single event. In order to reduce uncertainties, biases and errors between the two, we have applied on the radar data a common statistical reflectivity / rainfall rate (Z-R) relation, correcting it with the spatialization information obtained by the gauges with a very simple method that permits to reconstruct the rainfall field with a good accuracy. As we are interested in intense precipitation, the main objective of this study is to evaluate the performances of the radar with our adjustment technique that is able to reproduce properly observed maximum rainfall intensities on hourly basis.
Analysis of extreme rainfall events in the metropolitan area of Turin with weather radar and a dense rain gauges network
GUENZI, DIEGO;ACQUAOTTA, FIORELLA;Alice Baronetti;FRATIANNI, SIMONA;
2015-01-01
Abstract
The occurrence of extreme rainfall events, especially the ones of short duration, often causes extensive damages in densely populated regions; in flat urban areas, the most frequent hazardous phenomenon linked to brief and intense rainfall is the urban flooding, which is due to the inadequate capacity of urban sewage system to drain high amount of water in a short time. Successful monitoring of extreme events and forecasting of urban floods requires accurate precipitation estimation because of the complex hydrologic characteristics of the urban environment. In order to do this estimation, we focused on the metropolitan area of Turin, finding the extreme events and their thresholds, obtaining a climatic characterization of the area and identifying some case study. To thoroughly analyze these events we used both a C-band polarimetric Doppler weather radar and a dense network made by tens of tipping-bucket rain gauges, which are installed and operated by ARPA Piemonte (the regional agency for environmental protection). Thanks to this instrumentation, we have compared radar observations with ground measurements given by rain gauges during every single event. In order to reduce uncertainties, biases and errors between the two, we have applied on the radar data a common statistical reflectivity / rainfall rate (Z-R) relation, correcting it with the spatialization information obtained by the gauges with a very simple method that permits to reconstruct the rainfall field with a good accuracy. As we are interested in intense precipitation, the main objective of this study is to evaluate the performances of the radar with our adjustment technique that is able to reproduce properly observed maximum rainfall intensities on hourly basis.
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