USING A X-BAND WEATHER RADAR FOR AN URBAN AREA EARLY WARNING SYSTEM AND THE STUDY OF PRECIPITATION DYNAMICS.

Abstract

The development and availability of X-band radar instruments occurred in the last years, provides the scientific community of an important tool for the study, the characterization and the operational usage of detailed precipitation information. The hydrology laboratory of the Department of Civil, Environmental, Aerospace Engineering, and Materials (DICAM) at the University of Palermo, has installed a X-band weather radar in the urban area of Palermo (Italy) along with a set of advanced auxiliary instruments that help on exploiting the precipitation information. A raingauge network of 18 tipping bucket gauges spread over the observed area is available for the calibration of precipitation maps provided by the radar. Moreover a weight raingauge, an optical disdrometer, and a weather station are installed in a monitoring site. The information provided by these devices can be combined in order to integrate different data and correct errors. The disdrometer is used to estimate the drop size distribution (DSD) that results being directly linked to the parameters used for the transformation of radar reflectivity to precipitation estimates. Moreover, disdrometer observations can be used to classify the precipitation events. The comparison among traditional tipping-bucket gauges, weight-based raingauge, and disdrometer highlights possible issues related to instrumental errors affecting tipping-bucket gauges. Eventually, the weather station provides other different climatic variables that can be useful to interpret and analyze the rainfall events and to better characterize the same events. Radar precipitation estimates with high temporal and spatial resolutions, can be effectively used for supporting flood forecast analyses. Such an implementation is nowadays explored for different urban areas documented in the literature. In this study, observations from the radar and other sensors are embedded in an integrated early warning system able to provide warning related to possible flood in the urban area of Palermo.