Satellite and Ground Based Observations for Extreme Events Interpretation: One Application on Precipitation Anomalies and Floods in the South of Italy

The synergic use of satellite and ground based observations could help in order to extend our present capabilities in the interpretation of extreme events related to rainfall. Higher coverage and low cost offered by satellite observations could be usefully related to sparse measurements obtained, with higher accuracy, from ground based stations, provided that a suitable merging and interpretative scheme has been defined. In this work several satellite-based products, together with ground based observations, have been used in order to obtain a complete description of concurrent events and preparing conditions which transformed a severe, but restricted in space and time, precipitation event in a catastrophic flooding occurred last year in the South of Italy. Six people dead and serious damage were consequent to the events observed on the 14 October 1996 in Crotone. Five hours of precipitation, with return period nor greater than 50-60 years, were observed together with runoff at higher recurrence time. Soil features (lithology and land cover) combined with antecedent precipitation events have been considered as possible preparing conditions. Antecedent Precipitation Index (API) and Microwave Polarization Difference index (MPDI) obtained from SSM/I (Special Sensor Microwave Imager on board DMSP platforms) data have been used in order to characterize soil humidity, TM (Thematic Mapper on board Landsat satellites) data were used in order to describe land cover. Data coming from Advanced Very High Resolution Radiometer (AVHRR) and High Resolution Infrared Sounder (HIRS), both flying on NOAA satellites, have been used, together with SSM/I retrieval, in order to describe precipitable water (i.e. total water vapor columnar content) field before, during and after the event as well to recognize meteorological features at the synoptic scale. Comparison with ground-based observations has been performed and improvements, coming from the synergic use of satellite observations, discussed in the context of a possible nowcasting scheme.