An analysis of drought in Italy in the last fifty years

In this paper the authors present a study of drought occurrence over Italy. The NCEP/NCAR reanalysis precipitation rates covering the period from 1948 to 2000 were used to assess drought over the area in question. The analysis is based on the Standardized Precipitation Index (SPI), which has been proposed as an indicator of drought occurrence. The index relies on the knowledge of the precipitation field only, therefore, it may be readily computed from the data. A Principal Component Analysis (PCA) of the resulting fields reveals a downward trend for the index over the area considered. It implies that drought conditions have been in the recent past more frequent and extended, within the region, over larger areas. Moreover. the temporal behaviours of the principal component scores show few long-term periodicities.