The monitoring, on probabilistic standardized basis, of the rainfall temporal variability by the Standardized Precipitation Index (SPI) model has been used by governmental programs in order to detect regions under severe rainfall deficit conditions. However, some conceptual issues, inherent to an index that uses only precipitation amounts as independent variable, tend to distance the SPI application of the agricultural interests. The aim of the work was to investigate the possibility of applying the drought monitoring concept, proposed by the SPI model, on ten-day period series of the difference between precipitation and potential evapotranspiration (P-EP). Based on meteorological data colleted in a weather station of Campinas, São Paulo State, Brazil, between 1948 and 2008, it was observed that the P-EP series fits well to the General Extreme Value Distribution (GEV). This fit has allowed the incorporation of the SPI concept on ten-day P-EP series and, therefore, the development of the standardized difference between precipitation and evapotranspiration index (IPP-ETP).
drought; general extreme value distribution; monitoring
