Probable precipitation and reference evapotranspiration in São Paulo State, Brazil

Abstract

The study of rainfall (P) and reference evapotranspiration (ETo) are essential in areas with poor rainfall distribution. The aim of this study was to determine the parameters of the best-fit probability density function and to establish the probable ETo and P for the regular Grid of 0.25º x 0.25º, for São Paulo State, Brazil. The adherence of the probability density functions (pdf) of the ten-day values was obtained with the Kolmogorov-Smirnov test at 5% significance level. With the pdfs (Exponential, Gamma, Normal, Uniform and Triangular) that best fit P and ETo series in each ten-year period, the probable ten-day values of P at 75% probability (P 75% ) and ETo at 25% probability (ETo25%) were determined for each locality in the regular Grid. The Gamma and Normal pdfs, respectively, adjusted better by approximately 60% and 55% of the total adherence tests. The P 75% is well defined in the São Paulo State, being higher in the summer and spring-summer. The highest probabilities of ETo25% are in the Northern and Northwestern regions. The difference between "P75%-ETo25%" shows that higher water restrictions are expected mainly in the Northern and Northwestern regions during throughout the year, with winter being the most critical season.