A model for monthly rainfall periodic regression analysis, of the southeast Atlantic basin, on Parana State

This study deals with the periodic regression analysis of the monthly total rainfall, for eight locations in the State of Parana, Brazil. Mathematical models which describe the course of this variable observing a period of tw elve months were applied. The analysis was developed by means of matrice al gebra and the expansion in Fourier series of a function f(t), periodic and defined for intervals. The original data were adjusted for 30-day months an d all harmonic components of the functions referring to each of the eight l ocations were determined. After testing for normality of the harmonic compo nents, an analysis of variance was made, which made it possible to identify the significant harmonic components which were chosen to make up part of t he regression equation corresponding to each location. These equations expl ain 89.56% up to 99.60% of the variation due to months, for the whole set o f studied locations. Probability for occurrence of a year in accordance to the model, in percentage, ranges from 14.19% to 68.42%, while probability f or occurrence of a year adjusted to mean, ranges from 0.02% to 1.87%.