Bidecadal cycles in liquid precipitations in Brazil Original Research Article

Data on liquid precipitation in Brazil for three meteorological stations in Pelotas, Campinas, and Fortaleza from 1849 up to 2000 were considered. The stations span practically the entire latitude range of Brazil. Periodic analysis of the annual rainfall level in Pelotas and in Fortaleza shows a pronounced bidecadal periodicity that extended for about 100–150 years with great variation amplitude reaching of about 90%. Considering a possibility of solar activity signature in this variation we need to assume the existence of a phase change in correlation between rainfall level and solar activity. In this case a high correlation/anti-correlation coefficients with the 22-year solar cycle can be obtained: ≈0.8 for Fortaleza and 0.6–0.8 for Pelotas. No correlation was found for Campinas. Correlation with 24-year periodicity independent on solar cycle possibly connected with ocean–atmospheric coupling is ≈0.5 in Fortaleza for a total period of 151 years. Short term correlation of rainfall level with crossing a sector boundary of interplanetary magnetic field by Earth during ≈50 years of observations was also found. The results appear to have bearing both as a scientific instrument for progress in our understanding of sun–weather connections and, if established, possibilities for long term practical forecasting in the South American region and elsewhere.