Rainfall cycles with bidecadal periods in the Brazilian region

Abstract

Precipitation in Brazil for three meteorological stations (Pelotas: 31°45'S, 52°21'W: Campinas: 22°53'S, 47°04'W; Fortaleza: 3°45'S, 38°31'W) from 1849 up to 2000 were considered. Periodic analysis of annual rainfall in Pelotas and Fortaleza shows bidecadal periodicity over 100-150 years with variation amplitude of about 90%. High correlation/anticorrelation coefficients with the 22-year solar magnetic field cycle in Fortaleza are -77%±4% during 1849-1940 and +80.0±4% during 1952-2000, and in Pelotas 60%±13% in 1893-1920 and -84 %±4% during 1929-2000. Correlation with 24-year periodicity is +54%±6% in Fortaleza during 1849-2000. Short term correlations of Brazilian rainfall level with magnetic sector boundary of interplanetary magnetic field crossing by Earth, with solar flare particle events, and with Forbush decreases in cosmic rays during ∼ 50 years of observations were negative.