Spectral characteristics of the annual rainfall series for Northeast Brazil

The rainfall series for Fortaleza (Ceará) is compared with similar series for several other locations in Northeast Brazil. It is shown that the correlations are high for distances up to about 600 km from Fortaleza. The Fortaleza series shows prominent periodicities at T = 2.1, 10.1, 12.9, 25.1, and 61.0 years, all significant at a 3 a priori level. Amongst these, T = 12.9 and 25.1 years are significant at a 4 a priori level. A master Curve (for 1912–1978 only), obtained by averaging rainfall data for 93 stations having good correlations with Fortaleza, shows very prominent periodicities at T = 5.6, 12.3 and 47.3 years, significant at a 3 a priori level. T = 12.3 is significant at a 4 a priori level. Predictions from both the Fortaleza series (1849–1976) and the Master Curve (1912–1978) indicated droughts during 1979–1983. This prediction seems to have come true. In the future, droughts during 1992–1994 and 2002–2006 are indicated.