Spectral Characteristics of the Annual Rainfall Series for Northeast Brazil

摘要

The rainfall series for Fortaleza (Ceara) 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 sigma a priori level. Amongst these, T = 12.9 and 25.1 years are significant at a 4 sigma a priori level, roughly equivalent to a 2 sigma a posteriori level. A Master Curve (for 1912 to 1978 only), obtained by averaging rainfall data for 93 stations having good correlations with Fortaleza, shows very prominent periodicitives at T = 5.6, 12.3 and 47.3 years, significant at a 3 sigma a priori level. T= 12.3 is significant at a 4 sigma a priori level. Predictions from both the Fortaleza series (1894 to 1976) and the Master Curve (1912 to 1978) indicated droughts during 1979 to 1983. This prediction seems to have come true. In the future, droughts during 1992 to 1994 and 2002 to 2006 are indicated.