Fluctuations in Annual Rainfall for Northeast Brazil1

Abstract

Fluctuations in annual rainfall totals for 229 stations in Northeast Brazil are analyzed by various statistical methods. Smoothed spectral density estimates are calculated for more than 140 stations using the Parzen lag window. Spectral peaks are observed to occur within the period ranges of 2-3 years, 3-5 years and 10-20 years. The regional distribution of the shorter period peaks is discussed. An analysis of trend is performed using the Mann-Kendall rank statistic and time series which are smoothed using a low pass Gaussian filter. Areal analyses of the percent of the 30-year normal rainfall (1931-1960) are used to illustrate the regional distribution and variability of precipitation.