Estudos de variabilidades interanual e interdecenal da precipitação pluvial das regiões hidrográficas da parte setentrional oriental do Brasil utilizando a análise de ondaletas.

Abstract

The general objective is to investigate the interannual and interdecadal variabilities of the rainfall time series of the Hydrographic Regions of the Northern-Eastern part of Brazil and to verify the phase relations of these variabilities between the precipitations of the Regions, as well as to correlate them with the anomaly indices of the sea surface temperature of the Atlantic and Pacific Oceans. The geographic area of study is located between 0.5º S to 20º S and 34.8º W to 55.4º W, covering the six Hydrographic Regions. We use precipitation data from 246 meteorological stations and pluviometric stations acquired from several Government Agencies of Brazil were used. In addition, we also use reanalysis data of 85 grid points (1º x 1º) from the Global Precipitation Climatology Center. We also used SST data from the Niño 3.4 region and the Tropical Atlantic gradient and the Pacific Decadal and Atlantic Multidecadal Oscillations from the Earth System Research Laboratory / National Oceanic and Atmospheric Administration. The analyses of the Continuous and Cross Wavelets Transforms and Wavelet Coherence and Fourier Harmonic were used. It was observed that the total annual rainfall of the Eastern Northeast Atlantic, Parnaíba, Western Northeast Atlantic, Tocantins-Araguaia, São Francisco and East Atlantic Hydrographic Regions present interannual variability with oscillations of 3 to 5 years, as well as interdecadal variabilities with oscillations from 11 to 13 years and 22 to 24 years, except those of the Western Northeast Atlantic Region that do not show oscillations with frequencies of 22 to 24 years. In the cross and coherence wavelets they are observed that the variability of the precipitations of the Hydrographic Regions (Eastern Northeast Atlantic, Parnaíba and Western Northeast Atlantic) and of the set of SST anomalies in the Equatorial Pacific, Tropical Atlantic gradient and PDO and AMO indices are in opposite phases. It can also be observed in the analyses of the cross wavelet transform and wavelet coherence that the variabilities with frequencies of 3 to 5 years, from 11 to 13 years and from 22 to 23 years of total annual precipitation of the Eastern Northeast Atlantic, Parnaíba and Western Northeast Atlantic Hydrographic Regions are in phases. While the phase of 3 to 5 year variability of Eastern Northeast Atlantic precipitation is lagged by 1/8 of the precipitation phase of the São Francisco and Tocantins-Araguaia and in phase with that of the Eastern Atlantic. On the other hand, the interdecadal variabilities with a frequency of 22 to 24 years of rainfall in the Eastern Northeast Atlantic Hydrographic Region are 1/8 out of phase in Tocantins Araguaia, one quarter of São Francisco and 7/8 of total annual rainfall of the East Atlantic Hydrographic Region. This shows that the dry and rainy periods in the 22-24 year scale in the Eastern Northeast Atlantic Region occur two to four years earlier than in the Tocantins-Araguaia and São Francisco and two to four years after the dry/rainy periods of the Eastern Atlantic. Therefore, it is possible to conclude that the events, ENSO, Atlantic SST Anomaly Gradient, ODP and OMA influence in the precipitations of the Hydrographic Regions of the Eastern Northeast, Parnaíba and Western Northeast Atlantic concomitantly, but differently for the Tocantins-Araguaia, San Francisco and the Eastern Atlantic.