Wavelet analysis was applied to the standardized rainfall time series in the south-eastern in the Democratic Republic of the Congo in order to determine periods of rainfall fluctuations in this region at interannual and decennial timescales and to assess the influence of regional or remote climate phenomena on the rainfall of that sector between 1940 and 1997. The local, the global and the scale-averaged wavelet power spectrum of the rainfall time series of that sector indicate an important fluctuation between practically 1960 and 1970. Wavelet coherence spectral analysis shows that the southern oscillation El Nino phenomenon, the Western Hemisphere Warm Pool, the Atlantic Ocean climate variability and the Indian Ocean dipole have a very weak influence on rainfall on this territory. Scale-averaged wavelet coherence in 2-16 years band is lower than 0.5 whatever the climate index considered. Other factors must also be considered in the study of rainfall variability in this study area.

The singular spectral analysis, the multitaper method and the wavelet analysis were applied to the standardized average series of the temperatures in the oriental mountainous zone in the Democratic Republic of the Congo in order to determine the periods of temperature fluctuations at interannual and decennial timescales in that region. These different spectral methods reveal in the temperatures of this region a signal of four years period close. The spectral analysis by wavelet coherence was also applied to the couple made of temperature series and each principal characteristic indice of Atlantic, Indian and Pacific basins in order to assess the influence of these basins on temperatures over that region . This analysis shows that the phenomenon El Ninõ Southern Oscillation phenomenon and the Western Hemisphere Warm Pool are the principal drivers of the temperature fluctuations in this area on the interannual scale of 2-8 years, the coherence’s peak between the temperatures and these phenomena is located at approximately four years. The anomalies of sea surface temperatures of the tropical Atlantic Ocean also contribute to the fluctuations of the temperatures in this area on a scale 2-4 years by the means of the Atlantic Multidecennial Oscillation, the variability of the Tropical Northern Atlantic and the Atlantic Meridional Mode. The contributions of the oscillation of the North Atlantic, the variability of the Tropical Southern Atlantic and the Dipolar Mode of the Indian Ocean to the fluctuations, on interannual and decennial timescales, of the temperatures on this mountainous region are not significant.