Influence of the modes of climate variability in the Tropical Pacific and Atlantic on accumulated rainfall and reservoir water volumes in the Northeast Brazil

The volumes of artificial reservoirs as well as the accumulated rainfall over the Northeast region of Brazil (NEB) are sensible to the modes of climate variability. Thus, the objective of this study is to identify the relationship between the spatial patterns of the modes of climate variability in the Tropical Atlantic and Pacific Oceans, and the homogeneous rainfall subregions affecting the recharge of the water volumes of reservoirs in the NEB during the period from 1986 to 2018. For this end, we used monthly rainfall; monthly water volume data for artificial reservoirs; sea surface temperature anomalies in the Tropical Pacific and Tropical Atlantic Ocean. The first step was to apply cluster analysis to subdivide the NEB according to the monthly rainfall climatology. After, the technique of synthetic maximum rainfall series was applied. Then, the response time between rainfall climatology and reservoir water volume climatology was identified by means of cross‐correlation. Finally, the partial least squares regression was applied to infer the relationship between synthetic maximum rainfall series in each subregion and the modes of climate variability. Results showed that five homogeneous rainfall subregions with three distinct wet seasons. The synthetic time series of rainfall in the subregions were positively correlated with the climatology of the reservoir volumes with lags of up to 5 months after the beginning of the series. Both rainfall and the water volume of artificial reservoirs were sensible to the modes of climate variability of the studied oceans. The modes of climate variability that directly or remotely influence rainfall over the NEB subregions are important for seasonal forecasts during the wet season, they are important indicators of the occurrence of future dry periods. The restoration of reservoir volumes is slow‐paced and depends on a sequence of good quality average or above‐average wet seasons. However, a more in‐depth analysis of potential changes in the climatological patterns of precipitating systems over the NEB is needed.