Assessing teleconnections among ENSO, the tropical Atlantic and precipitation anomalies, and their effects on a tropical watershed

Large-scale ocean-atmosphere mechanisms in distant regions can affect regional variability in diurnal convection through teleconnections and their feedback. This ocean-atmosphere interaction and its impacts on extreme events are well documented at a large scale but need to be better studied in regions where biomes intersect, such as is the case in the Mearim River Basin (MRB). The ocean-atmosphere interaction was investigated through sea surface temperature (SST) anomalies for ENSO regions (Niño 1 + 2; Niño 3; Niño 3.4 and Niño 4) in the tropical Pacific. In the Atlantic, SST was analyzed for the Tropical North Atlantic (TNA) and Tropical South Atlantic (TSA) regions. The rainfall anomaly index (RAI) was calculated for the entire MRB using the daily data from the Daily Gridded Meteorological Variables in Brazil (gridBR) dataset, with a spatial resolution of 0.25° × 0.25° over the 1983–2013 period. The cross-correlation function (p value < 0.05) with a lag of 0–12 months was applied to the RAI and SST. Our results indicate that the RAI values have a significant correlation with the TNA, being responsible for 60% of the wet events in the MRB during the Southern Hemisphere summer. In the Pacific, on the other hand, none of the ENOS anomaly indices showed significant (moderate or strong) correlations with the temporal and spatial patterns of RAI for the MRB. These results may assist public and private managers in managing water resources more efficiently for monitoring and predicting extreme events.