ENSO influence on La Plata Basin precipitation in the HadGEM2-ES model.

Abstract

ENSO episodes affect South American precipitation and the frequency of extreme precipitation events, mainly in the La Plata Basin (LPB). We analyzed the representation of Central and Eastern ENSO diversity in a historical simulation of the HadGEM2-ES model, and the results showed that this model does not reflect the ENSO diversity. However, the model does represent the frequency of Eastern ENSO. Therefore, we used this model to analyze the influences of this type of ENSO on precipitation and frequency of extreme precipitation events over the LPB in simulations (historical scenario) and projections (RCP8.5 scenario), during austral summer and autumn. The HadGEM2-ES model reproduced the anomalous precipitation dipole pattern (increased precipitation over southeastern South America and decreased precipitation over the north/northeast) in eastern El Niño during both seasons, and the opposite pattern in eastern La Niña during the austral autumn. The model reproduced the patterns of anomalous frequency of extreme events that occur over South America during both seasons of eastern El Niño, but failed to reproduce these patterns during eastern La Niña. The future projections showed patterns of anomalous precipitation and frequency of extreme events that were similar to those simulated for the present, but were more intense and affected a wider area.