L. Zamboni, A. Cherchi, M. Barreiro, F. Kurcharski, "Dynamic of the Impact of ENSO Flavors on Precipitation over La Plata Basin," Preprint ANL/MCS-P2009-0112, January 2012. [pdf]
In this study we use observational datasets and two atmospheric general circulation models to demonstrate that the mechanism linking the canonical El Nino Southern Oscillation (ENSO) to precipitation anomalies in La Plata Basin (LPB) during the austral Spring is found even when Sea Surface Temperature anomalies (SSTa) are largest over the central Pacific (Dateline El Nino). Corresponding to both flavors, increased (decreased) precipitation is observed during El Nino (La Nina) in LPB, while opposite anomalies occur to the northeast of South America (SA). In contrast, positive loads shift to the north when SSTa are uniform from the eastern to the central Pacific in what forms the additional flavor (Spread) we document here. Besides the dynamical features already reported in the literature for the impact of ENSO in LPB, we found evidence of an additional wave train emanated from the tropical Pacific meridionally toward the southern hemisphere in our modeling experiments. This wave can be a standalone pattern but also interfere and amplify the Pacific-South American Mode over the eastern Pacific and SA. Additionally, we provide evidence of a Gill type of response to the east of the heating region and whose effects are appreciated on the local circulation over SA and thus precipitation over LPB.