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Open AccessArticle

Southern Hemisphere Sensitivity to ENSO Patterns and Intensities: Impacts over Subtropical South America

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Departamento de Física de la Tierra y Astrofísica, Universidad Complutense de Madrid, 28040 Madrid, Spain
2
Departamento de Ciencias de la Atmósfera, Universidad de la República, Montevideo 11400, Uruguay
*
Author to whom correspondence should be addressed.
Atmosphere 2020, 11(1), 77; https://doi.org/10.3390/atmos11010077
Received: 6 December 2019 / Revised: 25 December 2019 / Accepted: 26 December 2019 / Published: 9 January 2020
(This article belongs to the Special Issue Tropical Atlantic Variability)
El Niño flavors influence Subtropical South American (SSA) rainfall through the generation of one or two quasi-stationary Rossby waves. However, it is not yet clear whether the induced wave trains depend on the El Niño pattern and/or its intensity. To investigate this, we performed different sensitivity experiments using an Atmospheric General Circulation Model (AGCM) which was forced considering separately the Canonical and the El Niño Modoki patterns with sea surface temperature (SST) maximum anomalies of 1 and 3 °C. Experiments with 3 °C show that the Canonical El Niño induces two Rossby wave trains, a large one emanating from the western subtropical Pacific and a shorter one initiated over the central-eastern subtropical South Pacific. Only the shorter wave plays a role in generating negative outgoing longwave radiation (OLR) anomalies over SSA. On the other hand, 3 °C El Niño Modoki experiments show the generation of a large Rossby wave train that emanates from the subtropical western south Pacific and reaches South America (SA), promoting the development of negative OLR anomalies over SSA. Experiments with 1 °C show no impacts on OLR anomalies over SSA associated with El Niño Modoki. However, for the Canonical El Niño case there is a statistically significant reduction of the OLR anomalies over SSA related to the intensification of the upper level jet stream over the region. Finally, our model results suggest that SSA is more sensitive to the Canonical El Niño, although this result may be model dependent. View Full-Text
Keywords: El Niño flavors; extratropical teleconnections; rainfall over Subtropical South America El Niño flavors; extratropical teleconnections; rainfall over Subtropical South America
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Martín-Gómez, V.; Barreiro, M.; Mohino, E. Southern Hemisphere Sensitivity to ENSO Patterns and Intensities: Impacts over Subtropical South America. Atmosphere 2020, 11, 77.

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