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GEOPHYSICAL RESEARCH LETTERS, VOL. 30, NO. 21, 2115, doi:10.1029/2003GL018277, 2003

Antarctic Oscillation signal on precipitation anomalies over southeastern South America

Gabriel E. Silvestri

Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina


Carolina S. Vera

Centro de Investigaciones del Mar y la Atmósfera (CIMA-CONICET) and Departamento de Ciencias de la Atmósfera y los Océanos, Universidad de Buenos Aires, Argentina


Abstract

The relation between the Antarctic Oscillation (AAO) and the precipitation in southeastern South America (SESA) is examined. The AAO influence is particularly strong during winter and late spring although of opposite sign. In particular during spring, AAO positive (negative) phases are associated with the intensification of an upper-level anticyclonic (cyclonic) anomaly, weakened (enhanced) moisture convergence and decreased (increased) precipitation over SESA. The combined influence of both ENSO and AAO on SESA precipitation was also explored and significant correlation values between both oscillations are only observed during spring. Results show that during that particular season, AAO activity produces a strong modulation of the ENSO signal on SESA precipitation.

Received 29 July 2003; accepted 15 October 2003; published 12 November 2003.

Index Terms: 1620 Global Change: Climate dynamics (3309); 3309 Meteorology and Atmospheric Dynamics: Climatology (1620); 3319 Meteorology and Atmospheric Dynamics: General circulation.

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Citation: Silvestri, G. E., and C. S. Vera (2003), Antarctic Oscillation signal on precipitation anomalies over southeastern South America, Geophys. Res. Lett., 30(21), 2115, doi:10.1029/2003GL018277.