Extended Abstract (124K)P1.19
Teleconection between tropical west pacific convection and cold surges in the southern South America
Gabriela V. Müller, Centro de Investigaciones del Mar y la Atmosfera, Buenos Aires, Argentina; and T. Ambrizzi, M. N. Nuñez, and S. Ferraz
A multilevel primitive equation model is used to examine a possible teleconection between the convection in the tropical west Pacific and freezing events in the region called “Pampa Húmeda” in the center-east Argentina during austral winter. The sensitivity of the phase and amplitude of the quasi-stationary Rossby wave response to the heating anomaly over the tropical West Pacific ocean is examined through numerical simulations. Indeed, the model results indicate that the position of the heating source on the western Pacific (~120°E) is important to generate wave propagation patterns, which have a good resemblance to those obtained in the observational analysis and recent studies found in the literature.
From the observational studies it was found that in the years with above average freezing events over the Pampa Húmeda, there is a convergence pattern of the subtropical and subpolar jets in this region. Therefore, synoptic systems are conducted through the continent, with cold air advection from the south-southwest direction. On the other hand, when there is below average cold surges over the center-east Argentina, the subtropical and subpolar jets show a divergent pattern, with seems unfavorable for synoptic systems penetration. Thinking in terms of the wave theory and from the comparison of the observational and numerical results it is suggested that freezing events may occur when the subtropical and subpolar waveguides are in the right phase, which allow the incursion of large amplitude troughs from the south part of South America.
Poster Session 1, Poster Session
Monday, 24 March 2003, 3:00 PM-3:00 PM
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