Observational evidence for the southern hemisphere teleconnection patterns in austral winter are examined through upper and lower-level circulation, using NCEP reanalysis for the period June-August 1979-95. Rossby wave activity into southern and southeastern Brazil, as well as Amazonia, from the midlatitudes. The occurrence of cold outbreaks and freezes in subtropical and even tropical Brazil, are linked to circulation features in both tropics and extra tropics that resemble wave trains originated somewhere on the western Pacific, and that propagate all the way across to the Pacific towards South America. This variability is coupled to large-scale changes in the temperature fields South America south of the equator, and to convection in northern South America. This teleconnection represent a wave like result of local anomalies in the atmospheric circulation over the western Pacific and their influence on the temperature conditions in the remote areas of southern and southeastern Brazil.
In this study we examine the observed atmospheric circulation, air temperature and convection anomalies that leads to strong surface cooling in southern Brazil during austral wintertime (JJA), on time scales of less than a month. This is an attempt to identify and isolate the forcing of the wave train and to study their propagation throughout the Pacific Ocean before, during, and after freeze events episodes in southern Brazil, and allowing a forecasts of these events. We expect to prove that the cold outbreaks due to incursions of polar air into tropical and subtropical Brazil, and the day-to-day variations of surface air temperature on those regions may be driven by wave activity originating in the western Pacific, that travel across the Pacific, and once reaching the west coast of South America are directed toward the equator to the east of the Andes.