Two leading modes of the interannual variability in South American surface air temperature during austral winter

The first two empirical orthogonal function (EOF) modes of the surface air temperature (SAT) interannual variability in the South American (SA) continent have been revealed in several previous studies. This presentation focuses on winter season and furtherly investigates the detailed advection and cloud-radiation processes and teleconnections from tropical sea surface temperature anomalies (SSTA) combining statistical analysis with Rossby wave dynamics and modelling experiments. The EOF1, featured with the anomalous center in the central part, is related to the tropical eastern Pacific SSTA, which may impact on the SA SAT variability through the Walker circulation and a regional Hadley cell. The anomalous center is largely attributed to low-level advection transported by the Hadley cell. The EOF2, as a fluctuation between anomalies in the southeast Brazil and the southern tip, is related to the SSTA surrounding the Maritime Continent, which may generate a barotropic wave train propagating to the SA continent. This wave train can strengthen high latitude westerly flow transporting warm advection to the southern tip, and generate southeast anomalous flow transporting cold advection to the southeast Brazil. Meanwhile, the cloud-radiation processes are also involved to enhance the advection-induced SAT anomalies in both areas.