Southern Hemisphere teleconnections in a climate simulation using the CPTEC/COLA GCM

Teleconnection patterns in the Southern Hemisphere have been identified in many observational studies and in a few numerical model results. Wavetrain patterns related to the Rossby wave propagation manifest in different frequency bands. High frequency anomalous patterns are associated with synoptic systems such as cold fronts moving from the Pacific Ocean to the Atlantic Ocean, crossing South America. Some low frequency patterns are associated with tropical convection and show wavetrain structure extending from the tropics to higher latitudes. The objective of this study is to identify high and low frequency anomalous patterns in a numerical model simulation of 11 years using the CPTEC/COLA GCM. Observed monthly SST from 1986 to 1996 are applied as the boundary condition in the model with T42L28 resolution. Empirical Orthogonal Function analyses of the daily 200 hPa meridional wind component are performed for the austral winter and summer seasons included in the period from 1990 to 1994. Analyses are done for two regions (one in the global zone between 70S and 30S and another in the western hemisphere between the equator and 70S) to allow comparisons of the model patterns with those obtained in a previous study for the NCEP/NCAR reanalysis data For the hemispheric region and considering the high frequency band, the model reproduces a wavetrain pattern similar to that noted in the reanalyzed data, which has been shown to be associated with the displacement of synoptic systems in the middle latitudes. Similarly, the western hemisphere analysis for the high frequency data reveals a wavetrain pattern extending from the South Pacific to the Atlantic Ocean and crossing the South America with the anomalous centers tilting in the northwest -southeast direction, as noted for the observed data analyses. The dominant austral patterns show features associated with cold air outbreaks over South America. The results show the skill of the climate model in a long-run simulation in reproducing the observed transient patterns. Simulated low frequency patterns are also analyzed and compared with the observational patterns.