Descripción: We investigate the performance of one stretched-grid atmospheric global model, five different regional climate models and a statistical downscaling technique in simulating 3 months (January 1971, November 1986, July 1996) characterized by anomalous climate conditions in the southern La Plata Basin. Models were driven by reanalysis (ERA-40). The analysis has emphasized on the simulation of the precipitation over land and has provided a quantification of the biases of and scatter between the different regional simulations. Most but not all dynamical models underpredict precipitation amounts in south eastern South America during the three periods. Results suggest that models have regime dependence, performing better for some conditions than others. The models' ensemble and the statistical technique succeed in reproducing the overall observed frequency of daily precipitation for all periods. But most models tend to underestimate the frequency of dry days and overestimate the amount of light rainfall days. The number of events with strong or heavy precipitation tends to be under simulated by the models. © The Author(s) 2009.

Descripción: The objective of this research is to study the main variability modes of the frequency of extreme temperatures in the south of South Amenica, their relation to sea surface temperatures (SSTs), and some indices of atmospheric circulation in the Southern Hemisphere. Observational data and reanalysis data were used for this purpose over the 1964-2003 period. An initial analysis showed that between the months of March and June, the frequency of wann events (especially warm nights) is highly associated with the SST in coastal zones. A wavelet analysis showed that the main variability mode found at a seasonal scale was an 8-year wave signal present in spning that remains active until the 1990s; it was noticeable in the analysis of cold nights, Atlantic SSTs, Pacific SSTs, and the Southern Annular Mode (SAM). A cross-wavelet analysis among them reflected this signal as a common variability mode, with the positive phase of the SAM congruent with the warmest conditions in the coastal zones of the Atlantic Ocean and lower cases with cold nights at the reference meteorological stations analyzed. Although longer series are desirable for low-frequency variability analysis, the results agree with previous studies that take into account an 8-year periodicity of the baroclinic waves at the Southern Hemisphere, supporting the relevance of the 8-year signal. Copyright 2008 by the American Geophysical Union.