Changes in temperature extremes for 21st century scenarios over South America derived from a multi-model ensemble of regional climate models

This study examines a set of 4 temperature extreme indices (cold and warm nighttime and daytime indices) from an ensemble of 4 regional climate models (RCMs) for present and future periods in South America (SA). These models were integrated in the framework of the CLARIS-LPB 7FP-EU-project. We analyze the capability of RCMs to reproduce such indices and explore changes projected by the models under the scenario A1B for the end of the 21st century. The work also analyzes the role of cloudiness, surface radiative forcing and meridional wind components on temperature extremes. Future projections show that, during the austral summer, the increase in the frequency of warm nights is larger than that projected for warm days. This result agrees with the projections for the seasonal mean fields of minimum temperature (TN) versus the maximum temperature (TX) over most of SA. The analysis for the La Plata Basin suggests that this behavior is consistent with the cooling effect of cloud cover affecting TX, while TN is affected by nighttime greenhouse warming. The relationship between cloudiness and TN and TX anomalies shows a nonlinear behavior for near full cloud cover conditions. Although TX and TN anomalies are sensitive to strong cold air advection, TX is more sensitive than TN. Thus, RCMs are useful tools to analyze both the spatial pattern of temperature extremes and the climatic factors involved.