1. Regional climate change over southern South America: evolution of mean climate and extreme events Silvina A. Solman CIMA (CONICET-UBA) Buenos Aires ARGENTINA 1st Ibero-American Workshop on Climate Dynamics, Climate Change and Regional Climate Modeling, Sao Paulo, Brasil 20-23 August 2007

2. Why a regional simulation is needed over southern South America?

3. Why a Regional Model is needed over southern South America?

4. Goals To assess the capability of the regional model to simulate present-day regional climate over southern South America To identify systematic model errors To determine the added value of using a regional model To derive the regional climate change pattern mean climatic conditions seasonal cycles extreme events A series of regional climate simulations performed with the MM5 (Fith-generation Pennsylvania State University-NCAR /Penn State- NCAR) regional model nested within time-slice global atmospheric model experiments conducted by the HadAM3H (Hadley Centre). model for different periods: –1981-1990 Present climate –2081-2090 SRES A2 –2081-2090 SRES B2 Regional scenarios of climate change over southern South America

5. Present climate simulation Low-low level circulation patterns –SLP, 850 hPa winds Surface variables –Precipitation –Mean, Maximum and Minimum temperatures

6. Solman et al, 2007 Clim Dyn)

7. 850 hPa wind (1981-1990) HadAM3H NCEP MM5  westerlies  LLJ

9. Precipitation: Annual cycle HadAM CRU MM5

10. Extreme events: Precipitation 95th percentile Wet day freq MM5 HadAM Observations CRU

11. MM5 HadAM Observations CRU

13. Temperature: Annual cycle CRU MM5

15. Regional simulation: Main biases Model biases can be related to both deficiencies in the regional model configuration and deficiencies in the boundary conditions T he location and intensity of the Chaco Low (topographically- induced systems) is not well simulated affecting the moisture advection over La Plata basin and, in consequence, rainfall is underestimated over the region West of the Andes overestimation of rainfall is related mainly to biases in the boundary conditions, which tend to produce too strong westerlies, and, in consequence, enhanced synoptic scale variability over the Pacific storm-track Biases in mean and maximum temperatures are consistent with biases in precipitation: negative (positive) biases are found over regions where rainfall is overestimated (underestimated) The regional model improves the simulation of extreme events compared with the global model

16. Regional scenarios: A2 – B2

17. Regional scenarios: Changes in mean climate SLP Nuñez et al. (2007)

18. Changes in mean climate

19. Present A2 B2 Changes in mean climate: Precipitation

20. Changes in extreme events: Precipitation Present climate A2 B2

21. Changes in extreme events: Precipitation Present climate A2 B2

22. Changes in extreme events: Precipitation Present climate A2 B2

23. Changes in extreme events: Precipitation Present climate A2 B2

24. Changes in mean climate

25. Present A2 B2 Changes in mean climate: Temperature

26. Present A2 B2

27. Final remarks: Regional scenarios of climate change A southward extension of the summer mean Atlantic and Pacific subtropical highs Stronger westerlies, mainly during JJA A general increase in precipitation in northern and central Argentina especially in summer and fall Increasing precipitation is mainly due to more intense extreme events rather than more rainy days A general decrease in precipitation in winter and spring mainly due to less rainy days Large increase in precipitation over the southern Andes during winter and increase in extreme events Large decrease in precipitation over subtropical andes during winter and decrease in the frequency of wet days In the two scenario runs the warming in southern Brazil, Paraguay, Bolivia and northeastern Argentina are larger in winter Over southern regions the warming is weaker Minimum temperatures rise is larger than maximum temperatures rise.