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Regional climate change over southern South America: evolution of mean climate and extreme events

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.

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Regional climate change over southern South America: evolution of mean climate and extreme events

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  1. Regional climate change over southern South America: evolution of meanclimate 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. Regional scenarios of climate change over southern South America 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

  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

  8. HadAM CRU MM5 Precipitation: Annual cycle

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

  10. MM5 HadAM Observations CRU

  11. Temperature: Annual cycle CRU MM5

  12. Regional simulation: Main biases • Model biases can be related to both deficiencies in the regional model configuration and deficiencies in the boundary conditions • The 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

  13. Regional scenarios: A2 – B2

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

  15. Changes in mean climate

  16. Changes in mean climate: Precipitation Present A2 B2

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

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

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

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

  21. Changes in mean climate

  22. Present A2 B2 Changes in mean climate: Temperature

  23. Present A2 B2

  24. 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.

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