Representation of precipitation and moisture transport in Southern South America in the WCRP CMIP3 Multi-Model dataset.

CARLA GULIZIA; INÉS CAMILLONI; MOIRA DOYLE

Melbourne, Australia

Congreso; 9th International Conference on Southern Hemisphere Meteorology and Oceanography; 2009

Climate change is nowadays considered as one of the greatest problems humanity is facing due to the magnitude of its impact on economy, society and ecology. Southern South America, and in particular La Plata Basin, are areas where climate change is detected with major intensity. The principal objective of this study is to evaluate the ability of GCMs available from the WCRP CMIP3 Multi-Model Dataset Archive to represent the present climate (1960-1999) of southeastern South America with emphasis on precipitation and relevant atmospheric processes such as water vapor transport. Seasonal precipitation fields derived from GCMs were compared with the University of Delaware database available in a 0.5º x 0.5º grid. The evaluation of present climate model simulations was done using Climate of the 20th Century (20C3M) experiments. GCMs skill to represent the observed precipitation and water vapor transport fields was assessed from the linear spatial correlation coefficients between seasonal mean fields derived from the observed database and from GCMs. Differences between observed and GCM annual mean fields were also calculated to identify regions with large biases. Precipitation analysis shows that the lowest linear spatial correlation coefficients are observed during the austral autmn and spring months. All GCMs show some similar patterns: underestimation of annual rainfall over the La Plata Basin and central Chile and overestimation over the central-western of Argentina, northern Chile, Bolivia and to the south of 40ºS. Results also show some deficencies of the GCMs to represent the regional moisture transport explaining the precipitation underestimation over La Plata Basin.