Sensitivity of LMD general circulation model in South America to a SST change in tropical pacific

A medium resolution version (72x45x19) of the LMD (Laboratoire de Meteorologie Dynamique du CNRS) atmospheric general circulation model is applied in order to obtain a climate response in a stretched grid domain over South East Brazil in response to a La Niña signal. The first part of this work consists of evaluating the impact of increasing locally model resolution through the introduction of a zoom centered at Rio de Janeiro. Near the center of the zoom, the resolution is increased roughly by a factor of 2. For both regular grid and stretched grid, two simulations of 4 years have been realized. The comparison between the two simulations reveals that some characteristics are improved in the zoom simulation, but the systematic errors, probably due to inadequate physical parameterizations, persist whatever the resolution of the model. The second part of this work is to study the model's sensitivity to changes of SST (Sea Surface Temperature). An artificial cooling is introduced in eastern tropical Pacific in order to simulate a La Niña event. Results for summer season are presented.