The Impact of Assimilation of Altimeter Data on ENSO Hindcasts

The El Nino/Southern Oscillation phenomenon (ENSO) is the strongest interannual climate fluctuation. Its impact is felt worldwide. Prediction of this phenomenon is not only of scientific but also of public interest. ENSO prediction depends strongly on the accuracy of the ocean initial conditions. To improve the accuracy and investigate the impact on ENSO forecasts Topex/Poseidon altimeter data were assimilated into an Ocean General Circulation Model. For comparison, ocean model runs assimilating temperature data of the TAO/TRITON buoy array and ocean model runs assimilating Topex/Poseidon altimeter data together with SST data were performed as well. Ocean analysis were obtained with and without assimilation, and these ocean analysis were used as initial conditions for ENSO hindcast experiments with a hybrid coupled model (HCM). Differences between the ocean analysis and their impact on the ENSO hindcast skill are discussed.