Seasonal Forecasting at ECMWF : predicting ENSO
J. O. S. Alves, D. L. T. Anderson, M. A. Balmaseda, J. Segschneider and T. N. Stockdale
Seasonal Forecasting Group, ECMWF
Errors in the forecasts can arise from uncertainties in the atmosphere model, ocean model and initial conditions (ocean, atmosphere, Iand). Some difficiencies in the coupled model forecasts of equatorial Pacific SSTs over the 90s are dicussed. Errors in the forecasts due to uncertainties in the ocean intial conditions are examined using coupled forecasts starting from different initilisation methods (with and without ocean data assimilation and different assimilation set ups). Results show that ocean data assimilation can have a large positive impact on the coupled model forecasts of ENSO. Links are found between these forecasts and uncertainties in the ocean initial state in the central and western equatorial Pacific, as well as the north western tropical Pacific, outside the TOGA-TAO array region. The lack of salinity observations means that errors in the salinity field cannot be corrected. Assimilating temperature but not salinity can lead to dynamical imbalances along the equator.
