Empirical singular vector method for ensemble El Nino-Southern Oscillation prediction with a coupled general circulation model

Abstract

Optimal initial perturbation is an important issue related to the improvement of the current seasonal climate prediction. In this study, we have applied the empirical singular vector method to ensemble El Nino-Southern Oscillation (ENSO) prediction with the Seoul National University coupled general circulation model. It is found that from the empirical linear operator, the leading singular mode, which represents the fast growing error mode in the tropical Pacific, shows El Nino-like perturbation in the present coupled model. When the singular vector is used as an initial perturbation, the forecast skill of ENSO is significantly improved. Further, it is demonstrated that the predictions with the singular vector have a more reliable ensemble spread, suggesting a potential merit for a probabilistic forecast.