Predictability of a Coupled Ocean–Atmosphere Model

Abstract

Abstract The predictability and variability of a coupled ocean-atmosphere model has been investigated by examining the growth of small initial perturbations during the evolution of the coupled system. The ocean model is first integrated in a forced mode for a duration of over 24 years beginning with January 1964 in which wind stress forcing for each month is prescribed from the observations. This provides surrogate analysis or control run with which predictions from the coupled model can be initiated and compared. Starting from January 1970 with each of the next 181 initial states from the control run, a prediction experiment was carried out for a duration of 36 months each using the fully coupled model. With this large ensemble of prediction experiments, a detailed analysis of growth of initial error and forecast errors was carried out. The SST forecasts are compared with observations as well as the control run. The root-mean-square difference between control and forecasts becomes larger than the standar...