Figure 1. Predictive skills for 2–5 years lead time.

Potential predictive skills of (a–c) SLP, (d–f) SST and (g–i) SSH anomalies for averaged 2–5 years lead time in the initialized run (left), the uninitialized run (center) and their difference (right). Predictive skills in the initialized hindcast and uninitialized runs are measured per grid-point by the anomaly correlation coefficient and with the same number of initial cases (that is, 10 cases) by comparing with the assimilation run that is comparable to the observation. Correlation coefficients of 0.44, 0.55, 0.72 and 0.85 correspond to the statistical significance at 90, 95, 99 and 99.9% levels with eight degrees of freedom on the basis of one-side Student's t-test. Dotted areas indicate the statistically significant (>90%) difference in the anomaly correlation skill between the initialized and the uninitialized runs, as measured by Fishers z-score.