Seasonal predictability in winter over eastern Asia using the JMA global model

To study seasonal predictability over the eastern Asia region, we carried o ut seasonal simulation experiments with a T63L30 Atmospheric General Circul ation Model developed at the Japan Meteorological Agency. Integrations over 120 days for four cases of 5-member ensembles were carried out with the us e of the observed sea surface temperature (SST). It was found that simulated scores of ensemble-mean forecast 500 hPa height calculated over eastern Asia in boreal winter, at least during El Nino eve nts, were more skilful than those over the whole northern hemisphere. Observations show that the Western Pacific (WP) pattern, which is one of lo w-frequency modes, has some statistical correlation with SST anomalies over the eastern equatorial Pacific. The model used in this experiment has an a bility to reproduce the WP pattern with reasonable intensity. This may be o ne of the reasons for the high skill demonstrated over the eastern Asia reg ion in boreal winter.