Inter-annual variability of precipitation in the tropical Western Pacific (WP) has been know as one of the key issues for the seasonal prediction over East Asia both during its winter (DJF) and summer (JJA). The MRI/JMA AGCM (Shibata et al., 1999) integration with the observed SST successfully simulates the variability of the tropical Western Pacific precipitation for both DJF and JJA.

The relationship between the tropical Western Pacific precipitation and the local SST variability is different for DJF and JJA. High correlation is clear for DJF, but almost no correlation for JJA. The tropical Western Pacific precipitation for JJA tends to be related with the El Nino SST for the previous DJF. The JJA SSTs over the Indian Ocean and the central Pacific off the equator keep the memory of the previous DJF El Nino3.4 SST to some extent. The JJA precipitation over the above two regions may play a role to create the JJA precipitation over the Western Pacific related with the El Nino SST for the previous DJF.

The simulated precipitation over the eastern Indian Ocean for DJF is positively related to the local SST anomaly. The observed relationship is opposite. Generally, the inter-annual variability of precipitation in the AGCM tends to be positively related to the local SST variability at each oceanic region on the whole. On the other hand, that local relationship in the observation differs from region to region.