Impact of sea-surface temperature anomalies in the equatorial Indian Ocean and western Pacific on the Asian summer monsoon in three general circulation models

The sensitivities of the Asian summer monsoon to sea-surface temperature (SST) anomalies in the equatorial Indian Ocean and the western Pacific are compared in three different general circulation models (ARPEGE, ECHAM, UGAMP). The impacts to idealized anomalies of 1 K show common features, notably a weaker monsoon for warm equatorial Indian Ocean SSTs. For a warm western Pacific, the impact over India shows a dipole structure with increases in the southern part and decreases in the northern part for the ECHAM and UGAMP models, with ARPEGE showing a different response. The models also disagree on the linearity of the impact. The response to cold anomalies is nearly the same, with opposite sign, as for warm anomalies in the ECHAM model but is non-linear in the ARPEGE and UGAMP models. The study underlines the need for accurate measurements of the regional SSTs, which are as equally important for local rainfall as the remote large-scale impact from the El Nino-Southern Ocean oscillation. Copyright (C) 2004 Royal Meteorological Society.