The coupled GCM ECHO-2. Part II: Indian ocean response to ENSO

The interannual variability of the Indian Ocean SST is investigated by anal yzing data from observations and an integration of a global coupled GCM (CG CM) ECHO-2. First, it is demonstrated that the CGCM is capable of producing realistic tropical climate variability. Second, it is shown that a conside rable part of the interannual variability in Indian Ocean SST can be descri bed as the response to interannual fluctuations over the Pacific related to ENSO. Although me Indian Ocean region also exhibits ENSO-independent inter annual variability, this paper focuses on the ENSO-induced component only. Large-scale SST anomalies of the same sign as those observed in the eastern equatorial Pacific Ocean during ENSO extremes develop in the entire tropic al and subtropical Indian Ocean with a time lag of about 4 months. This lea d-lag relationship is found in both the observations and the CGCM. Using th e CGCM output, it is shown that the ENSO signal is carried into the Indian Ocean mainly through anomalous surface heat fluxes.