On the relationship between Pacific meridional mode and ENSO in a coupled GCM

The Pacific Meridional Mode (MM) is regarded as a notable off-equatorial phenomenon, of which features are anomalous north-south sea surface temperature gradient and anomalous southwesterly wind near the inter-tropical convergence zone during boreal spring. Recently, possible linkage between MM and ENSO has been raised but the detailed mechanisms are not fully investigated yet. Here, using a long-term coupled general circulation model (CGCM) simulation, we investigate how MM is related to the development of ENSO. Results show that some ENSO events are accompanied by MM in developing phase and have coterminous SST anomaly patterns of MM, while some are not. Reasons for such selective triggering mechanism of MM are addressed in this study.