Enhancement of MJO Variability in GFDL CM4 by Modulating SST Patterns

It has been well-known that coupling with the ocean in general circulation models (GCMs) improves the simulation skill of Madden-Julian Oscillation (MJO). This is the case in the latest version of GFDL model; the coupled-model (CM4) produces better MJO than the atmospheric model (AM4). We will show general diagnoses of AM4 and CM4, and demonstrate which fields are changed in CM4 compared to AM4, in favor of the existence of MJO.

Furthermore, we modulated the SST patterns in AM4 and found the MJO signals were enhanced. We will present a protocol to strengthen the MJO signals by modulating the SST, and discuss a potential reason why coupling with the ocean improves MJO simulations in the GFDL models.