Abstract
The simulated Madden-Julian oscillation (MJO) in the climate of the 20th Century (20C3M) experiment of 23 models participating in the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) is examined. The models having moisture-convergence-type convection schemes well simulate the MJO signal in precipitation. By analyzing the data from these models, we confirm that the MJO convection is active from the Indian Ocean to the western Pacific, consistent with the observations. However, analyses of the structure of the simulated MJO reveal that the convergence of the surface wind tends to be overestimated in the models. In addition, the peak of the MJO signal over the Indian Ocean is relatively weaker than that over the maritime continent and the western Pacific, and shifts westward in the models. These inconsistencies appear to arise from the distribution of sea-surface temperature (SST) bias. As a general tendency in all of the climate models studied, it is also demonstrated that the skill of the MJO simulation correlates positively with that of the climatological SST. Potential importance of the basic field and the air-sea coupling in the MJO simulation is suggested.
