MJO-ENSO teleconections during the boreal winter in projections of future climate in the IPCC AR4 Simulations

Effect of the global warming on the Madden-Julian Oscillation (MJO) and the impact on convective activity and circulation in the subtropics to midlatitudes in the boreal winter are statistically investigated. The projected change of the MJO-teleconnection in the East Asia region in the El Nino/Southern Oscillation (ENSO) is also examined. The analyses are performed using the historical (20C3M) and the scenario (A1B) runs in the coupled ocean-atmosphere climate models in the Coupled Model Inter-comparison Project 3 (CMIP3) for the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4). In the 20C3M experiment, the lag-regression analysis show that the active and suppressed convections associated with the MJO in the models that exhibit lower mean sea surface temperature (SST) bias than that of observation do not propagate to the eastern of 160°E. However, it is found that the convections with the MJO in future climate propagate cross the date line due to the SST warming in the tropical Pacific. The analyses in the 20C3M experiment show that common feature in four successful models (Best models) over both tropical and East Asia regions use the moisture convergence parameterization scheme, while three models (Mid-poor) only in the tropics use relaxed adjustment schemes or prognostic closure schemes. In the Mid-poor models, no precipitations with the MJO appear in the East Asia due to little southerly moisture transport from the tropics indicating very weak coupling of the circulations between tropics and extra tropics. In future climate, no significant increased precipitation with MJO occurs in the East Asia despite increased moisture transport. These results suggest that the moisture convergence parameterization scheme is more effective to the realistic producing of the precipitation in the subtropics to midlatitudes rather than the reproducibility of mean SST. Composite analyses of Best models in different ENSO phase indicate that the pattern of MJO-midlatitude teleconnections change in the future climate, although it appears no significant change of the total convection teleconnected with MJO in the East Asia. Convections teleconnected with MJO for ENSO warm phase over the East Asia largely contribute to the total convection than that for ENSO cold phase in the observation and Best models. In the future climate, it is found that the convection response to ENSO cold phase tend to increase. It is suggested that this increase is associated with the effective change of moisture transport from tropical Indian Ocean via Southeast Asia to the midlatitude East Asia region