Factors for the improved performance in Madden-Julian Oscillation simulations

Abstract:

The simulation skill of the Madden-Julian Oscillation (MJO) has been examined using twenty-year climate simulation datasets from MJOTF/GASS global model comparison project. We investigate what factors distingush between highly performing model and poorly performing model. A moisture budget equation is examined and each term is calculated to find the most dominant processes. Time-mean moisture advection by MJO horizontal wind plays a role but moisture convergence by MJO zonal wind is assessed to strongly affect the simulation skill. The results suggest that intraseasonal zonal wind structure to the east of MJO convection needs to well represented to simulate the MJO realistically. The preconditioning factors and the role of suppressed convection are discussed.