Revisiting the Impact of Stochastic Multicloud Model on the MJO Using Low-Resolution ECHAM6.3 Atmosphere Model

Based on the preceding work, the influence of the stochastic multicloud model (SMCM) on the Madden–Julian oscillation (MJO) in the state-of-the-art ECHAM6.3 atmospheric general circulation model (AGCM) is further evaluated. The evaluation presented here is based on six recently proposed dynamics-oriented diagnostic metrics. Lag–longitude correlation maps of surface precipitation in the eastern Indian Ocean and West Pacific Ocean confirm the previously discovered improved representation of the MJO in the modified ECHAM6.3 model compared with the standard configuration. In fact, the modified ECHAM6.3 outperforms the default ECHAM6.3 in five of the six MJO-related diagnostics evaluated here. In detail, the modified ECHAM6.3 (1) successfully models the eastward propagation of boundary layer moisture convergence (BLMC); (2) captures the rearward-tilted structure of equivalent potential temperature (EPT) in the lower troposphere and forward-tilted structure of EPT in the upper troposphere; (3) exhibits the rearward-tilted structure of equatorial diabatic heating in the lower troposphere; (4) adequately simulates the MJO-related horizontal circulation at 850 and 200 hPa and the 300 hPa diabatic heating structure. These evaluations confirm the crucial role of convective-parameterization formulation on GCM-simulated MJO dynamics and support the further application and exploration of the SMCM concept in full-complexity GCMs.