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

Abstract

 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 at-mosphere general circulation model (AGCM) is further evaluated. The evaluation present-ed here is based on six recently proposed dynamics-oriented diagnostic metrics. Lag-longitude correlation maps of surface precipitation in the East Indian and West Pacific Oceans confirm the previously found improved representation of the MJO in the modi-fied ECHAM6.3 model compared to the standard configuration. In fact, the modified ECHAM6.3 outperforms the default ECHAM6.3 in five of the six MJO-related diagnos-tics evaluated here. In detail, the modified ECHAM6.3 (1) successfully models the east-ward propagation of boundary layer moisture convergence (BLMC); (2) captures the rearward tilted structure of equivalent potential temperature (EPT) in the lower tropo-sphere and forward tilted structure of EPT in the upper troposphere; (3) exhibits the rear-ward tilted structure of equatorial diabatic heating in the lower troposphere; (4) adequate-ly simulates the MJO-related horizontal circulation at 850 and 200 hPa as well as 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.