Role of cloud radiative feedback in the Madden–Julian oscillation dynamics: a trio-interaction model analysis

Abstract

The authors expand the original wave dynamic-moisture (WM) model by implementing the cloud radiative feedback (CRF) to study the role of the CRF in the Madden–Julian oscillation (MJO) in comparison with the role of the planetary boundary layer (PBL) process. The linear instability analysis is used to elucidate the reactions of the WM mode, WM-CRF mode, WM-PBL mode, and WM-PBL-CRF mode. Compared with the stationary and damped WM mode, the CRF can present an important instability source for all wavenumbers without the planetary-scale selection and tends to slow down the planetary-scale eastward propagation. On the other hand, the PBL process, with the planetary-scale selection, can destabilize the eastward propagation while accelerate the eastward propagation of the planetary-scale oscillation. When the PBL and the CRF processes are both included, the unstable mode is achieved and period is nearly 20–90 days, consistent with the observations. Both the WM and the WM-CRF modes present unrealistic coupled Kelvin–Rossby wave structure, which disagrees with the observations. These caveats can be remitted in the WM-PBL mode and the WM-PBL-CRF mode. The PBL can couple the Kelvin and Rossby waves and present the observed geopotential low in front of the convective center. The CRF, however, can make the phase relation between the precipitation anomalies and pressure anomalies changed in the presence of PBL process.