Fundamental Causes of Propagating and Nonpropagating MJOs in MJOTF/GASS Models

• DOI: 10.1175/jcli-d-16-0765.1
• Publication Date: 2017-02-16T18:47:39Z
• Authors: Lu Wang; Tim Li; Eric Maloney; Bin Wang
• Keywords: Madden–Julian oscillation; Diabatic; Anomaly (physics); Parametrization (atmospheric modeling); Atmospheric models

Abstract This study investigates the fundamental causes of differences in Madden–Julian oscillation (MJO) eastward propagation among models that participated a recent model intercomparison project. These are categorized into good and poor groups characterized by prominent nonpropagation, respectively. Column-integrated moist static energy (MSE) budgets diagnosed for models. It is found zonal asymmetry MSE tendency, characteristic MJO propagation, occurs group, whereas such an does not exist group. The difference arises mainly from anomalous vertical horizontal advection. former attributed to upper-midtropospheric velocity anomalies acting on background gradient; latter asymmetric distribution low-tropospheric meridional wind advecting moisture fields. Based diagnosis above, new mechanism emphasizes second-baroclinic-mode proposed. A set atmospheric general circulation experiments with prescribed diabatic heating profiles was conducted investigate different circulations between numerical reveal presence stratiform at rear convection responsible anomaly important strengthening lower-tropospheric poleward flows east convection. Thus, key improving correctly reproduce heating. roles Rossby Kelvin wave components particularly discussed.