Mechanics of the Madden Julian Oscillation in a Cloud-Resolving Model with Parameterized Beta-Plane Dynamics

Convection and the beta-plane dynamic modes are key ingredients of the Madden Julian Oscillation (MJO). How they work together making planetary scale MJO are not well understood. We develop an idealized modeling framework to address this issue. Our approach starts from quasi two-dimensional cloud-resolving model (CRM) with its length equivalent to the earth’s circumference. Two gravest beta plane modes, the n=0 (Kelvin) and n=1 (Rossby) modes driven by the diabatic heating, are incorporated in a CRM. Zonal and meridional advection by these dynamic modes are either explicitly or implicitly included in the model. A set of numerical experiments initialized from the radiative-convective equilibrium with or without the Walker circulation are carried out. New diabatic modes distinct from the either Kelvin or Rossby waves are found in these experiments. We will discuss the structure and propagation of these new modes and their relevance to the MJO in nature.