Simulations of linear responses to Madden-Julian oscillation heatings

The authors analyze the dynamics of wind and temperature perturbations associated with the Madden-Julian Oscillation (MJO) using a simple model and mathematical analyses. The objective of this work is to isolate the important dynamics of the coupling between convection and the large-scale circulation. A linear primitive equation model is used to simulate the MJO's structure as a linear response to a prescribed heating. The horizontal structure of the heating is based on satellite imagery, and the vertical structure (including amplitude and phase) comes from atmospheric budgets obtained from TOGA COARE. Experiments are carried out for both a basic state of rest and for basic states with empirical shear profiles. These simulations address the following questions: 1) can the observed MJO wind and temperature structure be modeled as a linear response to heating? 2) how are the circulations altered by nonzero basic state winds? 3) to what extent can the observed structure be represented with two vertical modes? These questions are motivated by the results of previous studies of the MJO and other convectively-coupled equatorial waves.