PNNL

Abstract

The diurnal cycle of convection in the Maritime Continent (MC) has been hypothesized to act as a barrier to the eastward propagation of the Madden-Julian oscillation (MJO). To test this hypothesis, we use a regional model with realistic MJO to simulate an event from the boreal spring of 2013 that weakened and stalled over the MC. Two simulations are conducted: one that includes the diurnal cycle of insolation (CTL), and another without it (NO_DC). The MJO in the simulations was identified and tracked using a large-scale precipitation tracking (LPT) method that distinguishes propagation and non-propagation unlike the usual Real-time Multivariate MJO (RMM) method. In the NO_DC simulation, the absence of diurnal heating reduces land precipitation, allowing more continuous eastward MJO propagation. An analysis of moist static energy (MSE) budget reveals that MJO maintenance in NO_DC is due to increased longwave heating and reduced advection, whereas the persistent MJO propagation in NO_DC is due to increased advection and reduced longwave heating and surface latent heat flux. These processes, however, may vary across different parts of the MC, emphasizing the complexity of MJO propagation across the MC..