A crucial role of land-atmosphere interactions in shaping subseasonal convective variability over the Maritime Continent in idealized model simulations

Abstract

The limitations of current Earth system models in accurately representing the propagation of the Madden-Julian Oscillation (MJO) over the Maritime Continent (MC) significantly hinder our ability to make skillful subseasonal-to-seasonal predictions of extreme weather events worldwide. Additionally, our understanding of the intricate interactions between the MJO and the MC remains incomplete. Focusing specifically on Sumatra Island, this study investigates the key processes underlying the damping effect of MC islands on the eastward-propagating MJO based on a series of idealized atmospheric-only global model simulations, which include realistic land-sea distributions and topography of the MC within an aqua-planet environment. The findings suggest that the coupling between land and atmosphere, driven by interactions among clouds, radiation, land surface temperature, and convective instability, plays a critical role in reducing MJO convection over the MC. Notably, incorporating the diurnal cycle of convection in the model significantly enhances this damping effect, due to more active interactions between convection and radiation, consistent with previous modeling studies.