Low-level heating and the MJO

Poster PDF

Description

This poster will present results from model runs of a modified version of CAM4 to show the relative importance of low-level heating in the initiation and evolution of the Madden-Julian Oscillation (MJO). While eastward propagating tilted heating associated with a cloud population that evolves from shallow to congestus to deep convection forces the most realistic MJO signal in OLR and low-level and upper level winds, an eastward propagating low-level heating with no tilt also forces a realistic MJO response. Perhaps most interesting is that a very weak low-level heating over the entire Indian Ocean and West Pacific that doesn’t propagate eastward also forces a reasonable MJO response. Therefore, it appears that the MJO is most sensitive to the existence of low-level heating and not necessarily its vertical tilt or propagation, at least in CAM4. Additional runs attempt to isolate the environmental response to a low-level, non-propagating heat source in the Indian Ocean. Initial results suggest that the environment’s ability to organize convection on MJO scales in the model is not dependent on the existence of a moist mid-troposphere.