THE INTERACTION OF EASTWARD PROPAGATING EQUATORIAL MODES WITH THE MARITIME CONTINENT

Abstract:

We examine the processes that contribute to blocking of the eastward propagating equatorial modes by the Maritime Continent. The recent study by Baranowski at al (2015) have shown that the propgation of Kelvin waves through the Maritime Continent is strongly influenced by the interaction of the waves with the diurnnal cycle of convection over the land which can either amplify or supress the convective forcing of the wave. This suggests that inorder for the wave to cross the Maritime Continent it has to be in phase with local convection. Another possible mechanism through which the Maritime Continent can influence approaching Kelvin waves and MJO's is their interacton with cyclonic disturbances generated by the lee vortices at the tips of Sumatra. Both of these mechanisms can be misrepresented by dynamic models and contribute to predictability barrier in this region

These equatorial modes ate examined in Navy models forecasts of DYNAMO MJOs and n idealized experiments. While the models appear to predict the MJO and Kelvin wave approach to the Maritime continent their propagation is too slowa andn westward propagating disturbance are often too strong. We examine the contribution of lee vortices and local diurnal convection variability to this process