82 / 2021-07-16 22:24:42

Impact of islands on the MJO propagation across the Maritime Continent - a numerical modeling study of an MJO event

MJO,Maritime Continent,Barrier effect,Cloud-permitting simulation

A case study of the MJO event observed during January and February 2017 is conducted to understand its propagation through the Maritime Continent (MC) region. Ensemble cloud-permitting numerical simulations are performed to test the effects of the islands over MC on this MJO event. The control simulation reasonably captures the large-scale mean state, eastward propagation and diurnal cycle over islands of this MJO event. Sensitivity experiments are conducted to test the impact of topography, friction, and land-sea contrast on this MJO event. Eliminating the topography around the MC region leads to reduced precipitation over the islands while changes in eastward propagation are small. When friction is further removed, results are similar except that the low-level wind is stronger, and the MJO precipitation propagation is not essentially different. Land-sea contrast is further eliminated by replacing land with ocean, and the MJO is stronger and displays smoother eastward propagation. Diagnosis of moist static energy budget indicates that both the surface flux feedback and horizontal advection (especially the zonal advection) are greatly strengthened without land-sea contrast, which enhance the convection over the sea and facilitate the eastward propagation of the MJO.