Prediction of Ocean Circulation Associated with the MJO during CINDY/DYNAMO by a Global Coupled Model

Abstract:

A global coupled prediction system is used to predict the ocean circulation associated with the MJO during the CINDY/DYNAMO field campaign. The ocean component of the system is HYCOM (Hybrid Coordinate Ocean Model) that uses exceptionally high horizontal resolution (1/12°) to accurately simulate the ocean circulation. The atmospheric component is NAVGEM (NAVy Global Environmental Model) with the resolution of T359L50, in which a new convection scheme is recently implemented. During the field campaign, three active episodes of large-scale convection and anomalous surface zonal winds associated with the MJO propagated eastward across the tropical Indian Ocean. Our model prediction primarily focuses on the second MJO event in November, which was particularly well monitored by the DYNAMO observational network. The model was initialized on November 1st, and integrated for 40 days, which includes the period of the initiation of MJO convection in the central Indian Ocean in late November. The model is able to predict the initiation of MJO convection, which is associated with the large-scale strong westerly winds generated near the equator. These westerlies drove strong oceanic equatorial jets in the entire tropical Indian Ocean. The timing and strength of the equatorial jet predicted by the model is consistent with those observed by the CINDY/DYNAMO moorings. Also, the spatial pattern of equatorial and off-equatorial ocean circulations in late November agrees with satellite-derived surface currents reasonably well. The impact of air-sea coupling on the prediction of equatorial westerly wind events is further discussed based on the comparison of coupled and uncoupled model simulations.