Influence of Indian Ocean Tropical Cyclones on the Development of the Madden-Julian Oscillation in December 2011

Previous studies demonstrate that the Madden-Julian Oscillation (MJO) modulates tropical cyclone (TC) activity over various locations worldwide. Since TCs are associated with anomalous large-scale circulations, they can influence the development of the MJO. However, the impact of TC on the MJO has not been thoroughly examined. This study investigates the influence of TC-associated processes on the MJO development based on the analysis of a case observed during the Dynamics of the Madden-Julian Oscillation field campaign. During the suppressed phase before the December 2011 MJO initiation, two TCs were active in the southern Tropical Indian Ocean (TIO). A dry air band within 10 degrees S-Eq is sustained by TC-induced horizontal advection and descent, inhibiting large-scale convection in the southern equatorial IO. Consequently, convection is triggered and develops only in the northern TIO around Eq-10 degrees N. The MJO initiates as convection develops south of the equator after the TCs dissipate.