Western North Pacific tropical cyclones suppress Maritime Continent rainfall

It is generally believed that the Maritime Continent (MC) is rarely affected by tropical cyclones (TCs) due to its equatorial location. However, this study reveals that TCs in the tropical western North Pacific can significantly suppress rainfall over the MC and its surrounding seas, based on the composite analysis. This suppression effect of TCs exists across all phases of the Madden–Julian Oscillation (MJO). TCs greatly alleviate rainfall enhancement during the convective phases of the MJO and aggravate rainfall suppression during the suppressive phases. Particularly, TCs reduce the likelihood of extremely high rainfall in convective MJO phases from 9% to 5% and increase the likelihood of extremely low rainfall in suppressive MJO phases from 10% to 16%. The rainfall suppression is attributed to the lower-tropospheric southwesterly anomalies to the south of TCs, which result in moisture divergence over the MC. Additionally, the upper-tropospheric equatorward outflows of TCs also promote subsidence and suppress rainfall. This study introduces a new factor influencing the rainfall over the MC from a synoptic climatology perspective.