Indispensable Role of the Madden‐Julian Oscillation in the 2019 Extreme Autumn Drought Over Eastern China
Li Qi, Yue Ji, Wenjun Zhang
Abstract
Abstract Eastern China suffered an extensive drought during autumn (September–October 2019) with precipitation deficits reaching as high as 70% of the climatology, the worst on record since the 1980s. Concurrent with this extreme drought, the tropical Indo–Pacific oceans experienced a central–Pacific (CP) El Niño event with the westernmost location, and the third–ranking positive Indian Ocean Dipole (IOD) event. However, the CP El Niño associated convection anomalies are unexpectedly absent over the western equatorial Pacific, leading to the decoupling of traditional atmospheric–oceanic connections between the tropical Pacific and Indian Oceans. A strong Madden–Julian oscillation (MJO) event stayed in the western Indian Ocean for 32 days during September–October 2019, nearly triple the frequency of climatology. This extraordinary long–lasting MJO activity suppressed the western Pacific convection associated with the CP El Niño and simultaneously enhanced the local IOD–related sea surface temperature anomalies via the atmospheric forcing. The MJO associated convection over the Indian Ocean can excite an anomalous cyclone in the western North Pacific, producing persistently extensive precipitation deficiencies over eastern China. It highlights that the abnormal MJO activity plays a crucial role on the Indo–Pacific atmospheric–oceanic features and the extreme precipitation deficits over eastern China.