Role of tropical intraseasonal oscillations in the South China Sea summer monsoon withdrawal in 2010

Based on the ensemble empirical mode decomposition of low-level winds and outgoing longwave radiation, this paper analyzes the influence of tropical intraseasonal oscillations (ISOs) on one extremely late case of South China Sea (SCS) summer monsoon withdrawal (SMW). Compared to the climatological monsoon withdrawal of September 25, the South China Sea summer monsoon withdrawal in 2010 was delayed for approximately 1 month (October 26) and is the latest in the past 60 years. The quasi-biweekly oscillation (QBWO) and Madden-Julian oscillation (MJO) originating from the equatorial Indian Ocean propagate northeastward to the SCS. The accompanying circulation first induced a westerly burst event and prolonged the lifespan of the summer monsoon. After this transitory recovery, the circulation anomalies associated with the current propagation of ISOs into the SCS contributed to the large-scale circulation adjustment, leaded to the shift of zonal wind (from westerlies to easterlies) and triggered the SCSSM withdrawal. This case study shows that, in addition to the well-studied impacts of ISOs on the monsoon onset and active/break cycle, the ISOs can also trigger the monsoon withdrawal.