Short- and Long-lived Break Events during the South China Sea Summer Monsoon and Their Associations with Intraseasonal Oscillations

This study conducts a comparative investigation between short-lived (3–8 days) and long-lived (9–24 days) break events of the South China Sea summer monsoon during 1979–2020, focusing on their statistical characteristics and potential mechanisms for their different persistence. Results suggest that both types of events are characterized by anomalously suppressed convection accompanied by an anomalous anticyclone during the break period. However, these convection and circulation anomalies exhibit more localized patterns for short-lived events, but possess larger spatial scales and stronger intensities for long-lived events. The influence of tropical intraseasonal oscillations (ISOs) on short- and long-lived events is explored to interpret their different durations. It is found that for short-lived events, the 10–25-day oscillation is dominant in initiating and terminating the break, while the impact of the 30–60-day oscillation is secondary, thus resulting in a brief break period. In contrast, for long-lived events, the 10–25-day oscillation contributes to break development rather than its initiation, and concurrently, the 30–60-day oscillation shows a remarkable enhancement and plays a decisive role in prolonging the break duration. Furthermore, we find that long-lived events are preceded by significant ISO activities approximately two weeks before their occurrence, which can be regarded as efficient predictors. Associated with these precursory ISOs, the occurrence probability of break days for long-lived events can rise up to triple their original probability (35.43% vs. 11.21%).