June persistence barrier of tropical land precipitation and its relationship with ENSO

Tropical land precipitation(TLP) plays a crucial role in tropical ecosystems, human activities and regional energy and hydrological cycles. To improve the predictability of TLP, it is essential to understand not only its variability but also its temporal persistence, which is a fundamental aspect of climate predictability. However, the persistence characteristics of TLP remain understudied. Using multiple precipitation datasets, this study reveals a rapidly declines in TLP persistence in June, regardless of the initial month. This phenomenon, termed the June persistence barrier (PB), is robust across datasets. Further analysis shows that sea surface temperature (SST) anomalies in the central and eastern tropical Pacific, associated with the El Niño–Southern Oscillation (ENSO), are the primary driver of the June TLP PB. ENSO-related SST exhibits a PB in May–June. When the linear influence of ENSO is removed, the TLP PB disappears, and persistence weakens significantly. Mechanistically, SST primarily affects the large-scale Walker circulation, which in turn causes quasi-consistent changes in vertical motion over tropical land. These changes directly influence local moisture transport, ultimately leading to TLP anomalies. The seasonal persistence of SST enables a sustained remote influence through the atmospheric bridge, linking oceanic variability to land precipitation. These findings not only deepen our understanding of the intrinsic variability of TLP but also provide a potential theoretical basis for the future seasonal prediction of TLP using its persistence.