Abstract

This study aims to advance the understanding of the pre-existing weather regimes up to two weeks ahead of rain belt events during the East Asian summer monsoon season. To this end, we backtrack the moisture trajectories for the rain belt events and classify up to 15 clusters of rain belt events using curve clustering. The clustered moisture channels reveal four main corridors from the Somali Jet, South Asia, Bay of Bengal and the Pacific Ocean, which are associated with different rain belt event characteristics and moisture sources. Pre-existing weather regimes, such as the zonal oscillation of the western North Pacific subtropical high, a South Asian Low, a dual-anticyclone pattern, tropical cyclones and circumglobal wave trains, are attributable to the preconditioning for rain belt events. Findings from this work may offer insights into the sources of predictability, model evaluation and short-term prediction on rain belt events in East Asia.