Precipitation Locking along the Dabie and Tongbai Mountains during the Passage of Remnants of Tropical Cyclone Rumbia (2018)

When Tropical Cyclone Rumbia (2018) exerted an influence over the Dabie Mountains and the Tongbai Mountains, its track was positioned to the northeast of the two mountain ranges and remained approximately parallel to their ridgelines, and the primary rainband of Rumbia lay outside these mountains. This study investigates the heavy precipitation processes induced by the Dabie and Tongbai Mountains during this period. It is found that precipitation enhancement over the Dabie Mountains was significant, primarily occurring along the windward slope up to the ridgeline. Whereas, precipitation enhancement over the Tongbai Mountains was weaker and largely confined to the vicinity of its ridgeline. The magnitude of precipitation enhancement was closely related to the terrain scale and the differential impacts of Rumbia’s outer and inner circulations. Both the outer and inner circulations were associated with intermittent convective clusters moving across the Dabie and Tongbai Mountains, which served as seeder clouds for precipitation enhancement. Meanwhile, rainfall from Rumbia’s primary rainband moistened the low-level inflow, which was advected toward the mountains by Rumbia’s circulation. Orographic lifting and blocking led to the formation and accumulation of low-level cloud water, providing a source of feeder clouds. The Dabie Mountains, being broader and higher than the Tongbai Mountains, exerted stronger lifting and blocking effects, resulting in more favorable conditions for both seeder and feeder clouds. Furthermore, Rumbia’s inner circulation was stronger than its outer circulation. When it interacted with the Dabie Mountains, it triggered localized convection, which merged with incoming convective clusters, thereby enhancing seeder cloud development and intensifying orographic precipitation.