Precipitation locking along the Dabie and Tongbai Mountains during the passage of remnants of Tropical Cyclone Rumbia (2018)

When Rumbia exerted an influence over the Dabie and 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 is significant, primarily occurring along the windward slope up to the ridgeline. Whereas precipitation enhancement over the Tongbai Mountains is weaker and largely confined to the vicinity of its ridgeline. The magnitude of precipitation enhancement is closely related to terrain scale and the differential impacts of Rumbia’s outer and inner circulations. Both the outer and inner circulations are associated with intermittent convective clusters moving across the Dabie and Tongbai Mountains, which serve as seeder clouds for precipitation enhancement. Meanwhile, rainfall from Rumbia’s primary rainband moistens the low-level inflow, which is advected toward the mountains by Rumbia’s circulation. Orographic lifting and blocking lead 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, exert stronger lifting and blocking effects, resulting in more favorable conditions for both seeder and feeder clouds. Furthermore, Rumbia’s inner circulation is stronger than its outer circulation. When it interacts with the Dabie Mountains, it triggers localized convection, which merges with incoming convective clusters, thereby enhancing seeder cloud development and intensifying orographic precipitation.