Observational data from Taiwan’s dense rainfall network reveal that tropical island mountain regions exhibit multiple precipitation peaks during summer afternoon convection—a finding that contrasts with the previously assumed single-peak behavior and suggests more intricate underlying processes. To investigate these multi-peak characteristics, NTU researchers designed an idealized terrain setup integrating ocean, plain, and mountainous features. Using a high-resolution (100-meter) Vector Vorticity Equation Model (VVM) developed by Professor Jianming Wu’s team, the study successfully reproduced the dual-peaked precipitation pattern locked by local topography.
The simulation results indicate that the first peak is predominantly driven by convective available potential energy (CAPE), while the second peak results from enhanced low-level moist static energy (MSE) transport by island-scale circulations. Notably, the study found that under drier free-atmosphere conditions, local circulations can intensify the second peak’s precipitation—a sensitivity that diverges from previous expectations. Furthermore, the interaction between the two convective peaks appears critical: the initial convective burst modifies environmental humidity and energy distribution, thereby influencing the intensity and structure of subsequent convection.
This research provides a novel perspective on tropical island afternoon convection and has significant implications for future studies on the impacts of climate change on extreme precipitation events. The NTU team plans to extend this work by integrating real-world topography and field observations to further validate their findings and offer more accurate scientific support for mitigating extreme weather challenges.