Relative Roles of Low-Level Wind Speed and Moisture in the Diurnal Cycle of Rainfall Over a Tropical Island Under Monsoonal Flows

Using satellite observations and reanalysis data, this study investigates the relative roles of low-level wind speed and moisture content in the rainfall diurnal cycle over a tropical island influenced by monsoonal winds. Results show that the spatiotemporal characteristics of rainfall over the island are evidently influenced by the two factors. Specifically, the spatial distribution of rainfall is primarily determined by the low-level wind speeds, while the rainfall diurnal cycle is influenced by both factors. Weaker low-level wind speed leads to stronger and wider inland convergence and afternoon precipitation, which are mainly produced by the inland penetrating sea breeze fronts. Nighttime rainfall over the island is closely related to the inertial oscillation. Stronger nocturnal rainfall can be found with higher low-level moisture content and stronger monsoonal winds. The multiscale interactions between the large-scale circulation, land–sea breezes, and inertial oscillation play essential roles in modulating the rainfall over this tropical island.