资源环境科技发展态势分析平台

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.

Plain Language Summary Low-level wind speed and moisture content are known to be two important factors controlling the spatiotemporal characteristics of precipitation over tropical islands. Here we explored the relative importance of these two factors in determining the rainfall diurnal cycle over a monsoonal tropical island using long-term satellite observations and reanalysis data. Results show that the spatial distribution of the island rainfall is mainly determined by low-level wind speeds. Rainfall shows a stronger afternoon peak under weaker monsoonal winds, owing to stronger inland convergence by the sea breeze fronts penetrating inland. The nocturnal rainfall is closely associated with the boundary-layer inertia oscillation and also sensitive to the low-level moisture content. Stronger nighttime rainfall can be found with higher low-level moisture content and stronger low-level monsoonal winds.