Large-eddy simulations of trade-wind showers over a tropical island

Shallow trade-wind cumuli lying beneath strong inversions are widespread over the tropical oceans. Emerging observations from the small mountainous Caribbean island of Dominica (15N) suggest that these clouds can rapidly build into rain showers as they make landfall even when little to no precipitation falls over the surrounding sea. The persistence of this regime leads to strong spatial variability in the island climate with a precipitation maximum on the high terrain and a pronounced lee-side rain shadow. These data also suggest that radiational heating/cooling is unimportant for triggering the showers as there is little diurnal variation in precipitation. To describe the physical mechanisms underlying the island precipitation enhancement, we conduct large-eddy simulations of trade-wind flow over an idealized ridge that capture the formation of turbulent clouds over the ocean and their subsequent evolution over land.