Tropical rainfall simulated by a convection-permitting ocean-atmosphere coupled regional model

The Maritime Continent is the largest archipelago in the world and a region of intense convective activity that influences the Earth’s large-scale dynamics. Deep convective clouds generated over the islands generate large amounts of rainfall and inject moisture and energy in the upper troposphere, which are then distributed globally through the Hadley cell and the Walker circulation. Despite the local and the global importance of convective processes in the region, atmospheric models show some fundamental errors in their simulation, which are then reflected in rainfall.

Besides limitations in the way we represent convection in models, the region features one of the warmest oceans, land-ocean thermal contrasts, very complex topography, dense tropical vegetation and a wide range of island sizes that pose further challenges to atmospheric climate models. A few avenues have been proposed for better representing these forcings and processes, and thus improving the simulation of rainfall, such as the use of convection-permitting models that do not require convective parameterization and the coupling of ocean and atmosphere models.

In this talk, I will discuss the effects of the model spatial resolution and the convective representation on the Maritime Continent rainfall characteristics. I will also show the impact of explicitly resolving convection on the vertical structure of the atmosphere and how it results in different precipitation patterns. Using a Pseudo Global Warming approach, I will show how these differences may extend to future projections and will discuss the response of the Maritime Continent rainfall to climate change using different convective representations. Finally, I will present our latest results from the first convection-permitting ocean-atmosphere coupled simulations in the region and give some insight on their potential for improved precipitation diurnal cycle both over land and ocean.