Aquaplanet hydrologic cycle sensitivities to climate change and model physics, resolution, and configuration

Aquaplanet configurations are a fundamental component within the climate model hierarchy. They reduce complexities of the Earth system while maintaining a reasonable resemblance to Earth's climate and thus can reveal intrinsic properties of global circulation and precipitation. In this project, we leverage the Community Atmosphere Model (CAM) aquaplanet framework to explore sensitivities of the hydrologic cycle to model configuration in both present-day and global warming climate settings. We seek to better understand the response of the hydroclimate to choice of model physics (CAM4, CAM5.3, and next-generation CAM for CESM2), horizontal grid resolution within a limited range (2° and 1°), and ocean type (fixed-SST or slab ocean). Preliminary results based on present-day simulations indicate a) persistent light-rain model biases both in the tropics and extratropics, where precipitation is expected to be better resolved, and b) large sensitivities of tropical precipitation distribution to choice of grid resolution, with the nature of the response being physics-dependent. Such results may have important implications for the interpretation of precipitation distributions and extremes in future climate projections.