Science Drivers

Using the nonhydrostatic CESM3-CAM-SE-NH configuration with kilometer-scale grid spacings we will advance the scientific understanding of scale interactions via selected exemplars. The land, oceans, and the atmosphere interact on a wide range of temporal and spatial scales which, for example, take place through exchanges of momentum and heat at their interfaces and via topographic forcing. These interactions play fundamental roles in shaping the mean state of the Earth system, its variability and change. Meanwhile, the importance of mesoscale interactions (down to the km scale) and the impediments of atmospheric deep convection parameterizations have been widely recognized (Satoh et al. 2019). This motivates our selected scientific exemplars and overarching science questions:

1. Will the nonhydrostatic CESM-CAM-SE-NH configuration enable the realistic evolution of extreme precipitation events, such as Mesoscale Convective Systems (MCSs), and truthfully represent their interactions with the large-scale flow over long (non-weather) time scales?

2. How will simulations of tropical precipitation and tropical cyclones be impacted by permitting multi-scale ocean-atmosphere interactions at cloud-permitting and ocean-eddy-permitting resolutions?

Our goal is to demonstrate that the nonhydrostatic CESM-CAM-SE configuration will advance the scientific understanding of mesoscale land-atmosphere interactions in the midlatitudes and air-sea interactions in tropical regions. We pick MCSs over the CONUS domain, and tropical precipitation and tropical cyclones as the primary scientific foci to highlight the benefits of the cloud-permitting modeling capability. This will include open questions how MSCs interact with planetary-scale Rossby waves and the 250 hPa jet stream.