11.5 Mesoscale vs. Global Physics Suites: Differing Approaches and Parameterization Behavior

Gustafson Jr., William I., Po-Lun Ma, Balwinder Singh,  Jerome D. Fast, and Philip J. Rasch; Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory

No matter the scale simulated, all non-idealized atmospheric models must account for physical processes such as turbulence, radiation, and clouds. However, modeling at different scales requires different approaches. A large eddy simulation (LES) handles clouds differently than a global climate model, and a mesoscale model lies between these two extremes. At one end of this spectrum, one can view bulk cloud processes as practically resolved, but at the other end they are entirely parameterized. Even so, micro-scale processes, such as condensation, must be parameterized at all practical grid spacings. The continuum of atmospheric models requires careful consideration of the scales involved and the best way to handle each process for the given scale. Today, WRF contains physics modules designed for the full model spectrum, from the eddy-scale to the global-scale. What are the differences between the approaches used in the schemes? How do cloud schemes designed for global resolutions behave at finer scales? This presentation will give an update on implementation of the Community Atmospheric Model v5 physics suite in WRF, and compare this physics suite against a traditional mesoscale physics suite to better understand how the schemes behave at mesoscale resolutions. The Separate Physics and Dynamics Setup (SPADS), which allows one to target parameterization behaviors at different scales through the use of independent dynamics and physics resolutions, will be employed to understand the scaling behavior of the two physics setups.