Determining resolution awareness of microphysics using the separate physics and dynamics experiment framework

Description

This poster presents results from a recently submitted paper showing the utility of the Separate Physics and Dynamics Experiment (SPADE) framework for examining resolution dependencies within atmospheric model physics parameterizations. As a first demonstration of SPADE, an analysis has been performed comparing the resolution dependence of microphysics designed for a mesoscale model versus one designed for a global climate model. Specifically, the Morrison microphysics from the Weather Research and Forecasting (WRF) model is compared with the Morrison-Gettelman microphysics from the Community Atmosphere Model v5 (CAM5).

The comparison is done using a month-long, springtime simulation for the central United States coinciding with the Midlatitude Continental Convective Clouds Experiment (MC3E). Grid spacings of 4 and 32 km are compared to span the “gray zone” of cloud parameterization, which is in the range targeted for global cloud-system resolving models and current state-of-the-art climate models. Understanding the resolution dependence of parameterizations within this range is critical for improving next-generation climate models with multi-resolution grids, as well as uniform high-resolution grids.

The SPADE framework complements traditional resolution-dependence comparisons. In a traditional comparison, the grid spacing is changed for all model components, and a comparison is done to see how model behavior changes with resolution. For SPADE, the grid spacing is held constant for most of the model while changing the grid spacing for specific components of interest. This allows one to isolate specific resolution dependencies within the model, making it easier to understand the dependencies for the tested components.