Final Report for Collaborative Project: Sensitivity of Atmospheric Parametric Formulations to Regional Mesh Refinement in Global Climate Simulations Using CESM-HOMME

In this project we analyze climate simulations using the Community Earth System Model (CESM) in order to determine the modeled response and sensitivity to horizontal resolution. Simple aqua-planet configurations were used to provide a clean comparison of the response to resolution in CESM. This enables us to easily examine all aspects of the model sensitivity to resolution including mean quantities, variability and physical parameterization tendencies: the chief reflection of resolution sensitivity. An extension to the global resolution sensitivity study is the examination of regional grid refinement where resolution changes are prescribed in a single global simulation. We examine the relevance of the global resolution sensitivity results as applied to these regional refinement simulations. In particular we examine how variations in the grid resolution, centered on different parts of the globe, lead to differences in the parameterized response and the potential to generate residual circulations as a result. Given the potential to generate this resolution sensitivity we examine simple modifications to the parameterized physics that are able to moderate any residual circulations. Finally, we transfer the framework to the standard AMIP configuration to examine the resolution sensitivity in the presence of compounding effects such as land-sea distributions, orography and seasonal variation.