Delving into Model Resolution Impacts: The High Resolution Model Intercomparison Project (HighResMIP v1.0) for CMIP6
Robust projections and predictions of regional climate variability and change rely on a climate model’s ability to represent the driving processes with fidelity. For the first time, the High Resolution Model Intercomparison Project (HighResMIP) uses a multi-model approach to systematically investigate the impact of model horizontal resolution on climate simulations for historical and future climate states.
An international project called HighResMIP that included researchers from the Department of Energy’s Pacific Northwest National Laboratory is coordinating high resolution simulations and process-based analyses to assess the benefits of increased horizontal resolution for climate simulation. A better representation of multiple-scale interactions is essential for a trustworthy simulation of the climate, its variability, and its response to greenhouse gases, aerosols, and land-use perturbations. By investigating the relationship of model spread to small-scale processes in the atmosphere and ocean, and how well those processes are represented in climate models at low- and high-resolution, the outcomes of HighResMIP will have significant implications for understanding uncertainty in projections of regional climate change, water availability, and regional sea level rise.
With advances in high performance computing, the climate modeling community has a growing interest in evaluating how increased horizontal model resolution improves process representation in all components of the climate system. Some recent simulations at a higher resolution demonstrated improvements in representing small-scale processes and extremes as well as suggested the possibility of altering the large-scale aspects of circulation. However, high-resolution global simulations at climate timescales, with resolutions of at least 50 km in the atmosphere and 0.25 degree resolution in the ocean, have only been performed at relatively few research centers without overall modeling community coordination to facilitate systematic model comparisons. Assessing the robust response of the simulated climate to model resolution requires a large, multi-model ensemble and a coordinated set of experiments. In the High Resolution Model Intercomparison Project (HighResMIP), a coordinated set of experiments was designed to assess both a standard and an enhanced horizontal-resolution atmosphere and ocean simulation. This paper describes the experimental set-up of HighResMIP, the analysis plan, and the connection with the core set and other Model Intercomparison Projects endorsed by the Coupled Model Intercomparison Project Phase 6 (CMIP6). HighResMIP addresses a key question on the origins and consequences of systematic model spread, with a focus on their relationship to model horizontal resolution. As part of CMIP6, HighResMIP addresses the World Climate Research Program (WCRP) grand challenges.