Journal Article

The DOE E3SM Coupled Model Version 1: Description and Results at High Resolution

Feng, Yan, Li, Qing, Maltrud, Mathew E., Wolfe, Jonathan D., Jacob, Robert, Pinheiro, Marielle, Qian, Yun, Ullrich, Paul A., Zhou, Tian, Lin, Wuyin, Golaz, Jean‐Christophe, Dong, Lu, Leung, L. Ruby, Klein, Stephen A., Bader, David C., Balaguru, Karthik, Li, Hong‐Yi, Roberts, Andrew F., Taylor, Mark A., Tang, Qi, Wang, Hailong, Xie, Shaocheng, Neale, Richard B., Yang, Yang, Zhang, Kai, Mametjanov, Azamat, Keen, Noel D., Van Roekel, Luke P., Caldwell, Peter M., Liu, Xiaohong, Veneziani, Milena, Zhang, Yuying, Cameron‐Smith, Philip

2019

Overview

This study provides an overview of the coupled high‐resolution Version 1 of the Energy Exascale Earth System Model (E3SMv1) and documents the characteristics of a 50‐year‐long high‐resolution control simulation with time‐invariant 1950 forcings following the HighResMIP protocol. In terms of global root‐mean‐squared error metrics, this high‐resolution simulation is generally superior to results from the low‐resolution configuration of E3SMv1 (due to resolution, tuning changes, and possibly initialization procedure) and compares favorably to models in the CMIP5 ensemble. Ocean and sea ice simulation is particularly improved, due to better resolution of bathymetry, the ability to capture more variability and extremes in winds and currents, and the ability to resolve mesoscale ocean eddies. The largest improvement in this regard is an ice‐free Labrador Sea, which is a major problem at low resolution. Interestingly, several features found to improve with resolution in previous studies are insensitive to resolution or even degrade in E3SMv1. Most notable in this regard are warm bias and associated stratocumulus deficiency in eastern subtropical oceans and lack of improvement in El Niño. Another major finding of this study is that resolution increase had negligible impact on climate sensitivity (measured by net feedback determined through uniform +4K prescribed sea surface temperature increase) and aerosol sensitivity. Cloud response to resolution increase consisted of very minor decrease at all levels. Large‐scale patterns of precipitation bias were also relatively unaffected by grid spacing. Plain Language Summary The Energy Exascale Earth System Model (E3SM) is a relatively new fully coupled Earth system and climate model used in major international model simulation projects and mission‐defined efforts for the U.S. Department of Energy. This paper describes the first simulation of the model in its high‐resolution configuration. This higher‐resolution version is able to capture the most energetic motions in the ocean, which are poorly represented in standard resolution coupled climate models, as well as the largest of storms in the atmosphere. Evaluation of this simulation confirms the benefits of high resolution found by other models with a few notable exceptions. These discrepancies with other studies are interesting because they provide a richer understanding of how and why resolution affects model bias. Another key finding is that climate and aerosol sensitivity in E3SM is unaffected by resolution change. This affirms the usefulness of coarser‐resolution models for understanding global‐scale climate change. This study also confirms the benefits of increased resolution for studying fine‐scale features such as hurricanes and orographic precipitation. Finally, the high‐resolution version of E3SM is shown to compare favorably to its low‐resolution counterpart and to the models participating in Phase 5 of the Coupled Model Intercomparison Project. Key Points The high‐resolution E3SMv1 model was run for 50 years using 1950 forcing data according to the HighResMIP protocol Higher resolution and associated retuning improved bias relative to coarser versions of E3SMv1, particularly in ocean and sea ice metrics Aerosol and climate sensitivity were relatively unaffected by resolution change; resolution‐related tuning had a larger impact

• Publisher: John Wiley & Sons, Inc,American Geophysical Union (AGU)
• Subject: Bathymetry / Climate sensitivity / Earth / Eddies / El Nino / El Nino phenomena / ENVIRONMENTAL SCIENCES / Ocean circulation / Oceanic eddies / Oceans / open climate campaign / Resolution / Sea ice / Sea surface / Sea surface temperature / Simulation / Temperature rise / Winds