The fully coupled regionally refined model of E3SM version 2: overview of the atmosphere, land, and river results

• Published in: Geoscientific Model Development
• Main Authors: Q. Tang, J.-C. Golaz, L. P. Van Roekel, M. A. Taylor, W. Lin, B. R. Hillman, P. A. Ullrich, A. M. Bradley, O. Guba, J. D. Wolfe, T. Zhou, K. Zhang, X. Zheng, Y. Zhang, M. Zhang, M. Wu, H. Wang, C. Tao, B. Singh, A. M. Rhoades, Y. Qin, H.-Y. Li, Y. Feng, C. Zhang, C. S. Zender, S. Xie, E. L. Roesler, A. F. Roberts, A. Mametjanov, M. E. Maltrud, N. D. Keen, R. L. Jacob, C. Jablonowski, O. K. Hughes, R. M. Forsyth, A. V. Di Vittorio, P. M. Caldwell, G. Bisht, R. B. McCoy, L. R. Leung, D. C. Bader
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2023
• Subjects: Geology; QE1-996.5; North Pole; Sea ice
• Online Access: https://doi.org/10.5194/gmd-16-3953-2023; https://doaj.org/article/c74f48bbdf6b4f03a5dd135d9bc43a71

This paper provides an overview of the United States (US) Department of Energy's (DOE's) Energy Exascale Earth System Model version 2 (E3SMv2) fully coupled regionally refined model (RRM) and documents the overall atmosphere, land, and river results from the Coupled Model Intercomparison Project 6 (CMIP6) DECK (Diagnosis, Evaluation, and Characterization of Klima) and historical simulations – a first-of-its-kind set of climate production simulations using RRM. The North American (NA) RRM (NARRM) is developed as the high-resolution configuration of E3SMv2 with the primary goal of more explicitly addressing DOE's mission needs regarding impacts to the US energy sector facing Earth system changes. The NARRM features finer horizontal resolution grids centered over NA, consisting of 25 → 100 km atmosphere and land, a 0.125 ∘ river-routing model, and 14 → 60 km ocean and sea ice. By design, the computational cost of NARRM is ∼ 3 × <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="28pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="abc0464bce5d23ec3bda0eaca50f539a"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="gmd-16-3953-2023-ie00001.svg" width="28pt" height="10pt" src="gmd-16-3953-2023-ie00001.png"/></svg:svg> of the uniform low-resolution (LR) model at 100 km but only ∼ 10 %–20 % of a globally uniform high-resolution model at 25 km. A novel hybrid time step strategy for the atmosphere is key for NARRM to achieve improved climate simulation fidelity within the high-resolution patch without sacrificing the overall global performance. The global climate, including climatology, time series, sensitivity, and feedback, is confirmed to be largely identical between NARRM and LR as quantified with typical climate metrics. Over the refined NA area, NARRM is generally superior to LR, including for precipitation and clouds over the contiguous US (CONUS), summertime marine stratocumulus clouds off the coast of California, liquid and ice phase clouds near the North Pole ...