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

Abstract

Abstract. 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× 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 region, extratropical cyclones, and spatial variability in land hydrological processes. The improvements over land are related to the better-resolved topography in NARRM, whereas those over ocean are attributable to the improved air–sea interactions with finer grids for both atmosphere and ocean and sea ice. Some features appear insensitive to the resolution change analyzed here, for instance the diurnal propagation of organized mesoscale convective systems over CONUS and the warm-season land–atmosphere coupling at the southern Great Plains. In summary, our study presents a realistically efficient approach to leverage the fully coupled RRM framework for a standard Earth system model release and high-resolution climate production simulations.

Recreating the California New Year's Flood Event of 1997 in a Regionally Refined Earth System Model

“…However, a general high bias in reservoir inflows was found across RRM‐E3SM simulations and agrees with the general high bias in California DJF mean streamflow identified in Tang et al. (2022).…”

“…The Energy Exascale Earth System Model version 2 (E3SMv2; Golaz et al., 2022) used for this analysis allows for regionally refined mesh (RRM‐E3SM) simulations over a targeted region of interest. Recent studies find that RRM‐E3SM performs comparably to uniform 0.25° (∼25 km) horizontal resolution simulations for water cycle‐related processes and provides several improvements to uniform 1.00° (∼111 km) horizontal resolution simulations (Tang et al., 2019, 2022). These improvements include a better representation of winter‐time precipitation rates and cloud properties over the contiguous United States, higher extratropical cyclone activity in the north Pacific, and snowpack accumulation rates and peak timing and volumes in the California Sierra Nevada compared with ∼111 km simulations.…”

“…More specific findings related to RRM‐E3SM are described in Tang et al. (2022), while Harrop et al. (2022) provides additional details on water cycle process fidelity in both the atmosphere and land‐surface in E3SM at uniform horizontal resolutions of 1.00° versus 0.25° over the United States.…”

Influence of Eastern Pacific Hurricanes on the Southwest US Wildfire Environment

“…The resolution of the ocean and sea ice models on the other hand varies between 14 and 60 km with 60 vertical layers in the ocean model. For further details regarding the model physics and parameterizations employed, see Tang et al (2022). Three ensemble members of historical E3SM simulations, using the NARRM configuration are used in this study.…”

ENSO Diversity and the Simulation of Its Teleconnections to Winter Precipitation Extremes Over the US in High Resolution Earth System Models

“…We evaluate 100‐year 1950‐control simulations with fully coupled HR (25–50 km atmosphere model nominal resolutions) version of E3SM1 and five models (CNRM‐CM6‐1, EC‐Earth‐3P, ECMWF‐IFS, HadGEM3‐GC31, and MPI‐ESM1‐2) participating in the HighResMIP activity (Haarsma et al., 2016) with daily precipitation data available in the CMIP6 archive (Eyring et al., 2016). We also evaluate a segment (1950–2014) of a historical simulation conducted with the North American Regionally Refined Model version of E3SM2, where the atmosphere model nominal resolution over North America and the surrounding oceans is 25 km, and decreases to 100 km elsewhere (Tang et al., 2022). We also compare these HR simulations against their counterpart low resolution (50–250 km atmosphere model nominal resolution) production model simulations.…”