Shi et al. (2026) Improving simulation of Earth system variability through weakly coupled ocean data assimilation in E3SM

Identification

• Journal: Geoscientific model development
• Year: 2026
• Date: 2026-08-27
• Authors: Pengfei Shi, Lai-Yung Ruby Leung, Zhaoxia Pu, Samson Hagos, Karthik Balaguru
• DOI: 10.5194/gmd-19-8003-2026

Research Groups

• Atmospheric, Climate, and Earth Sciences Division, Pacific Northwest National Laboratory, Richland, Washington, USA (Pengfei Shi, L. Ruby Leung, Zhaoxia Pu, Samson Hagos, Karthik Balaguru)
• Department of Atmospheric Sciences, University of Utah, Salt Lake City, Utah, USA (Zhaoxia Pu)

Short Summary

This study evaluates the impact of a newly developed weakly coupled ocean data assimilation system within the DOE Energy Exascale Earth System Model version 2 (E3SMv2) on global and regional climate variability. The results demonstrate substantial improvements in simulating both interannual and decadal climate variability.

Objective

• Evaluate the effectiveness of a weakly coupled ocean data assimilation system in improving the simulation of global and regional climate variability within the E3SMv2 framework.
• Assess the impact of assimilating monthly ocean temperature and salinity from the EN4.2.1 reanalysis on simulating interannual and decadal climate modes.

Study Configuration

• Spatial Scale: Global, with a focus on tropical Pacific and regional climates over the contiguous United States.
• Temporal Scale: Seasonal-to-decadal timescales (1950-2021).

Methodology and Data

• Models used: E3SMv2, a fully coupled Earth system model.
• Data sources: EN4.2.1 reanalysis for ocean temperature and salinity.

Main Results

• The assimilation experiment exhibits markedly enhanced interannual correlations with observations for global mean surface air temperature and precipitation anomalies.
• Improved phase agreement with observations is found in the temporal variability of key climate modes, including ENSO, the Indian Ocean Dipole, and multidecadal variability in the Pacific and Atlantic Oceans.
• Regional evaluation over the contiguous United States shows enhanced skill in simulating winter surface air temperature and precipitation.

Contributions

• This study underscores the critical role of coupled forecasts in the data assimilation cycle for propagating observational information across Earth system components.
• The WCODA system enables cross-component information exchange among the ocean, atmosphere, and land, thereby generating dynamically consistent initial conditions that support more accurate simulations of Earth system variability.

Funding

• This research was supported by the U.S. Department of Energy (DOE) under contract DE-AC05-76RL01830.
• The Pacific Northwest National Laboratory is operated for DOE by Battelle Memorial Institute.
• Additional funding was provided by the National Science Foundation (NSF).

Citation

@article{Shi2026Improving,
  author = {Shi, Pengfei and Leung, Lai-Yung Ruby and Pu, Zhaoxia and Hagos, Samson and Balaguru, Karthik},
  title = {Improving simulation of Earth system variability through weakly coupled ocean data assimilation in E3SM},
  journal = {Geoscientific model development},
  year = {2026},
  doi = {10.5194/gmd-19-8003-2026},
  url = {https://doi.org/10.5194/gmd-19-8003-2026}
}