U.S. Department of Energy Office of Biological and Environmental Research

BER Research Highlights


Reduced Spurious Vertical Mixing in MPAS-Ocean Model
Published: December 24, 2014
Posted: May 23, 2016

In the ocean, vertical diffusion is several orders of magnitude smaller than horizontal diffusion. Ocean models have difficulty in reproducing low values of vertical diffusion due to spurious mixing intrinsic to the numerical algorithms. Recent work supported by the Department of Energy shows that spurious vertical mixing may be reduced by several advanced techniques.

The Model for Prediction Across Scales-Ocean (MPAS-Ocean) was validated against five long-standing ocean models using five domains, ranging from simple idealized test cases to real-world simulations. MPAS-Ocean produces results commensurate with the other models, validating the functionality of the new model. In addition, MPAS-Ocean produced less spurious mixing than other models, by up to a factor of ten, as measured by the resting potential energy. This result is due to a combination of the vertical coordinate, hexagon-type horizontal grid, and a tracer advection scheme designed for these grids. Ocean models are often categorized by their vertical coordinate. The Arbitrary Lagrangian-Eulerian method (ALE) of the MPAS-Ocean model offers great flexibility, so users can choose from numerous vertical coordinates: z-level (fixed), z-star (expands with sea surface), z-tilde (grid moves with fast waves), sigma (terrain-following), and idealized isopycnal (density surfaces). All of these modes were validated in idealized test cases and compared to other ocean models, including the Parallel Ocean Program (POP), Modular Ocean Model (MOM), MIT General Circulation Model (MITgcm), Regional Ocean Modeling System (ROMS), and Hallberg Isopycnal Model (HIM). The z-type coordinates were validated using real-world cases. MPAS-Ocean performed similarly or better than long-standing ocean models, and certain configurations of the vertical coordinate dramatically reduced the spurious mixing. Thanks to improved algorithms, MPAS-Ocean will better represent physical mixing processes in climate simulations, leading to more accurate climate studies.

Reference: Petersen, M.R., D. W. Jacobsen, T. D. Ringler, M. W. Hecht, and M. E. Maltrud. 2015. “Evaluation of the Arbitrary Lagrangian–Eulerian Vertical Coordinate Method in the MPAS-Ocean Model,” Ocean Modelling 86, 93–113. DOI: 10.1016/j.ocemod.2014.12.004. (Reference link)

Contact: Dorothy Koch, SC-23.1, (301) 903-0105
Topic Areas:

  • Research Area: Earth and Environmental Systems Modeling

Division: SC-23.1 Climate and Environmental Sciences Division, BER

 

BER supports basic research and scientific user facilities to advance DOE missions in energy and environment. More about BER

Recent Highlights

May 10, 2019
Quantifying Decision Uncertainty in Water Management via a Coupled Agent-Based Model
Considering risk perception can improve the representation of human decision-making processes in age [more...]

May 09, 2019
Projecting Global Urban Area Growth Through 2100 Based on Historical Time Series Data and Future Scenarios
Study provides country-specific urban area growth models and the first dataset on country-level urba [more...]

May 05, 2019
Calibrating Building Energy Demand Models to Refine Long-Term Energy Planning
A new, flexible calibration approach improved model accuracy in capturing year-to-year changes in bu [more...]

May 03, 2019
Calibration and Uncertainty Analysis of Demeter for Better Downscaling of Global Land Use and Land Cover Projections
Researchers improved the Demeter model’s performance by calibrating key parameters and establi [more...]

Apr 22, 2019
Representation of U.S. Warm Temperature Extremes in Global Climate Model Ensembles
Representation of warm temperature events varies considerably among global climate models, which has [more...]

List all highlights (possible long download time)