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Public Release of Two FMS-Based Ocean Models: The Massively Parallelized Modular Ocean Model and a Novel Isopycnal Coordinate Model
3rd Quarter GFDL Milestone - FY02
Purpose:
The goal of this milestone is to provide the international community of ocean and climate modelers with version 4 of the Modular Ocean Model (MOM4) and version 1 of the Hallberg Isopycnal Model (HIM1). Both models are designed for massively parallel systems, yet are suitable for a variety of other computational platforms.
MOM4 and HIM1 represent the state-of-the-art for the two most widely used classes of global ocean climate models. MOM4 uses the computational software infrastructure and superstructure provided by GFDL's Fortran-based Flexible Modeling System (FMS), and HIM1 is based on an analogous C-based software design. Both ocean models contain numerical methods and physical parameterizations that produce physically robust global ocean climate simulations. The availability of these two models provides the ocean research community with a unique and powerful facility for evaluating the integrity of climate sensitivities and thus reducing uncertainties in climate predictions.
Efforts:
A concentrated effort to develop MOM4 and HIM1 has taken place over the past few years. This effort involved a focused commitment by members of GFDL's Ocean Model Development Team and Modeling Services. A key focus of this effort was to ensure that the two models have a complete suite of functionalities needed for a wide variety of studies, ranging from idealized geophysical fluid dynamics experiments to fully coupled earth system models.
Customers:
The principal customers of these two models are scientists interested in building and using ocean models and coupled earth system models, both for fundamental and applied research and development purposes.
Significance:
MOM4 represents a major upgrade in computational flexibility relative to earlier model versions. Enhancements to the numerics and physical parameterizations of the model provide increased confidence in the physical integrity of the simulations.
HIM1 includes robust treatments of the complete range of physical processes controlling the large-scale ocean circulation. It provides ocean modelers with innovative and improved numerical techniques to address several areas of known difficulty with other models of its class, such as the nonlinear equation of state and the surface mixed layer
Success:
A beta version of MOM4 was released to the ocean modeling research community on April 26, 2002 and HIM1 was released on June 30, 2002. Both model releases include three test cases. Many tens of researchers internationally are testing the codes on a variety of computer platforms and for a wide range of purposes. In particular, MOM4 and HIM1 are being used in the next-generation version of GFDL's global ocean climate simulations, as well as in extremely high-resolution hemispheric and global simulations. An example of a Southern Hemisphere simulation with HIM is shown in Figure 1. Here, results from two model resolutions illustrate the enhanced realism of the complex ocean current structure achieved at high resolution in simulations of the Antarctic Circumpolar Current.
Next Steps:
Revisions of MOM4 will be released coincident with the major release schedule of GFDL's Flexible Modeling System. A Fortran 90 version of HIM will be available in the second quarter of 2003. Subsequent revisions of HIM will then be released within the regular update cycle of FMS.
Figure 1. Speed of surface currents in two HIM1 simulations of the Antarctic Circumpolar Current ( ACC ) at different resolutions. ( The magnitude of the current speed is displayed on a logarithmic scale in order to more easily highlight regions of peak currents. ) The ACC is the strongest of the world's current systems. The figure shows highly irregular turbulent structures whose details become far more realistic in the refined resolution simulation shown in the right panel.