1. An Introduction to WGOMD Stephen Griffies NOAA/GFDL/Princeton USA Working Group for Ocean Model Development (WGOMD) Presentation to WGOMD 25 August 2007 Bergen, Norway

2. WGOMD Terms of Reference (as of 2000 with slight revision 2005) To stimulate the development of ocean models for research in climate and related fields. (recently deleted qualifier: “with a focus on decadal and longer timescales at mid-and high-latitudes.”) To encourage investigations of the effects of model formulation on the results of ocean models, making use of sensitivity studies and intercomparisons. To promote interaction amongst the ocean modelling community and between this and other communities through workshops and other activities. To stimulate the validation of ocean models when used in stand alone mode and as part of a coupled ocean-atmosphere model, using oceanographic data and other methods, and to advise on the observational requirements of such studies. To publicise developments in ocean models amongst the climate modelling community. To collaborate with other activities in areas of overlapping responsibility. To advise on ocean modelling and related issues and to report on its activities to the JSC/CLIVAR WGCM and CLIVAR Scientific Steering Group. * *Two sets of parent organizations are often cumbersome for WGOMD (e.g., two different international meetings to report to each year). ToR are largely applicable today, with perhaps some modifications based on new developments in the community.

3. WGOMD Assumptions Ocean models are relevant to understanding climate and predicting potential future changes. The space-time scales relevant for WGOMD considerations extends from the global climate scale to the regional and increasingly the coastal scales. Scientifically based model fundamentals produce robust model tools for use in climate science. This is the science of ocean models: –Dynamical assumptions –Numerical methods –Physical parameterizations –Rational, complete, and pedagogical model documentation Well defined and fully documented experimental designs for model simulations are essential to realize robust results which can be reproduced by other groups. Absent the full documentation of model designs, one is doing irreproducible model integration (not science). This is the science of ocean modelling: –Forcing datasets –Bulk formulae –Restoring terms –Coupling methods –Integration times –Analysis methods

4. State-of-science for models and modelling Ocean models are not mature. Ocean modelling practice is not mature (i.e., global ocean-ice simulations are not generally comparable between groups). Methods used are often not robust, with ad hoc and undocumented steps employed to “get the models running.” This situation leads to modelling being as much an “art” as a science. That is, the simulations are often not reproducible (even by the group performing the original simulation!). Given the growing importance of ocean models for understanding and predicting global and regional climate, the models and the experimental design must be given a well documented scientific foundation.

5. WGOMD mission A central mission of WGOMD is to facilitate the maturation of ocean models, and the use of ocean models in well defined and reproducible ocean modelling simulations. WGOMD aims to realize this mission by providing pedogogical peer-review survey papers that document models and the experimental design of simulations. It also does so by organizing topical workshops that bring elements of the oceanography community together to discuss research and development areas relevant to increasing the scientific integrity of models and their simulations. Realizing this mission (or some aspect of it) allows WGOMD to provide scientifically based advice to other Clivar panels and to WGCM. This mission remains ongoing, with some success. However, further efforts are required to make routine use of ocean models by a scientifically literate researcher a process that produces useful scientific results.

6. Key contributions of WGOMD Review paper: Pedagogically documents state-of-art in ocean climate models (Griffies etal (2000)) Workshops: Topical workshops that facilitate collaboration, communication, and education –Princeton/GFDL 2004: State-of-art in Ocean Climate Modelling –Hobart/CSIRO 2005: Southern Ocean Modelling –Bergen 2007: Numerical Methods for Ocean Models CORE: Benchmark experiments for global ocean-ice models. Peer-review paper illustrates CORE-I with seven ocean-ice models each run for 500 years (Griffies etal in prep).

7. WGOMD review article (2000) Pedogogical survey of ocean climate model methods and parameterizations Highlighted vertical coordinates as key for model algorithms, with many complementary attributes between coordinates. Influenced AR4 ocean climate model developments. A basis for ongoing research efforts at improving model fundamentals.

8. Princeton/GFDL Workshop 2004: State of the art in ocean climate modelling Key developers of AR4 ocean climate models discussed their methods, parameterizations, and results. Experts in ocean physics and numerics scrutinized the AR4 models and made recommendations for next round of IPCC ocean models. Community input to the WGOMD’s efforts at establishing an OMIP. A key outcome was to propose CORE as a science-based collaborative project, rather than push forward with a mandatory OMIP, as such was was considered premature.

9. Hobart Workshop 2005: State of the art in Southern Ocean Modelling Southern Ocean is key to represent with high fidelity in climate models, as it represents a huge sink for heat and carbon, and the processes active have importance to all ocean basins. Science workshop discussed and debated methods of simulating and analyzing Southern Ocean physical and biogeochemical processes. Ten lectures with discussions provided pedagogical surveys of key aspects of the Southern Ocean.

10. Bergen Workshop 2007: Numerical Methods for Ocean Models Discuss and debate novel methods for developing the next generation of ocean models for global, regional and coastal applications. Bring together key practitioners and algorithm developers for eight provocative and pedagogical sessions. Enhance communication amongst a community of algorithm developers who typically do not have the opportunity to gather in such focused workshop settings.

11. Coordinated Ocean-ice Reference Experiments (COREs) Benchmark simulations for global ocean-ice models CORE-I proof of concept project includes seven model groups with three ocean model classes (geopotential, isopycnal, hybrid). A step toward an Ocean Model Intercomparison Project (OMIP)