MODELING WORKGROUP

We discussed cooperation both within the modeling group and with other groups. Our goal is to create a linked hydrodynamic-sediment transport-biological model. The foundation of that model will be an existed Great Lakes version of the Princeton Ocean Model. Ice transport, sediment transport and biological models will be built as extentions of the existing code. This approach will allow us to not only develop independently new modules, but will also make it possible to shut off these modules for specific modeling activities in the future. We will add an option to use a different advection scheme to the existing central difference scheme which is known to produce excessive diffusion in areas of large spatial gradients. We will start with using 2 km rectangular bathymetric grid. We will consider the possibility of either using 1 km or finer horizontal resolution in the future, or using curvilinear orthogonal or non-orthogonal grids, or using the nested grid approach. Having a one year simulation as a goal, in the beginning of the program we will be running seasonal simulations only with the hydrodynamic model. Other models will be run only for selected episodes during 1992-97 and program field years. For these episodes we will also be experimenting with fine resolution (6 and 3 km) meteorological fields provided by the meteorological model MM5. The model will be run for that purpose in the hindcast mode with re-initialization every 12 hr. We also discussed how modeling can help in planning Lagrangian measurements, and shipboard surveys. In particular, adding Lake Michigan to the Great Lakes Forecasting System at OSU by 1998 will be useful in providing timing and spatial gradients for cruise planning.

Currently, the hydrodynamic model is running experimentally on the 5 km grid, providing nowcasts and 36 hr forecasts every 6 hours. The 2-dimensional sediment transport model will be added to the system by 1998. In addition, Paul Roebber suggested the idea to issue a 'plume alert' warning aproximately 5 days in advance based on the propagation of major atmospheric systems into the area of interest. We will also be trying to develop estimates of resuspension potential based on the wave model results. Modeling can also help interpret observations by doing process studies and scenario testing. To fill gaps in observations, we will be using data assimilation techniques. We are planning to have a graduate student working exclusively on that problem. Finally, we started a discussion on how obtained Great Lakes experience can be transfered to other aquatic systems. In particular, we discussed the possibility of existence of nearshore-offshore transport similar to the two-gyre circulation transport in the East and West U.S. Coast environment. Studies of sensitivity of circulation to small-scale atmospheric variability will be important for coastal hydrodynamics in general. Another important novelty will be process studies with the linked sediment transport-biological model.

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