Seventh Conference on Coastal Atmospheric and Oceanic Prediction and Processes


Developing a simple 2D ocean model for the evaluation of the MM5 results over Bodega Bay

Adam Kochanski, DRI, Reno, NV; and D. Koracin and C. E. Dorman

The wind stress, generated by a wind blowing above the ocean surface, and the wind stress curl are crucial to generating ocean circulation. However, the available measurement data have serious limitations. The buoy data show only a part of the meteorological situation at certain locations and don't provide sufficient information about the spatial distribution of the wind speed. Therefore, a computation of the wind stress curl pattern, which is extremely important in generation of the upwelling, can not be performed based only on the buoy data. The satellite data, on the other hand, provide a spatial picture of the wind speed, but their sparse resolution and the lack of valid data close to the shore limits their application to the ocean simulation in coastal areas. Because of that, the Fifth-Generation NCAR / Penn State Mesoscale Model (MM5) seems to be a good alternative data source that could be used for forcing the ocean models, if it provides accurate results in coastal areas. Hence, the main goal of this work is to check how the MM5 model performs in the coastal area of Bodega Bay and if its results can be used for forcing ocean models. The validation of the atmospheric data over the ocean is a difficult task because of the lack of spatially distributed measurement data of sufficient resolution. In this study we focus on the evaluation of the modeled wind stress and the wind stress curl. For the former, we use available buoy wind speed data that we compare with MM5 simulation. For the latter one, we employ more sophisticated methods. First of all, we compute the wind stress curl based on measurements from three closely located buoys moored in Bodega Bay, and then compare it with the wind stress curl computed from the model data. There are several schemes that can be used for the wind stress curl computation from the data from the set of three buoys, and each of them provides different results. Because of this arbitrariness we perform an additional analysis. Since we want to evaluate the applicability of the MM5 data to ocean models forcing, we perform an additional test. We develop a reduced-gravity 2D ocean model that serves as a tool for evaluation of the basic effect of the atmospheric field on the ocean circulation. The simplicity of this model helps to control the most important ocean parameters and to minimize the effect of model initialization and parameterizations in terms of basic results. We link this model with the atmospheric model, and simulate the ocean current pattern induced by the simulated MM5 wind field. We are mostly interested in the application of the simulated wind field for simulation of the upwelling and relaxation events. Therefore, in our analysis we focus on the simulation of relaxation and upwelling events observed during the first half of July 2001. Finally, we validate the results from the two-dimensional ocean model forced by the MM5 wind field via comparison with the ocean currents measurements from Bodega Bay field program, as determined by the high frequency radar (CODAR).

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Poster Session P1, 7Coastal Posters
Monday, 10 September 2007, 6:00 PM-8:00 PM, Macaw/Cockatoo

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