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Session: |
Renewable Energy and Earth Systems II |
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Title: |
Ocean Modeling for Climate: From Eddy-Permitting to Eddy-Resolving |
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Chair: |
Bill Buzbee (Buzbee Enterprises) |
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Time: |
Wednesday, November 19, 10:30AM - 11:15AM |
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Rm #: |
16-18 |
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Speaker(s)/Author(s): |
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Frank Bryan (Climate and Global Dynamics Division, National Center for Atmospheric Research) |
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Description: |
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Frank O. Bryan, Climate and Global Dynamics Division, National Center for Atmospheric Research; Norikazu Nakashiki and Yoshikatsu Yoshida, Environmental Sciences Department, Abiko Research Laboratory, Central Research Institue of Electric Power Inustry
As a consequence of the difference in the stratification of the ocean as compared to the atmosphere, the dominant scale of eddies, or "weather" in the ocean is 10-100 times smaller than that in the atmosphere. For climate applications, where global models of each fluid are required, this implies that the ocean component would require up to approximately a factor of 1 million more computational points (100 in each horizontal dimension and 100 in time) to achieve "dynamically equivalent resolution" as the atmosphere model. The complexity of the geometry of the ocean domain boundary and the presence of boundary layers on all bounding surfaces also put high demands on the resolution requirements in ocean modeling. This situation has led to two distinct lines of ocean model development over the last few decades. On the one hand, coarse resolution models with relatively comprehensive representations of forcing and thermodynamic processes, but in which the effects of eddies have been parameterized, have been used in studies of the global climate system. In this class of models the horizontal resolution has improved from 300-500 km during the 1980's to approximately 50-100 km today. On the other hand, ocean modeling directed at understanding the eddies and their interaction with the time mean flow has been carried out with resolutions in the range of 5-25 km, but has required compromises in the completeness of the forcing and physics represented or the size of the domain or period of simulation, relative to those used in global climate studies. Today we are witnessing a convergence of these two streams of research. Coupled climate simulations with ocean components with resolutions in the range of 25-50km (referred to as "eddy-permitting") are currently underway by several groups, and multi-decade global ocean-only simulations with resolutions under 10 km ("eddy-resolving") have been completed. Computational facilities such as the Earth Simulator open the possibility for multi-decade to century time scale coupled climate system simulations in which the eddies of both the atmosphere and ocean are resolved. We will review the formulation of, and present results from experiments conducted on the Earth Simulator with an uncoupled global ocean model with a horizontal resolution of 0.1 degree to illustrate the range of ocean processes involved in the climate system. |
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Link: |
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