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Eddy parameterization in the 1/10 deg resolution model

Model resolution as high as 1/10 deg is able to resolve ocean eddies. I wonder if any modification is made to the eddy-related parameterizations, or the parameterizations are completely turned off in this case?

Thanks!!
 

njn01

Member
The short answer is that out-of-the-box, the pop2 ocean model parameter settings are automatically selected so as to be an appropriate choice for the given resolution.  When you create and set up a new case, the CESM scripts will, behind the scenes, select suitable parameterizations for you, including eddy-related parameterizations. Presently, there are active parameterization studies being conducted with the 0.1-degree pop2 ocean model, and the results of these studies will be used to select the parameterizations provided in  the next CESM release. Included in the present investigations are a higher vertical resolution and internal mixing parameterizations.  Note that there is an adjustment period early in a 0.1-degree ocean startup, during which time you may need to adjust the ocean timestep size. The out-of-the-box value of dt_count = 500 may be a bit small (timestep too large); you may find you need to set dt_count = 750 or so for the first month, after which time you can reduce dt_count (increase the timestep) for the remainder of your experiment.
 
Thanks for the information. Right now I'm just analyzing the results of such a high resolutuion experiment. I was just wondering that, specifically in 0.1 deg resolution runs where mesoscale eddies are resolved, does CESM automatically turn off the parameterized mesoscale eddy mixing (e.g. Gent_McWilliam parameterization) used in non-eddy resolving configurations? Otherwise the model could double count the effect of mesoscale eddy mixing.  
 

njn01

Member
In the CESM POP2 ocean model,  more than one option for horizontal mixing exists, but in any given experiment, only one such option is selected.   That is, in your words, there is no "double-counting" of the mixing.By default in the 0.1-degree CESM POP2 ocean model, biharmonic horizontal mixing is applied to both tracer and momentum terms.
 
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