[MITgcm-support] GMRedi parameterization

[钱钰坤]

Hi all,


I'm not sure about the best combination of diffusivities defined between data and data.gmredi files.


For climate simulation, in z-coordinate model (such as MITgcm), diffusion should be primarily along isopycnal rather than horizontal.  Therefore, I guess diffusivities defined in data file (e.g., diffKh and diffKr) should be set to zero to prevent spurious diapycnal mixing.


GMRedi package is used in MITgcm to diffuse tracer in local isopycnal coordinates through some kind of rotation.  However, I cannot find definitions of isopycnal and diapycnal diffusivities in data.gmredi file.  In the test case of tutorial_global_oce_latlon, there is a GM_isopycK, which is commented, that may be isopycnal diffusivity but no diapycnal definitions (or even a ratio between them).  There is also a GM_background_K in data.gmredi which I don't understand why we need it.


Besides, does the GMRedi scheme apply to the viscosities for momentum?


GM sheme is proposed to parameterize effects of geostrophic eddies in non-eddy resolving model.  If the model is eddy resolving, do we still need to include this scheme?



------------------
 Best regards 
 
Yu-Kun Qian (钱钰坤) 
Center for Monsoon and Environment Research 
 Department of Atmospheric Sciences
School of Environmental Science and Engineering 
 Sun Yat-sen University 
No. 135 Xingang West Road, Haizhu District 
Guangzhou, 510275, P.R. China 
Tel; 020-84115227 
Email: qianyk at mail3.sysu.edu.cn
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