[MITgcm-support] passive tracer restoring

[钱钰坤]

Hi all,


I've released a passive tracer q in a specific setup and let the tracer evolve under the dynamic flows without any sources.


Due to the numerical diffusion induced by advection schemes (no explicit diffusion is set), the tracer variances decay slowly with time.  Therefore, for a long-time run, the global averaged tracer variance (or overall gradient estimated roughly by qmax-qmin) will decrease all the time.  To prevent this, I need the restoring method by Alen and Nakamura (2003, JAS):


q*=-1+2(q-qmin)/(qmax-qmin)


After this restoring (and normalization) at each time step, the tracer maximum and minimum values will remain between -1 and 1, and do not decay with time.


The problem is where to add this restoring code (or which source file to add to) every time step, so that it is a simple and easy task.


I've thought to use RBCS but RBCS seems to suitable for prescribed tracer field and the restoring formula here is tracer dependent.


Thanks in advance.


Reference:
Allen, D. R. and N. Nakamura, 2003: Tracer Equivalent Latitude: A Diagnostic Tool for Isentropic Transport Studies. J. Atmos. Sci., 60, 287-304.



------------------
 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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