[MITgcm-support] passive tracer restoring

[Martin Losch]

Hi,

did you get an answer? 

You could modify the RBCS package to do what you want to do, but maybe simpler to edit ptracers_apply_forcing.F, where you can add any passive tracer tendency. You need to reformulate your method so that translates into a tendency (tracerunits/time) and add it to gPtracer in an extra loop. This routine is called for every vertical level (k), so a 2D loop sufficies:

        DO j=jMin,jMax
         DO i=iMin,iMax
          gPtracer(i,j) = gPtracer(i,j) + yourTendency(i,j)
         ENDDO
        ENDDO

Martin

> On 7. Jul 2017, at 05:25, 钱钰坤 <qianyk at mail3.sysu.edu.cn> wrote:
> 
> 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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