[MITgcm-support] stagger grid and obcs

[钱钰坤]

Dear MITgcm user,


Although I've asked related questions about stagger grids here, I am still a little confused about them.


Here let's make a concrete example in x direction only.  Assume that there are 3 zonal grids (Nx=3), then the zonal velocity points and mass points are laid out as:
      u1        c1        u2        c2        u3        c3        u4


When OBCS is off, periodic OB is used so that u1=u4.  In this case, we only need to prepare 3 zonal velocity values and 3 tracer values for u(1-3) and c(1-3).


When OBCS is on, OBwU is applied to u1 and u2 (Martin told me this is very important) and OBeU is similarly applied to u3 and u4.  Then the effective values of u is only 2 (Nx-1), which means that the one column of initial u field (Nx=3) will be overwritten by OBu.  I'm a little confused whether the outer most of initial velocity fields should be exactly the same as those of OBs?  If yes, then the effective velocity in the model interior should be Nx-1 and the output velocity field should contain at least one slice of OB velocity.  If true, which OB should be output? East or west?


Can anyone clarify these details?  Thanks in advance.

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