[MITgcm-support] balance OBCS correction

[钱钰坤]

Hi all,


I've known that the balance OBCS can overwrite the flows given at OBs to ensure a zero-mass transport.  In a regional run, is the model-output flow at OBs the original (unbalanced) OBCS or corrected (balanced) OBCS?  I really want to know how large does such correction affect my simulation.


I wonder if there could be a further improvement for the balance OBCS.  The current balance OBCS does correction every time step so that the seasonal variation of sea level cannot be reproduced even the original OBCS contains such signal.  Generally, a regional run with a climatological forcing (annual cycle) will produce net inflow in some season/month and net outflow in the remaining, but the sum over the year will be zero.  I hope to use a balance OBCS can automatically balance the flow during the period of the climatological forcing.


While there seems no such option, I decided to correct the net flow myself.  After reading obcs_balance_flow.F, I found that in computing the east OB tileArea, maskInW (2D array) is used instead of maskW (3D array) (see lines 149-153 in obcs_balance_flow.F for version c65m).  The area is for east OB is in vertical-meridional plane so it is strange not to use a vertically varying (3D) mask, as there are less ocean grids in the deeper ocean.  It is appreciated if someone could tell me the difference between maskInW and maskW (I only know that maskInW is the interior mask for u point, from the comments in GRID.h).


Thanks in advanced.

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