[MITgcm-support] obcs with staggered grid

[Weifeng (Gordon) Zhang]

Hi,

I am a little puzzled by the way mitgcm handles the open boundary 
conditions.

In obcs_cal.F, OBWu, OBWv, OBWw, OBWt, and OBWs are specified. Are these 
variables at the same grid locations (the model does the 
interpolation/extroplation internally), or they are at their own 
staggered grid locations with half-grid offsets?

If the variables are at the staggered grid locations, how come they have 
the same size in all directions? Shouldn't there be a size offset of 1 
in some of the variables, for instance, OBWv's size in y being greater 
than the y-size of the other variables by 1, and OBWw's vertical size 
being greater than the other variables by 1?

For OBWw, because it is 0 on the bottom interface, the bottom OBWw is 
neglected? What about OBWv then, how is it handled on the north and 
south boundaries?

Thanks,

Gordon