Contents of /MITgcm/pkg/obcs/README

Using NonLin-FrSurf with OBCs:
 
In addition to values of uVel,vVel, T and S at the OB, you need to
specify also the values of eta at the OB (done in S/R OBCS_CALC).
 
The OB-eta values are primary defined at the boundaries (u point
for E/W  OBC ; v point for N/S OBC) and not at the cell center.
They are directly used to compute hFacW and hFacS at the boundaries
(no space average or min/max). This enable us to control exactly
the inflow / outflow at the OB (i.e. the product hFacW*uVel or hFacS*vVel).
 
The same OB-eta values are also applied to the etaH field (cell center
next to the boundaries) to update consistently hFacZ (e.g.: used in
horizontal viscous term). This secondary "obc_apply" has no effect
on volume and tracer flux through the OB.
 
NB: Orlanski radiative OBC not yet implemented for NonLin-FrSurf terms. 
1	Using NonLin-FrSurf with OBCs:
2
3	In addition to values of uVel,vVel, T and S at the OB, you need to
4	specify also the values of eta at the OB (done in S/R OBCS_CALC).
5
6	The OB-eta values are primary defined at the boundaries (u point
7	for E/W OBC ; v point for N/S OBC) and not at the cell center.
8	They are directly used to compute hFacW and hFacS at the boundaries
9	(no space average or min/max). This enable us to control exactly
10	the inflow / outflow at the OB (i.e. the product hFacWuVel or hFacSvVel).
11
12	The same OB-eta values are also applied to the etaH field (cell center
13	next to the boundaries) to update consistently hFacZ (e.g.: used in
14	horizontal viscous term). This secondary "obc_apply" has no effect
15	on volume and tracer flux through the OB.
16
17	NB: Orlanski radiative OBC not yet implemented for NonLin-FrSurf terms.