about Bottom Friction

[toaeh]

I am a student who has just started studying roms.
I have a question while running the model.
My model domain size is 3 km to 6 km. so the grid size is not the same.
If the floor areas of the two point grids are different within the same model domain and the roughness of bottom is same,
I thought that a larger bottom friction should be applied to the area where the area is larger.
However, looking at the source code below, it seems that the area of the bottom is not considered.


!-----------------------------------------------------------------------
! Set kinematic bottom momentum flux (m2/s2).
!-----------------------------------------------------------------------
!
! Set quadratic bottom stress.
!
DO j=Jstr,Jend
DO i=IstrU,Iend
cff1=0.25_r8*(v(i ,j ,1,nrhs)+ &
& v(i ,j+1,1,nrhs)+ &
& v(i-1,j ,1,nrhs)+ &
& v(i-1,j+1,1,nrhs))
cff2=SQRT(u(i,j,1,nrhs)*u(i,j,1,nrhs)+cff1*cff1)
bustr(i,j)=0.5_r8*(rdrag2(i-1,j)+rdrag2(i,j))* &
& u(i,j,1,nrhs)*cff2
END DO
END DO
DO j=JstrV,Jend
DO i=Istr,Iend
cff1=0.25_r8*(u(i ,j ,1,nrhs)+ &
& u(i+1,j ,1,nrhs)+ &
& u(i ,j-1,1,nrhs)+ &
& u(i+1,j-1,1,nrhs))
cff2=SQRT(cff1*cff1+v(i,j,1,nrhs)*v(i,j,1,nrhs))
bvstr(i,j)=0.5_r8*(rdrag2(i,j-1)+rdrag2(i,j))* &
& v(i,j,1,nrhs)*cff2
END DO
END DO


If the area is not considered in the ROMS as I think, I wonder if using the UV_DRAG_GRID option to increase the rdrg2 value in proportion to the area will help the model. (I am using the UV_QDRAG option.)
thank you

[jcwarner]

if you have a uniform current on a non-uniform grid, the stress would be uniform because the current is uniform.
the areas are taken into account when the time stepping of the full equations.
you can dig into the details here:
https://www.myroms.org/wiki/Documentation_Portal