pressure gradient in the diagnostic output

[winterbellgirl]

Hi,

Is there any way to separate the barotropic and baroclinic pressure gradient in the 2D diagnostic output? There is only one term (ubar_prsgrd/vbar_prsgrd) in the diagnostic output. I learned that this term contains both the barotropic and baroclinic parts.

I found where the baroclinic pressure gradient is computed in the model. In my case I defined 'DJ_GRADPS', so the baroclinic pressure gradient is computed in prsgrd32.h, but I didn't find out where the barotropic pressure gradient is computed. I think it should be computed from the sea level gradient, but still I want to know its computation location. Could anybody give me some instructions? Thanks!

[crowley]

Most of the work calculating the 2D diagnostics happens in step2d_LF_AM3.h. I believe the forcing terms for the coupling are computed (at least in part) in rhs3d.F.

[LiuZHQ]

How about just calculate the barotropic PGF from the standard zeta output? I think it is better than changing the ROMS codes.
you can get baroclinic PGF by subtracting barotropic PGF from total PGF.

[rduran]

I dont think THE baroclinic pressure gradient(bpg) is included in a vertically averaged pressure gradient. It would need to have vertical dependence to be THE bpg. Rather there is a term of baroclinic nature included in the uv_bar_prsgrd terms to make the barotropic-baroclinic coupling work.

[winterbellgirl]

How about just calculate the barotropic PGF from the standard zeta output? I think it is better than changing the ROMS codes.
you can get baroclinic PGF by subtracting barotropic PGF from total PGF.

Thank you for your reply. Actually I did the opposite recently. I computed the baroclinic pressure gradient, and subtracted it from the total pressure gradient (3D). The resulting pattern is a barotropic one, but it is not the one I computed from the surface elevation gradient. Rather it resembles the pattern of the total pressure gradient at the bottom, while the one computed from zeta gradient resembles the pattern at the surface. Still, I did not really find where the barotropic pressure gradient is computed in ROMS.