- #1
rc_nmt
- 6
- 0
I am running a general circulation model (EPIC, which uses isentropic vertical coordinate system, potential temperature) and need to add vertical diffusion to the zonal velocity U. The vertical coordinate is theta (Θ, potential temperature) and there is no vertical height coordinate in z but I need to find ∂2U / ∂z2.
I solve for ∂U / ∂z by using the relation ∂Θ / ∂z = N*Θ / g. So then I can use the chain rule and use finite difference approximations to solve for ∂U / ∂z = ∂U / ∂Θ * ∂Θ / ∂z which is also equal to ∂U / ∂z = ∂U / ∂Θ * N*Θ / g. This equation works correctly for the first derivative of U with respect to z.
The problem I am facing now is another derivative of this expression which gives me ∂ / ∂z [
∂U / ∂Θ * N*Θ / g ] . So what I would like to know is, is there some symmetry property of second derivatives I can use here? How can I solve this without creating a vertical coordinate in z and just use Θ as I did for the first derivative in ∂U / ∂z? Is it possible? How if I apply the product rule does the first term work out to have no z dependence and be valid?
Thank you to who ever can assist me.
Cheers
Rick
I solve for ∂U / ∂z by using the relation ∂Θ / ∂z = N*Θ / g. So then I can use the chain rule and use finite difference approximations to solve for ∂U / ∂z = ∂U / ∂Θ * ∂Θ / ∂z which is also equal to ∂U / ∂z = ∂U / ∂Θ * N*Θ / g. This equation works correctly for the first derivative of U with respect to z.
The problem I am facing now is another derivative of this expression which gives me ∂ / ∂z [
∂U / ∂Θ * N*Θ / g ] . So what I would like to know is, is there some symmetry property of second derivatives I can use here? How can I solve this without creating a vertical coordinate in z and just use Θ as I did for the first derivative in ∂U / ∂z? Is it possible? How if I apply the product rule does the first term work out to have no z dependence and be valid?
Thank you to who ever can assist me.
Cheers
Rick
Last edited by a moderator: