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Vertical velocity estimates and ALE remapping #1112
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The implementation of this diagnostic online is non-trivial because the calculation of |
I have no solution, but more questions to ask.
@StephenGriffies you're referring to the vertical remapping tendency for a tracer
and @hmkhatri and @StephenGriffies are wondering what an analogous term is for an implied vertical velocity. I almost feel like this is a broader question about how to transform between the vertical momentum equation in the Leclair and Madec flavor of ALE, vs. the regrid/remap flavor. My gut reaction is that it will be hard to define this transformation because of the vertically non-local nature of the regrid, remap operation. For example. Let's say that you went from the situation The velocity of an interface can be calculated as the difference in its position pre and post ALE, but I don't know how you would define the velocity across the interface let alone its acceleration. @hmkhatri @StephenGriffies , what are your thoughts on what the accelerations would be in this case? |
N to M layer remapping is implemented in the code by using max(N,M)+1 interfaces and implies abs(N-M) vanished layers in one or the other. |
The question wasn't necessarily about the N-M mappings, but more about the vertical velocities that's implied by the vanishing of the bottom layers. w velocity of the second interface is |
Deep down in the algorithm the remapping calculates the change in interface position, which is your w*time step. That's why we need that same number of interfaces in both pictures and represent a change in degrees of freedom with vanished layers. The particular solution for your setup is w(1)=0, w(2)=2, w(3)=1, w(4)=0 which takes your 3 cells of thickness 1 and produces h(1)=3, h(2)=h(3)=0. |
Gotcha, thanks for clarifying. You're referring to the |
So hypothetically, this is already there (without the division by Delta T): |
Yes, and the tendency due to remapping for scalars is https://github.com/NOAA-GFDL/MOM6/blob/2179c8813e21811006f96fade03850a8ad09faf1/src/ALE/MOM_ALE.F90#L838-L855, but a few lines down there is no similar diagnostic for the components of momentum. |
I guess it's kind of redundant to have the |
Yes, a diagnostic needs to be added as mentioned in https://github.com/NOAA-GFDL/MOM6/issues/1112#issuecomment-643488958 |
@hmkhatri please give see if you can write the diagnostic and see if it makes sense. This is encouraging. |
We are looking into the layer-wise momentum budget in MOM6 in z* coordinate. All terms in the momentum budget are available as diagnostics in MOM6 except the dia-surface velocity acceleration term. Is it possible to compute this term online in the remapping step?
Following the same, can we estimate vertical velocity online and output as a diagnostic in MOM6?
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