[MITgcm-devel] vectorization of layers

[Ryan Abernathey]

Martin,

Thanks so much for your work to improve this. I am traveling at the moment
and have not been able to try out the code. I will be back on my office on
thursday and can try it out then. It certainly *looks* fine. If you are
convinced it is working well, I would go ahead and check it in.

Regarding the "mean depth", what I always do is to use the thickness
variables to reconstruct the mean depth. For example, Hs gives the mean
layer thickness at the v points. You just cumsum it up to give the layer
boundary depths and then find the midpoints for the mean depths. This would
only not work is when the water column is not stably stratified with
respect for the tracer. For my purposes, this doesn't happen, but it would
definitely happen with, for example, salinity. However, in this case, the
mean depth of a tracer layer itself is poorly defined. What if there are
two salinity maxima with the value of 35 psu at very different depths? Does
it make sense to talk about mean depth of the 35 psu surface? So I guess my
point is that I don't think it makes sense to add another variable for the
mean depth.

I definitely think we are at the point where we need a more robust
verification experiment.

-Ryan




On Tue, Jan 8, 2013 at 9:54 AM, Martin Losch <Martin.Losch at awi.de> wrote:

> Hi Ryan,
>
> did you get a chance to look at the changed layers_fluxcalc.F?
> I also tried to further the vectorization and I did succeed technically,
> but at the cost of nearly infinite execution time, so even if my idea gives
> the correct results, there is no computational gain (although nicely
> vectorized). I feel that, what we have now (what I sent with my last
> email), is the best I can do right now. I am happy to check that in, if you
> approve of it.
>
> I have a general question. Does it make sense to compute (and save) the
> "mean depth" of the layers? I would need that to compute, e.g. the
> overturning stream function averaged on isopycnals but plotted as a
> function of latitude and depth. Reconstructing the depths after the run
> does work, but it becomes a little noisy (as does the post-mortem
> computation of the overtuning on density surface, that's why your layers
> package is so useful).
>
> Martin
>
>
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