[mpas-developers] Changes to Constants

[Doug Jacobsen]

Hi Developers,

I ran into an issue the other day and thought I might let everyone know so
they could avoid having to find it. As some of you may know, Todd and I have
been trying to reproduce some of his JCP papers results using MPAS. We had
success a little while back (using revision 120 of the code), and were
trying to explore the same things using a higher order advection scheme.
Working in revision 263 of the code I was unable to reproduce the results,
so I spent almost all of yesterday trying to figure out why.

It appears that somewhere between these two revisions the values for the
radius of the earth and the rotation of the earth were modified. We have
been using Williamson Shallow water test cases (and their respective
reference solutions), and these use a specific value for a and omega. Here
are the definitions of each a and omega for the different revisions. I'm not
sure when they were changed, as I didn't go through all of the revisions to
find it, but it was somewhere in the last 143 revisions. Hopefully this
helps someone who runs into a problem reproducing results made previously.
It's easy for me to just modify the framework/module_constants.F file, so I
don't know if I need to commit this change back, but it might be useful to
know the difference.

Revision 120:
a       = 6371220.0
omega   = 7.292e-5

Revision 263:
a       = 6371229.0
omega   = 7.29212e-5

Williamson:
a = 6.37122e6
omega = 7.292e-5

Doug
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