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answer to question about orbital parameter bounds checks in astronomy.F90 comment #1627

@japhir

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@japhir

to answer the question in the comment in astronomy.F90
QUESTION : ARE THESE THE RIGHT LIMITS ???

I am not sure if the limits should be based on the physically possible values, or on the values for Earth specifically.

Earth's orbital eccentricity has varied between 0 and 0.067 for the past 100 Myr, so maybe a test more like 0 to 0.1 would be more suited?

Earth's obliquity has varied from 22° to 24.5° in the same time period, so a better range to check would be something like 10° to 40°? A negative value would not make sense, I think. It should be between 0° and 180°. EDIT: should be -90 to +90.

Earth's longitude of perihelion with respect to the moving equinox rotates and librates, so it does vary between 0° and 360°.

I could implement these changes in this pull request if desired.

These are the equivalent lines in shr_orb_mod.F90:
https://github.com/ESCOMP/CDEPS/blob/8197f05ef2549d3c53e4050c9821a683e2728bab/share/shr_orb_mod.F90#L27-L33

Describe the solution you'd like
Change the testing limits. Either to the theoretically valid ranges (i.e. change obliquity to 0 to 180) or to narrower ranges for Earth's orbital history.

Describe alternatives you've considered
Don't change it because the current wider ranges encompass the true ranges.

Additional context
I created this unrelated pull request that describes the issue there, before noticing that that was a fork of this repository.

ESCOMP#4

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