Add default Ω_Earth and R_Earth for FPlane and BetaPlane

[ali-ramadhan]

Resolves #510

[glwagner]

How many significant digits would we like to use? The number of digits in each constant is not consistent.

[ali-ramadhan]

How many significant digits would we like to use? The number of digits in each constant is not consistent.

I think we should use as many significant digits as possible up to experimental uncertainty. Why should different constants have the same number of significant digits, especially if they're not always combined?

For Ω_Earth we have 7.2921150 ± 0.0000001 × 10^−5 radians per SI second so I updated this PR to use 7.292115e-5.

For R_Earth the Handbook of Chemistry and Physics quotes 6371.0 km for the mean radius of the Earth so I updated the PR to use 6371.0e3.

[glwagner]

I guess that's a fair point. I don't think we use all the significant digits available from experiments for g_Earth. Just thought it could be nice to make a decision so we don't end up making arbitrary truncations in cases where constants are known to 42 digits, but we decide not to copy 42 digits into the source code.

Right --- R_Earth is a bit ambiguous.

But if the values of such constants are super important to users simulations, its probably best to encourage them to set them explicitly in scripts.

But, hardly matters at this point since all we do are rectangles...

[ali-ramadhan]

Just thought it could be nice to make a decision so we don't end up making arbitrary truncations in cases where constants are known to 42 digits, but we decide not to copy 42 digits into the source code. Kind of happened with the gas constant: CliMA/ClimateMachine.jl#496

I think in these cases we should copy over all 42 digits.

But if the values of such constants are super important to users simulations, its probably best to encourage them to set them explicitly in scripts.

But, hardly matters at this point since all we do are rectangles...

True.

If it turns out to be a bad idea to assume defaults then we can take them away.

[codecov]

Codecov Report

Merging #550 into master will increase coverage by 3.86%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #550      +/-   ##
==========================================
+ Coverage   67.72%   71.59%   +3.86%     
==========================================
  Files          69       71       +2     
  Lines        1952     2341     +389     
==========================================
+ Hits         1322     1676     +354     
- Misses        630      665      +35

Impacted Files	Coverage Δ
src/coriolis.jl	60.86% <100%> (ø)	⬆️
src/boundary_conditions.jl	69.06% <0%> (-4.97%)	⬇️
src/halo_regions.jl	83.05% <0%> (-3.07%)	⬇️
src/TimeSteppers/kernels.jl	57.8% <0%> (-2.6%)	⬇️
src/AbstractOperations/computations.jl	75.75% <0%> (-0.25%)	⬇️
src/Solvers/batched_tridiagonal_solver.jl	100% <0%> (ø)
src/logger.jl	0% <0%> (ø)
src/Oceananigans.jl	76.92% <0%> (+1.92%)	⬆️
src/OutputWriters/netcdf_output_writer.jl	89.23% <0%> (+2.69%)	⬆️
src/utils.jl	74.35% <0%> (+2.79%)	⬆️
... and 8 more

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