`IntialVertCoord` stream name and `InitVertCoord` field group are confusing.

[andrewdnolan]

From some offline discussion with @xylar the IntialVertCoord stream is in fact not an initial condition file (as implied by Initial), but contains time independent fields related to the VertCoord that always need to be read in OnStartUp.

Omega/components/omega/configs/Default.yml

Lines 109 to 118 in 6d2ddfc

	InitialVertCoord:
	UsePointerFile: false
	Filename: OmegaMesh.nc
	Mode: read
	Precision: double
	Freq: 1
	FreqUnits: OnStartup
	UseStartEnd: false
	Contents:
	- InitVertCoord

We should rename this stream to match the naming convention HorzMeshIn, which makes it clear that it's always an input and therefore time independent. So a new stream name of VertCoordIn and a field group name of VertCoordIn. Additionally adding a comment the Default.yml explaining that stream is time independent will help avoid future confusion.

[xylar]

Another option could be to remove this stream and keep all vertical coordinate fields in the state. There is already a confusing split between the time-dependent (e.g. SurfacePressure, PseudoThickness) and the time-independent (e.g. minLayerCell, maxLayerCell, GeomBottomDepth). It is plausible that minLayerCell and maxLayerCell could be made time-dependent with future vertical coordinates.

Perhaps this separate stream is not actually useful?

[cbegeman]

Given that the IO stream attributes (besides Contents) are the same as InitialState, it seems that most of the organizational benefit is coming from the InitVertCoord field group. So I would be comfortable removing this stream and adding InitVertCoord to the contents of InitialState.