How to denote when variables are located at cell tops

[cbegeman]

Right now, it is unclear without scrutinizing the code where variables like this one defined at the top of cell layers are located:

Omega/components/omega/src/ocn/Eos.cpp

Line 361 in ec8fe1c

"Brunt-Vaisala frequency squared", // Long Name

I can think of several options for making it clear where variables like this are defined in Omega:

1. Follow MPAS-Ocean and include Top (or Bot) in the variable name.
2. Add 'defined at layer tops' to the descriptions of variables such as this one. The main downside of this one is that users may fail to read the variable description.
3. Always use interface dimensions NVertLayersP1 for these variables and assign the bottom value to the fill value or 0.

I prefer Option 3. If you have a preference, please leave a comment!

[xylar]

I would strongly prefer Option 3. The dimension makes relatively clear where it lives. I prefer Inter over Top or Bot if any clarification is needed. And I agree that fields like Brunt-Vaisala frequency that don't have a sensible value at the seafloor could just have a fill value. (Brunt-Vaisala frequency would ideally also have a fill value at the sea surface since it can't be computed there either.)

[vanroekel]

I also much prefer option 3

[cbegeman]

Decision:

Go with Option 3
Always use interface dimensions NVertLayersP1 for variables that are defined on interfaces and assign a fill value for interfaces where the values are invalid (e.g., surface interface and seafloor interface for dX/dz variables).

Action items:

• Convert all existing variables that have dimensions NVertLayers but are defined at layer tops or bottoms to NVertLayersP1
• Create any new variables according to this schema