Area is not set for NUOPC single point cases

[ekluzek]

Brief summary of bug

@swensosc and Meg Fowler report this. Area is set to missing value 1.e36 when running with SCAM and nuopc (so PTS_MODE with nuopc).

General bug information

CTSM version you are using: latest master

Does this bug cause significantly incorrect results in the model's science? No -- unless area is needed (such as hillslope model)

Configurations affected: PTS_MODE

Details of bug

area is read in for PTS_MODE in MCT from the surface dataset, but the new process for setting latitudes and longitudes in NUOPC seems to neglect area.

@mvertens I wanted to point this out to you. I don't think this should be hard to fix. We should be able to read it from the surface dataset in every case. But, if you have other thoughts on this feel free to add them.

[mvertens]

@erik - this was deliberate. For a single point area does not make sense and is arbitrary. We are not doing any mapping and in fact for single point ssp forcing data the edges of the single point are set to -90->90 and 0->360. You could get the area from the surface dataset - but why would you want to do this if you don't need it?

[swensosc]

gridcell area is used in the hillslope model. I'd prefer not to have special code for the single point case, so it would be nice to also have an area assigned for the single point case regardless.

On Tue, Jul 20, 2021 at 2:31 PM mvertens @.***> wrote:

@erik https://github.com/erik - this was deliberate. For a single point area does not make sense and is arbitrary. We are not doing any mapping and in fact for single point ssp forcing data the edges of the single point are set to -90->90 and 0->360. You could get the area from the surface dataset

• but why would you want to do this if you don't need it?

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[mvertens]

@swensosc - thanks for the clarification. So you mention having an area assigned. This area is variable depending on the model resolution. How would you get this area - and does it matter what its value is - or does it just have to have a value that is not 1.e36.

[ekluzek]

@mvertens we have always been careful to assign area in the surface datasets for single point cases. For PTS_MODE the area is just the area of the grid cell you are running at. But, for single point cases with a surface dataset you should just use the area from there. In PTSCLM we assigned a certain arbitrary grid size, but it was on the dataset.

[swensosc]

It will matter what the value is. For example, some of the single point simulations will correspond to a field site or catchment, and the area can be used to output a discharge (volume/time) to compare to observations.

On Tue, Jul 20, 2021 at 2:39 PM mvertens @.***> wrote:

@swensosc https://github.com/swensosc - thanks for the clarification. So you mention having an area assigned. This area is variable depending on the model resolution. How would you get this area - and does it matter what its value is - or does it just have to have a value that is not 1.e36.

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[mvertens]

@swensosc @erik - thanks for clarifying. I did not appreciate that. So Erik's proposed method should be able to handle getting the area.

[ekluzek]

@wwieder is area going to be important for NEON sites? I think the current process will use the area for the nearest point from the surface dataset that acts as parent to the extraction script. So it won't be a very good characterization of the actual area of the site as for example it will be a f09 grid cell. If area is going to be important for NEON we'll need to be able to assign it in some better fashion.

[wwieder]

I don't see this being critical for NEON simulations, as NEON data would be reported in a per area (or per volume) basis (e.g., soil C stocks).

[ekluzek]

@mvertens and @swensosc and I talked about this briefly among other issues. @mvertens thought that @jedwards4b should work on this. But, he's currently on vacation. But, after he gets back he should be able to do this part of the single point work he is doing with NEON.

[wwieder]

As above, I don't think area is important for the NEON simulations, but it's fine for @jedwards4b to work on this more broadly for single point cases.

[jedwards4b]

@ekluzek Please provide a particular compset and location which illustrates this issue.