Standard names: Propose new additions to the standard names table (Soil Moisture at different depths)

[YueLi92]

CMIP7 Land & Land Ice Data Request Author Team
Soil Moisture at different depths
Proposer's name: Yue Li
Date: Aug 20, 2024

Based on the recent scientific need to consider soil moisture at different layers, I'd like to propose standard names for soil moisture at the depths of 5cm, 10cm, 20cm, 50cm, and 100cm. The naming of these physical parameters follows the existing "mrso", whose CF Standard Name is mass_content_of_water_in_soil. The number of corresponding depths has been added to the end of the term.

The addition is based on my role as the co-lead of the CMIP7 Land and Land Ice Data Request Team and my discussion with Dr. David Lawrence (NSF NCAR). Several supporting scientific references are selected here: (DOI 10.1088/1748-9326/ac6f6d, doi.org/10.1016/j.rse.2021.112706, doi:10.5194/gmd-17-1869-2024).

Please find the proposed new standard names of soil moisture at different layers below. Thank you!

- Term Long Name Units

1. mrso5 mass_content_of_water_in_soil_5cm kg m-2
   Mean soil water content at a depth of 5 cm

2. mrso10 mass_content_of_water_in_soil_10cm kg m-2
   Mean soil water content at a depth of 10 cm

3. mrso20 mass_content_of_water_in_soil_20cm kg m-2
   Mean soil water content at a depth of 20 cm

4. mrso50 mass_content_of_water_in_soil_50cm kg m-2
   Mean soil water content at the depth of 50 cm

5. mrso100 mass_content_of_water_in_soil_100cm kg m-2
   Mean soil water content at the depth of 100 cm

[github-actions]

Thank you for your proposal. These terms will be added to the cfeditor (http://cfeditor.ceda.ac.uk/proposals/1) shortly. Your proposal will then be reviewed and commented on by the community and Standard Names moderator.

[taylor13]

I think the existing standard_name lwe_thickness_of_moisture_content_of_soil_layer should be satisfactory for this purpose. The generic units for this standard name are meters, not kg m-2, so an assumption would need to be made concerning the density of water.

[YueLi92]

Thanks. We will probably try to propose a variable based on this existing standard_name. But this multi-layer variable might be too big if the Data Request team wants a very high temporal frequency (e.g., 3hr) output. For example, a 3-hr output of soil moisture at only 5cm would be more feasible. If one variable containing all-layer soil moisture, the output might be too big regarding the size of the output. We need more discussion on this with the Land&Land Ice team.

[taylor13]

Hi @YueLi92. The "moisture content of soil layer" standard name can be used for variable limited to a single layer. I just noticed that there is another variable that is closer to your earlier suggestion: mass_content_of_water_in_soil_layer with units of kg m-2. Its description in the standard name glossary is:

  "Content" indicates a quantity per unit area. "Water" means water in all phases. "Layer" means any
 layer with upper and lower boundaries that have constant values in some vertical coordinate. There 
must be a vertical coordinate variable indicating the extent of the layer(s). If the layers are model
 layers, the vertical coordinate can be "model_level_number", but it is recommended to specify a 
physical coordinate (in a scalar or auxiliary coordinate variable) as well. Quantities defined for a soil 
layer must have a vertical coordinate variable with boundaries indicating the extent of the layer(s).

You need to define a vertical coordinate even in the case of a single layer and define its bounds. You can do this in a couple of different ways, but defining a "scalar" coordinate as described here is a good one. Please add a comment if further guidance is needed.

[github-actions]

This issue has had no activity in the last 30 days. Accordingly:

• If you proposed this issue or have contributed to the
  discussion, please reply to any outstanding concerns.
• If there has been little or no discussion, please comment
  on this issue, to assist with reaching a decision.
• If the proposal seems to have come to a consensus, please
  wait for the moderators to take the next steps towards
  acceptance.

Standard name moderators are also reminded to review @feggleton @japamment @efisher008

[japamment]

Hi @YueLi92

I agree with the suggestion made by @taylor13 on 21st August to use the existing standard name mass_content_of_water_in_soil_layer which has units of kg m-2.

This name would work whether you prefer to store the soil moisture for all layers in a single variable or split it between individual variables, one per layer. In either case you would need to specify an appropriate vertical coordinate (vector or scalar, respectively) to give the depth of the layer and provide coordinate bounds to define layer thickness.

Please add a comment in this issue if more information or examples are needed.

Best wishes
Alison

[efisher008]

Hi all @YueLi92 @japamment @taylor13,

As there has been no further discussion and the action (to use the existing standard name above) appears to be resolved, can this issue now be closed?

Best regards,
Ellie

[taylor13]

fine with me.

[YueLi92]

Thank you all for the help! Fine for me to close this as we decide to use the mrsol instead of proposing new variable name.

[japamment]

Thank you @YueLi92. I am closing this issue now because a new standard name is no longer required.