Topsoil Moisture Evaluator in Surface Mesh Visualization Files (Feature Request)

[saubhagya-gatech]

Similar to the water table evaluator, it would be beneficial to have a topsoil moisture evaluator that computes the average soil moisture content for a specified number of upper layers and stores it on the surface mesh. With transpiration and water table depth already available in surface visualization files, this addition would reduce the need to frequently save subsurface files, as surface files would contain most of the key hydrological quantities.

The top 5 cm of soil is particularly valuable for model evaluations, especially for comparisons with field data or satellite products like SMAP and SMAP-HydroBlock.

[ecoon]

Please add an equation, and list out any parameters/flags/options you expect this would accept. Include units.

[saubhagya-gatech]

The soil moisture content of the topsoil, θ (in percentage), can be calculated as:

θ = (100 / D) ∫[0 to D] φ(z) * S(z) dz

where:

• φ(z) is the porosity as a function of depth z,
• S(z) is the saturation index as a function of depth z,
• D is the total depth over which the integration is performed.

Parameters:

• dependency keys for saturation and porosity field
• number of layers - this will be layers at the top of the domain for which average is taken.

[ecoon]

Rather than number of layers, this should probably be provided as D, the depth [m]. I'd rather not assume a fixed layer structure.

Do you really want it in percentage, and not just [-] (e.g. in [0,1]) ? I'm not sure if we have anything else in % in ATS, but porosity, saturation, etc are all in [-].

[saubhagya-gatech]

yes, [-] is good, need not to be percentage. Sure, we can provide depth. So, perhaps consider layers whole bottlom elevation is higher than the D? This quanity is more meaninful for D from 50-100 cm. I guess we can leave this judgement to user.

[ecoon]

We can interpolate if D is inconsistent. I mean, if you ask for D = 5 cm, but your dzs [cm] are { 2, 2, 2, ...}, then, assuming piecewise constant saturations, it's WC_0 + WC_1 + WC_2 / 2.

[saubhagya-gatech]

right, I was more worried about thick layers below top soil if some gives too high D value. Interpolation should be fine. By the way, we can also just directly use water content divided by volume, either equation is fine.