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(*) Vorticity and divergence are not required if U and V are provided (and viceversa)
* Comment from MeteoFrance (Constantin Ardilouze) about soil moisture
I am quite aware of this issue since I have recently worked on a multi-model comparison involving the soil moisture component. In our view, only the root zone soil moisture is relevant since the deeper soil moisture is not directly available for evapotransiration.
We suggest that everybody provides the Soil Wetness Index (SWI) of the root zone which is computed as SWI=(WaterContent(root)-WiltingPoint(root))/(FieldCapacity(root)-WiltingPoint(root)). SWI does allow inter-model comparison. We can provide "SWI" as well as the "root zone depth" (in m) and the "root zone water content" (in m3/m3). However, we cannot provide the wilting point and field capacity of the root zone, because this root zone is composed of a variable number of soil layers, each of them having its own wilting point and field capacity.
In addition to SWI, root zone depth and root zone water content, we can also provide - if you decide so - the total soil water content (in m3/m3 or in kg/m2) + total soil depth (both must come together). But again, these two fields seem less relevant to us because they do not tell much about the soil water that can potentially affect the climate through evapotranspiration.