Following up from https://github.com/PecanProject/sipnet/pull/307/changes#r3030678232

The term "soil water content fraction" is overloaded in docs:

• In parameters.md, $W_{\text{soil}}$ is the notation used for soilWFracInit
• Equations use $\frac{W_{\text{soil}}}{W_{\text{WHC}}}$ for this same quantity
• $W_{\text{soil}}$ is used both as a quantity (cm) and unitless / normalized fraction

Solution

Use $f_{\text{WHC}}$ as for normalized soil water fraction

1. Update parameters.md

Initial conditions table

Replace:

$W_{\text{soil},0}$ ... 

With:

$f_{\text{WHC},0}$ ... soilWFracInit ... Initial soil water fraction ... unitless ... May exceed 1.0 when modeling flooded conditions; $W_{\text{soil},0} = f_{\text{WHC},0} \cdot W_{\text{WHC}}$

Soil Water Table

Add the following line to soil water content table

| $f_{\text{WHC}}$ | Soil water content as fraction of WHC | unitless; internally clipped to [0,1] in dependency functions, but can exceed 1 in flooded conditions |

Or, how should we handle the two different ways (clipped and unclipped) f_WHC is used?

Update rSoilConst1 and rSoilConst2 notes from:

soil resistance = e^(rSoilConst1 - rSoilConst2 * W1), where W1 = (water/soilWHC)

To:

soil resistance = e^(rSoilConst1 - rSoilConst2 * f_WHC)

3. Update model-structure.md — "Soil Water Content Fraction" section

Clarify that:

• $f_{\text{WHC}} = \frac{W_{\text{soil}}}{W_{\text{WHC}}}$ (unbounded)
• $f_{\text{WHC}^*}=\operatorname{clip}(f_{\text{WHC}}, 0, 1)$ or some appropriate notation
  • moisture dependency functions
  • evapotranspiration