2:2.3.3 Sublimation and Evaporation from the Soil

The amount of sublimation and soil evaporation will be impacted by the degree of shading. The maximum amount of sublimation/soil evaporation on a given day is calculated as:

$E_s=E'_o*cov_{sol}$ 2:2.3.7

where $E_s$ is the maximum sublimation/soil evaporation on a given day (mm H$_2$O), $E'_o$ is the potential evapotranspiration adjusted for evaporation of free water in the canopy (mm H$_2$O), and $cov_{sol}$ is the soil cover index. The soil cover index is calculated

$cov_{sol}=exp(-5.0*10^{-5}*CV)$ 2:2.3.8

where $CV$ is the aboveground biomass and residue (kg ha$^{-1}$). If the snow water content is greater than 0.5 mm H$_2$O, the soil cover index is set to 0.5.

The maximum amount of sublimation/soil evaporation is reduced during periods of high plant water use with the relationship:

$E'_s=min[E_s,\frac{E_s*E'_o}{E_s+E_t}]$ 2:2.3.9

where $E'_s$is the maximum sublimation/soil evaporation adjusted for plant water use on a given day (mm H$_2$O), $E_s$ is the maximum sublimation/soil evaporation on a given day (mm H$_2$O), $E'_o$is the potential evapotranspiration adjusted for evaporation of free water in the canopy (mm H$_2$O), and $E_t$ is the transpiration on a given day (mm H$_2$O). When $E_t$ is low $E'_s \rightarrow E_s$. However, as $E_t$ approaches , $E'_o$,$E'_s\rightarrow\frac{E_s}{1+cov_{sol}}$ .