Restrictions of soil evaporation

Independently of the choice of evaporation method, the estimated soil evaporation is limited to the fraction of snow free ground, for the calculation of the water balance of the uppermost soil layer. If condensation is predicted, the estimated (negative) soil evaporation is also restricted to a maximum rate, e_max,cond :

                               (4.31)

where f_bare is the fraction of bare soil. The soil evaporation is finally restricted to a limited portion of the soil water content of the upper most soil layer (arbitrarily chosen to 10%), to avoid negative soil moisture contents:

                                 (4.32)

The numerical restrictions on the mass flux of water have not yet been incorporated in the heat balance.