A comparative analysis of transpiration and bare soil evaporation

Transpiration E^sup v^ and bare soil evaporation E^sup b^ processes are comparatively analysed assuming homogeneous and inhomogeneous areal distributions of volumetric soil moisture content ϑ. For a homogeneous areal distribution of ϑ we use a deterministic model, while for inhomogeneous distributions a statistical-deterministic diagnostic surface energy balance model is applied. The areal variations of ϑ are simulated by Monte-Carlo runs assuming normal distributions of ϑ. The numerical experiments are performed for loam. In the experiments we used different parameterizations for vegetation and bare soil surface resistances and strong atmospheric forcing. According to the results theE^sup v^(ϑ)-^sup E^b(ϑ) differences are great, especially in dry conditions. In spite of this, the available energy flux curves of vegetation A^sup v^(ϑ) and bare soil A^sup b^(ϑ) surfaces differ much less than the E^sup v^(ϑ) and ^sup E^b(ϑ) curves. The results suggest that E^sup v^ is much more non-linearly related to environmental conditions than ^sup E^b. Both E^sup v^ and ^sup E^b depend on the distribution of ϑ, the wetness regime and the parameterization used. With the parameterizations, ^sup E^b showed greater variations than E^sup v^. These results are valid when there are no advective effects or mesoscale circulation patterns and the stratification is unstable.[PUBLICATION ABSTRACT]