Modeling the Evaporation Process

Mathematical methods for description of the processes of evaporation from the soil surface under conditions of the sub-arid zone of the south of Russia are discussed. Theoretical studies in this area and the results of their practical application have been analyzed. Natural observations are explained using mathematical modeling. Mathematical models of evaporation from the soil surface are divided into two types: physico-mathematical, which are based on the interaction between the water and the soil carcass, and phenomenological, which are based on balance ratios. The data on the evaporation from the surfaces of light soils have been analyzed with allowance for the diffusive and film transfer of moisture within the pore space. The cumulative evaporation from extended areas has been analyzed using a semi-empirical model, which connected evaporation intensity with the precipitation and the hydrophysical state of the soil moisture in the aeration zone. Good agreement between the theory of the capillary transfer of moisture and the data on the evaporation from the surface of open sandy soils has been revealed. A nonlinear relationship between the evaporation rate and the depth of the underlying surface, as well as the capillary-sorption pressure, has been revealed. The amount of annual precipitation in the south of Russia and the cumulative evaporation are associated with each other via a power dependence indicating the capillary-sorption nature of the evaporation.