Experimental study of evaporation from soil-atmosphere interfaces

Experimental evaporation tests on 2–20 mm soil samples were performed under a wide range of atmospheric conditions using a climatic chamber. The relatively thin thickness of the samples was intended to represent the soil-atmosphere interface layer. Atmospheric conditions of wind velocity, air temperature, relative humidity and irradiance were imposed on bare soil surfaces of sand, compacted clay and kaolin slurry. The results of an extensive number of experimental tests show a good correlation between the atmospheric conditions measured near the soil surface and Potential Evaporation (PE) and soil initial evaporation rates. An empirical model based on an inverse sigmoid function is proposed to express the ratio between Actual Evaporation (AE) and Potential Evaporation (AE/PE) rates versus soil suction. The evaporation results of the present study may be used to predict PE and AE rates from soil surfaces of different textures under a broad range of environmental conditions. The empirical model may be used in soil-atmosphere interaction models to estimate water flux across soil-atmosphere boundaries.