Experimental evaluation and parameterization of evaporation from soil surface

Surface evaporation is one of the main processes in the soil–atmosphere interaction. Since it is highly related to meteorological factors and soil properties, determination of evaporation rate from soil surface remains a challenge. To investigate the evaporation from unsaturated soil, a climate control apparatus has been newly developed, which has a feature of completely controlling air temperature, relative humidity and wind speed. Twelve climatic conditions are applied to three kinds of soil specimens to carry out the evaporation tests. The results show that only water content cannot allow an accurate estimation, additional variables accounting for soil texture and wind speed must be included as well. Moreover, a simple approach to parameterize evaporation is presented by the soil moisture θ of top 1-cm layer with considering the effect of soil texture and wind speed. It is found that the new approach is able to accurately estimate the evaporation from unsaturated soil.