An improved methodology to measure evaporation from bare soil based on comparison of surface temperature with a dry soil surface

• Published in: Journal of hydrology (Amsterdam) 1998-09, Vol.210 (1), p.93-105
• Main Authors: Qiu, Guo Yu, Yano, Tomohisa, Momii, Kazuro
• Format: Article
• Language: English
• Subjects: Air temperature; Bare soil; Dry soil surface temperature; Drying soil surface temperature; Earth sciences; Earth, ocean, space; equations; Exact sciences and technology; Measuring evaporation; soil temperature; Soils; Surficial geology
• ISSN: 0022-1694; 1879-2707
• DOI: 10.1016/S0022-1694(98)00174-7

Accurate estimation of the resistances to water vapor movement is a major difficulty in evaluating evaporation from soil. By including the temperature of a dry soil surface (the temperature of the surface of a dry soil column buried in the field), a method for estimating evaporation from soil is proposed. The necessary input variables for the suggested method are temperature, net radiation, and soil heat flux. There are three advantages of the proposed method over the conventional methods. First, soil surface resistance and aerodynamic resistance are not required. Second, the variables included are fewer. Third, measurement and analysis of the parameters involved are relatively easy. Sensitivity analysis shows that the suggested method is sensitive to temperatures. Test experiments were conducted in a sandy field, where a weighing lysimeter was installed. Evaporation from soil, together with the variables specified above, were measured. For temperatures measured by thermocouples, experimental results showed that the mean absolute error (MAE) for the daily evaporation over 22 days was 0.17 mm day1. The regression between calculated and measured evaporation was highly significant ( r 2 = 0.89). Moreover, the intercept and slope of the regression equation were not significantly different from zero and unity, respectively, at the 0.05 probability level. Furthermore, by using the temperatures measured by infrared thermometers, the MAE between measured evaporation and estimated evaporation was 0.15 mm day −1. The regression between them was highly significant ( r 2 = 0.94) In addition, the intercept and slope of the regression equation were not significantly different from zero and unity, respectively, at the 0.05 probability level. These results show that evaporation calculated using the proposed method is in good agreement with lysimeter measured values. By comparing with the temperature difference method, it was shown that the suggested method estimated soil evaporation more accurately than the temperature difference method. Therefore, it is concluded that the proposed method is not only a simple way for application, but also an accurate way to estimate soil evaporation.