Abstract
Soil thermal parameters are mainly inputs for models of soil heat flux. Mathematical models are important tool for predicting the soil heat and water transfer, depending on some fundamentals of soil physical properties. Soil moisture is one of the soil physical properties that have a great effect on thermal parameters. The aim of the work is to describe the behavior of soil thermal parameters under different values of soil moisture, and is to investigate the effect of some fundamentals of soil physical properties on thermal parameters. We could describe the relationship between thermal diffusivity and soil moisture by ∩ shaped curve using a quadratic equation and evaluate the efficiency of this equation, statistically. Experimental thermal diffusivity (Kexp) by direct method and mathematical models were measured. Mathematical models were Chung and Horton model (1987) (Kcal-2), the model of Arkhangel’skaya (2004) (Kcal-3) and the suggested quadratic equation (Kcal-1). Efficiency of the quadratic equation and mathematical models were estimated using the correlation coefficient (R2), Root Mean Square Error (RMSE), and the Nash-Sutcliffe Efficiency (NSE). The values of R2, RMSR and NSE for the quadratic equation were 0.978, 0.24 and 0.95, respectively, for sod-podzolic soil under the study. The quadratic equation is a simple and faster equation for forecasting soil thermal diffusivity. Key words: Soil thermal parameters, thermal diffusivity, thermal conductivity, soil heat capacity, soil moisture, soil bulk density, organic matter, quadratic equation and mathematical models.
Highlights
Soil thermal parameters are playing an important role in many, chemical, biological, physical and environmental processes such as the dew, soil aeration, crop growth (Timlin et al, 2002), soil CO2 production (Buchner et al, 2008; Bauer et al, 2012), ecosystem carbon sequestration (Ju et al, 2006), and subsurface soil water evaporation (Sakai et al, 2011)
The soil heat transport simulations are based on estimates of the soil thermal conductivity and soil thermal diffusivity as a function of the soil water content
Soil physical properties are soil moisture, soil bulk density, particle size distribution and organic matter, which have a great effect on thermal parameters
Summary
Soil thermal parameters are playing an important role in many, chemical, biological, physical and environmental processes such as the dew, soil aeration, crop growth (Timlin et al, 2002), soil CO2 production (Buchner et al, 2008; Bauer et al, 2012), ecosystem carbon sequestration (Ju et al, 2006), and subsurface soil water evaporation (Sakai et al, 2011). The soil heat transport simulations are based on estimates of the soil thermal conductivity and soil thermal diffusivity as a function of the soil water content. On the other hand, (Tikhonravova and Khitrov, 2003) suggested a polynomial equation to estimate soil thermal diffusivity as a function of soil moisture as: K=K0+a1θ+a2θ2+a3θ5 where K0, a1, a2 and a3 are the parameters of the equation. (Arkhangel’skaya, 2004) proposed another kind of equation a lognormal equation dependence on thermal diffusivity from water content. (Arkhangel’skaya et al, 2015) described the relationship between thermal diffusivity and water content by Sshaped curve. The vertical one dimensional flux density of heat (JH (W m-2)) in soil is given by Fourier's la, q =- λ dT dZ where λ is soil thermal conductivity (J m-1 s-1 oC-1), T is temperature in oC and z is soil depth. λ could be considered as the apparent soil thermal conductivity, as latent heat transfer cannot be separated from conduction in moist soils
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