Evaluation of Methods for Determining the Apparent Thermal Diffusivity of Soil Near the Surface

Abstract

Field‐measured values of soil temperature were used to calculate the apparent thermal diffusivity of the upper 10 cm of soil with six different methods. The limitations of the six methods were analyzed both in terms of the calculated results, and for the quantity and quality of data required to make the calculations. Four of the six methods, Amplitude, Phase, Arctangent, and Logarithm, provided explicit equations for the thermal diffusivity. These explicit methods required only a few measurements of temperature, and calculations were simple to perform; however, the results were found to be erratic and in general inconsistent with known or more reliable estimates of the apparent thermal diffusivity. Two methods, Numerical and Harmonic, which made use of larger numbers of temperature measurements to implicitly solve for the apparent thermal diffusivity, generally provided more reliable estimates. Calculated values of the apparent thermal diffusivity by both methods were used in predicting soil temperature for comparison with measured temperature. Even under partly cloudy conditions both methods predicted temperatures very well. In general the data requirement of the Numerical method was 12 to 24 measures of temperature per day at three depths, while the Harmonic method only required 8 to 12 measures of temperature per day at two depths.

Soil profile method for soil thermal diffusivity, conductivity and heat flux: Comparison to soil heat flux plates

“…Horton et al [2] developed a measurement method for a based on harmonic analysis. The method entailed fitting a Fourier series to the diel (24-hour) soil temperature measured at 1-h intervals at 0.01-m depth followed by the prediction of temperatures at a depth, z (0.1 m), based on the Fourier series solution to the onedimensional heat flux problem using an assumed a value.…”

Soil thermal diffusivity estimated from data of soil temperature and single soil component properties

“…Thermal diffusivity can be estimated under field conditions from soil temperature data (Carslaw & Jaeger, 1959;Kirkham & Powers, 1972). Theory and experimental considerations to determine soil thermal diffusivity from measured temperatures are clearly exposed by Horton et al (1983). Corresponding experimental results have been reported by many authors (Adams et al, 1976;Prevedello, 1993;Ramana Rao et al, 2005;Passerat de Silans et al, 2006;Gao et al, 2007) Alternatively, thermal diffusivity can also be estimated from the properties of single soil components (solids, water and air) together with their spatial organization.…”

“…There are several mathematically independent ways of doing so (Horton et al, 1983). The first method employs two temperature amplitudes (A 1 and A 2 , K or °C) measured during the same time intervalusually corresponding to one wave period at two depths (z 1 and z 2 ).…”

“…A third method was proposed by Seemann (1979) and quoted (with modifications) by Horton et al (1983). It is based on four temperature observations during a 24 h period (6 h between observations), at two depths.…”

Determinação in Loco da difusividade térmica num solo da região de Caatinga (PB)

“…Segundo a literatura (De Vries, 1963;Horton et al, 1983;Passerat de Silans et al, 1996), vários métodos têm sido utilizados com o objetivo de quantificar a difusividade térmica e, para tanto, utilizam dados de temperatura do solo em diferentes profundidades. Neste trabalho, os métodos harmônico (HM), da Transformada de Laplace corrigido (CLTM) e de Nassar e Horton (NHS) são utilizados e descritos a seguir.…”