Submitted to: Methods of Soil Analysis
Publication Type: Book / Chapter
Publication Acceptance Date: December 9, 2000
Publication Date: November 1, 2002
Citation: SAUER, T.J. HEAT FLUX DENSITY. METHODS OF SOIL ANALYSIS. DANE, J.H., TOPP, G.C., EDITORS. SOIL SCIENCE SOCIETY OF AMERICA, MADISON, WI. PART 4 - PHYSICAL METHODS. 2002. P. 1233-1248.
Soil heat flux density (G) is the amount of energy transported through a unit area of soil per unit time. Although energy may be transferred by radiation and convection in very shallow soil layers, in most instances conduction is considered the principal mode of energy transport in soils. The measurement of G is of primary concern when characterizing the thermal regime of soil layers and with respect to the surface energy balance. Soil heat flux density typically represents only 1-5% of the net radiation on a daily basis although this percentage can increase to 50% in arid climates or during spring and fall when net radiation is low and the soil is warming/cooling. Four methods are routinely used for measuring G: 1) calorimetric, 2) gradient, 3) combination, and 4) soil heat flux plate. The background of each method is discussed followed by a discussion of the necessary equipment and procedural steps. Lastly, the advantages and limitations of each method are presented. The heat flux plate method has become the most popular method. Considerable attention is given to the potential sources of errors, correction for heat storage and latent heat transfer, and selection of plates with characteristics appropriate for the intended application.