The heat flux density in a non-homogeneous bare loessial soil

This work describes the relationship between the diurnal patterns of the radiant energy exchange in the atmospheric surface layer and the soil heat flux density of a bare irrigated soil in an arid environment. The measurements show that the soil heat flux density is a large fraction of the net radiation. The soil moisture content has little effect on this fraction but modifies the phase relationship between the net radiation and the soil heat flux density waves. Differences between the thermal regimes of the wet and dry soil appear to be caused by latent heat exchanges rather than changes of the soil thermal properties. The data also show that the variation with depth of the soil thermal properties strongly influences the propagation of the temperature and heat flux density waves in the soil. A heat diffusion theory for non-homogeneous conductors (Lettau, 1962) which enables the thermal properties of the soil to be predicted is tested by comparison with experimental determinations in the field.