On the heat flow into the ground

Two expressions have been developed to predict the periodic variation of the ground temperature with depth. They are based on the energy balance equation at the ground surface and the assumption that the temperature variation at the ground surface is in the form of a sine-wave or a Fourier series. The energy balance equation involves the periodic variation of solar radiation, atmospheric temperature and the latent heat flux due to evaporation. The heat flux into the ground has been derived and the damping depth and the corresponding ground temperature have been calculated. A parametric study showed that the ground temperature and the amplitude of the heat flux into the ground increase with the increasing in the air relative humidity and the ground absorptivity. Conversely, they decrease with the increasing in the evaporation fraction and wind speed. The values of the damping depth is almost the same while the corresponding ground temperature is influenced by the various parameters significantly.

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