Heat Transfer in Soil

the process of heat flow between the soil surface and the deeper layers. Heat transfer is closely associated with heat conductivity, which results from differences in the temperature of various soil layers, and with the heating capacity of the soil. The flow of heat is directed from warmer layers to cooler layers—in summer toward the deeper layers and in winter toward the surface.

Heat transfer in soil is substantially influenced by the snow cover, vegetation, and terrain. For example, a deep snow cover significantly decreases heat loss from the soil because of its low heat conductivity. The rate of heat transfer depends essentially on the moistness of the soil. In dry soil the process of heat exchange is slow: the pores are filled with air, which has low heat conductivity, and heat is transferred through the points of contact of the soil particles. With an increase in moisture, heat conduction in the soil increases, and the rate of heat transfer rises. Diurnal variations are observed in heat transfer: during the day the heat flow is directed downward, and at night, up toward the surface. Layers of earth at depths of 10–20 m undergo annual heat transfer; layers at depths up to 100 cm undergo diurnal heat transfer.

Knowledge of heat transfer in soil and between the soil and the atmosphere is very important in developing measures for regulating soil temperature and for combating frost, drought, and dry winds.