Daily And Seasonal Patterns Of Soil Temperature
The range of soil temperature in summer and winter decreases with increasing depth. At 40 cm depth the change is very minor and at 81 cm no diurnal change occurs.
In summer soil temperature decreases with depth during the day time.Temperature gradients direct heat into the soil. At night hours the temperature is highest between 20 and 40 cm, and from that level heat is directed both upward and downward.
In winter the 81 cm depth is warmer and the diurnal change is still very minor at 40 cm depth. Heat is transferred upward from those levels though out the day and night, because of the low radiation intensity in winter. The daily range of surface temperature is very small; however the range is still greater at the surface than any below level. Only during the hours near noon does heat penetrate into the soil from the surface.