Abstract
The soil heat flux is an important component of heat exchange across the ground surface and is an es-sential input component used to help quantify evapotran-spiration ratio based on the heat budget. Consequently, it is useful to understand the characteristics of soil heat flux measurement methods. One objective of the current study was to compare the temperature gradient method with the heat flux plate method at a depth of 0.02 m. A second ob-jective was to assess the effect of heat storage in the soil surface layer (0.02 m thickness) under different soil water conditions. Further, the effect of the Philip’s correction on the measurement of the heat flux plate method was also as-sessed. The results indicate that the soil heat flux measured by the heat flux plate method was almost identical with the heat flux measured by the temperature gradient method when the soil thermal conductivity was approximately half of the conductivity of the heat flux plate (i.e., wet condi-tion). In contrast, the heat flux plate method overestimated the absolute value of the soil heat flux with a constant ra-tio when the soil thermal conductivity was approximately 1/10 of the conductivity of the heat flux plate (i.e., dry con-dition). In addition, the practical effect of the Philip’s cor-rection was not observed. Further, the heat storage in the surface layer showed a diurnal variation with a range com-parable to the variation of the soil heat flux at a depth of 0.02 m, whereas the net daily heat storage was quite small.
