关键词: 浅层包气带, 土体温度, 变温带, 滞后效应, 分布规律, 变化模式

Abstract: The earth temperature mainly depends on meteorological factors such as atmospheric temperature, solar radiation intensity, rainfall, and air humidity. Taking the hilly and gully region of the western Weihe River basin in the Loess Plateau as the research area, a field observation site was established. The response of ground temperature of the shallow zone of aeration in situ to climate change was monitored in real-time. Through field monitoring data and theoretical analysis, it is found that the distribution law and change mode of soil temperature are as follows: meteorological factors only affect the soil temperature in the variable temperature zone, with the atmospheric temperature and solar radiation intensity being the main influencing factors. The deeper the soil layer, the lesser the impact. The phase of soil temperature shifts linearly with the depth of the soil, which means that the soil temperature has a hysteresis effect with depth. Analysis shows that the phase of the temperature curve of the soil at a depth of 760cm is exactly opposite to that at the surface, where the temperature lags behind the surface for half a year. Monitoring data predicts that the depth of the constant temperature zone in this area is 1193cm with a temperature of 13.152℃. When calculating the theoretical lag time of the soil temperature, the thermal diffusivity of the soil is regarded as a constant. It will cause discrepancies between theoretical and observed values, with the difference diminishing with increasing soil depth.

Key words: the shallow vadose zone, soil temperature, the variable temperature zone, hysteresis effect, the distribution law, change mode