Seasonal variations in the thermal diffusivity of the surface rocks and the effect of moisture

Rock weathering is a fundamental aspect of Earth's evolutionary processes. The surface rock constitutes a critical zone that interacts with solar and water. However, there has been a lack of data to quantify the transient effects of these interactions. In this study, we employ thermal diffusivity ($\alpha$) at a macroscopic scale to investigate the transient thermal response mechanisms, utilizing temperature data collected at multiple depths. The results show that the thermal diffusivity values exhibit seasonal variations, with different trends in winter and summer, and the variation amplitudes show differences at different depths. We analyzed and discussed the mechanism and believe that the cause of the seasonal variation of thermal diffusivity is the change of moisture in the surface rocks and the phase change of water-ice. This study helps to deepen the understanding of the weathering process of surface rocks and its correlation with climate change. At the same time, it provides new insights for application fields such as engineering geology and stone conservation that are concerned about the weathering of surface rocks.