Effect of temperature and water content on surface albedo of loess in cold regions and the associated mechanisms

Surface albedo, as one of the important properties of the underlying surface, has a significant impact on the surface energy balance in cold regions. However, due to the complexity of the factors affecting surface albedo, existing calculations still contain inaccuracies. Therefore, this study conducted surface albedo experiments on loess with different water contents and temperatures. By analyzing the surface albedo measurements of samples with varying temperature and water content levels, as well as the soil freezing characteristic curve (SFCC) and soil-water characteristic curve (SWCC) of loess, the study explores the influence of soil temperature and water content on the surface albedo of loess. The results indicate that both the temperature and water content of loess jointly affect surface albedo. During the process of albedo change, there exists a water content threshold that alters the trend of surface albedo. Soil temperature influences surface albedo by affecting the content of pore ice and liquid water within the soil. When the water content of loess is relatively low, the surface albedo decreases as the unfrozen water content decreases. However, this trend changes as the water content of loess increases. Additionally, a decrease in soil temperature lowers the moisture content threshold during the changes in surface albedo. This study provides a reference for exploring and determining the surface energy balance in cold regions under the background of warm and humid climates, as well as for establishing thermal calculation boundaries.