Hydrothermal conditions of southern and northern slope soils of northeastern Great Xing'an Mountain, China

The purpose of the article is to study the influence features of polar-oriented slopes on the near-surface energy and hydrothermal balance in the seasonal cryolithozone. The authors carried out a complex of field observations including measurement of air and underlying surface temperature, soil moisture, solar radiation and wind speed at the hydrological stations of Songling (southern slope) and Luoguhe (northern slope) in the northeast of the Great Xing'an Mountain (China). The analysis of the data obtained allowed to conclude that, on the one hand, the long-term influence of the thermal balance components causes significant differences in the soil structure and properties on differently oriented slopes. The number of daily freeze-thaw soil cycles on the southern slope (100 cycles) significantly exceeds the ones on the northern slope (56 cycles). The soil on the southern soil is 3 °C warmer than that on the northern slope, and its humidity in the area of the Songling hydrological station is lower than that at the Luoguhe station. On the other hand, differences in soil properties control the energy exchange between the atmosphere and the earth's surface, this means that the incoming short-wave solar radiation and heat flux into the soil on the southern slope is greater than on the northern one. Therefore, slope orientation is one of the significant environmental factors affecting the influx of solar energy, temperature and humidity of the soils in the northeastern Great Xing'an Mountain. It also has a decisive role for the spatial distribution and evolution of seasonal permafrost in the region and, accordingly, affects the stability and safety of engineering structures. The performed research is important for understanding the relationship between climate and frozen soil in the mountainous areas with seasonal cryolithozone as well as for optimization of boundary conditions when modeling rock freeze-thaw processes.