Effects of Seasonal Snow Cover on Hydrothermal Conditions of the Active Layer in the Northeastern Qinghai-Tibet Plateau

Abstract. Snow cover significantly influences the moisture and thermal properties of the active layer in permafrost regions. Seasonal snow cover, soil temperature, and moisture were monitored in the northeastern Qinghai-Tibet Plateau (QTP) from December 2012 to February 2015. According to field data, the following conclusions were drawn. (1) The snow season in this region is predominantly during spring (March to May) and autumn (September to November), the thickness of individual snowfall events is usually less than 5 cm, and the duration of land surface snow cover is generally no longer than 5 days. (2) Removal of seasonal snow cover is beneficial for cooling the active layer in a whole year and in other seasons with the exception of summer. Further analysis on the ground temperature in the active layer shows that the cooling effect of the snow removal maybe results from the high thermal resistivity of snow, the delay of snowfall time in autumn, and the drastic decrease of moisture content in the active layer. (3) Seasonal snow cover maintains the high water content of the active layer. Snow removal can therefore lead to a rapid decrease of soil moisture content. A small decrease in water content of the active layer at the natural snow site (NSS) is related with less rainfall during the monitoring period. Significant differences between the NSS and the snow removal site (SRS) may depend predominantly on the inhibitory action of snow cover on the evaporation capacity of surface soil because of its cooling and shading effects during the daytime and in summer.