title: Key evidence of the role of desertification in protecting the underlying permafrost in the Qinghai-Tibet Plateau.
abstract: Previous research has shown that the temperature of underlying permafrost decreases after the ground surface is covered with sand. No significant conclusions have yet been drawn that explain why this happens, because the heat transfer mechanism effects of the sand layer on the underlying permafrost remain unclear. These mechanisms were studied in the present work. We found that the upward shortwave radiation flux of the Qinghai-Tibet Plateau ground surface with a sand layer covering was higher than that of the surface without sand; thus, the atmospheric heat reflected by the sand layer is greater than that reflected by the surface without sand. Therefore, the net radiation of the surface with the sand layer is lower than that of the surface without sand, which reduces the heat available to warm the sand layer. Because sand is both a porous medium and a weak pervious conductor with poor heat conductivity, less heat is conducted through the sand layer to the underground permafrost than in soil without the sand deposition layer. This phenomenon results in a decrease in the ground temperature of the permafrost under the sand layer, which plays a key role in protecting the permafrost.
authors.affiliation: Key Laboratory of Desert and Desertification/State Key Laboratory of Frozen Soil Engineering/Dunhuang Gobi and Desert Research Station, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou 730000, China.
authors.forename: Shengbo
authors.initials: S
authors.lastname: Xie
authors.affiliation: Key Laboratory of Desert and Desertification/State Key Laboratory of Frozen Soil Engineering/Dunhuang Gobi and Desert Research Station, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou 730000, China.
authors.forename: Jianjun
authors.initials: J
authors.lastname: Qu
authors.affiliation: Key Laboratory of Desert and Desertification/State Key Laboratory of Frozen Soil Engineering/Dunhuang Gobi and Desert Research Station, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou 730000, China.
authors.forename: Yuanming
authors.initials: Y
authors.lastname: Lai
authors.affiliation: Institute of Transportation, Inner Mongolia University, Hohhot 010070, China.
authors.forename: Xiangtian
authors.initials: X
authors.lastname: Xu
authors.affiliation: Institute of Desertification Studies, Chinese Academy of Forestry, Beijing 100091, China.
authors.forename: Yingjun
authors.initials: Y
authors.lastname: Pang