考虑降雨作用的气温升高对多年冻土活动层水热影响机制
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摘要
近50 a青藏高原暖湿化趋势显著,水热边界条件的改变必然影响多年冻土的稳定性和高原生态环境的演变。已有研究主要关注气候升温对冻土温度场的影响,而对升温过程伴随的活动层水分变化研究较少。基于土壤-地表-大气水分和能量平衡的冻土水-汽-热耦合模型,以青藏高原北麓河地区2013年实测气象资料为模型驱动数据,研究在降雨不变,气温不变、气温升高1℃和升高2℃情况下活动层水热响应机制与过程。结果表明:气候升温通过改变地表能量与水分平衡过程和土壤内部水热运移分量影响多年冻土水热过程。气温升高引起地表净辐射、蒸发潜热和土壤热通量增大,而地表降雨入渗和感热通量减少;气温升高会降低土壤含水率和土壤导水系数,但温度梯度及与温度梯度相关的水分和能量分量相应增大,而与水势梯度相关的水分和能量分量相对减少;升温对土壤温度场的影响比水分场明显,影响范围也更深;随着气温升高,地表蒸发量和活动层厚度增大,气温升高加速了冻土的退化过程,与降雨增加对冻土的热稳定性影响相反。
There is an obvious trend of climate warming and wetting on the Qinghai-Tibet Plateau during the past fifty years. Climate changes in air temperature or precipitation will inevitably influence the stability of permafrost. Previous studies mainly focus on the thermal influence of climate warming, but little is known about the induced rainfall infiltration and the hydrothermal response mechanism. Based on the meteorological data observed at Beiluhe observation station during 2013, the established water-vapor-heat transport model is used to predict the response under 1℃ and 2 ℃ increment of temperature, which considering the influences of rainfall. Climate change influences the thermal-moisture of permafrost mainly by changing the surface energy budget and soil hydrothermal transport components. The results show that climate warming greatly increased the surface net radiation, latent heat of evaporation and soil heat flux, decreased the sensible heat and rainfall infiltration. The rising air temperature reduces the soil moisture and soil hydraulic conductivity. Temperature gradient increases dramatically with temperature arising, further increases the moisture and energy components and reduces the components related to the water potential gradient. Climate warming increases the surface evaporation and thickness of active layer and accelerates the degradation of permafrost, which is contrary to the thermal effects of rainfall increasing.
There is an obvious trend of climate warming and wetting on the Qinghai-Tibet Plateau during the past fifty years. Climate changes in air temperature or precipitation will inevitably influence the stability of permafrost. Previous studies mainly focus on the thermal influence of climate warming, but little is known about the induced rainfall infiltration and the hydrothermal response mechanism. Based on the meteorological data observed at Beiluhe observation station during 2013, the established water-vapor-heat transport model is used to predict the response under 1℃ and 2 ℃ increment of temperature, which considering the influences of rainfall. Climate change influences the thermal-moisture of permafrost mainly by changing the surface energy budget and soil hydrothermal transport components. The results show that climate warming greatly increased the surface net radiation, latent heat of evaporation and soil heat flux, decreased the sensible heat and rainfall infiltration. The rising air temperature reduces the soil moisture and soil hydraulic conductivity. Temperature gradient increases dramatically with temperature arising, further increases the moisture and energy components and reduces the components related to the water potential gradient. Climate warming increases the surface evaporation and thickness of active layer and accelerates the degradation of permafrost, which is contrary to the thermal effects of rainfall increasing.
引文
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[26]宋二祥,罗爽,孔郁斐,等.路基土体“锅盖效应”的数值模拟分析[J].岩土力学,2017,38(6):1781-1788.SONG Er-xiang,LUO Shuang,KONG Yu-fei,et al.Simulation and analysis of pot-cover effect on moisture transport in subgrade soil[J].Rock and Soil Mechanics,2017,38(6):1781-1788.
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[28]张明礼,温智,薛珂,等.降水对北麓河地区多年冻土活动层水热影响分析[J].干旱区资源与环境,2016,30(4):159-164.ZHANG Ming-li,WEN Zhi,XUE Ke,et al.The effects of precipitation on thermal-moisture dynamics of active layer at Beiluhe permafrost region[J].Journal of Arid Land Resources and Environment,2016,30(4):159-164.
[2]OLIVA M,PEREIRA P,ANTONIADES D.The environmental consequences of permafrost degradation in a changing climate[J].Science of the Total Environment,2018,616-617:435-437.
[3]李韧,赵林,丁永建,等.青藏公路沿线多年冻土区活动层动态变化及区域差异特征[J].科学通报,2012,57(30):2864-2871.LI Ren,ZHAO Lin,DING Yong-jian,et al.Temporal and spatial variations of the active layer along the QinghaiTibet highway in a permafrost region[J].Chinese Science Bulletin,2012,57(30):2864-2871.
[4]SCHUUR E A,MCGUIRE A D,SCH?DEL C,et al.Climate change and the permafrost carbon feedback[J].Nature,2015,520(7546):171-179.
[5]LEHMANNKONERA S,FRANCZAK L,KOCIUBA W,et al.Comparison of hydrochemistry and organic compound transport in two non-glaciated high Arctic catchments with a permafrost regime(Bellsund Fjord,Spitsbergen)[J].Science of the Total Environment,2017,613-614:1037-1047.
[6]徐学祖,王家澄,张立新.冻土物理学[M].北京:科学出版社,2010.XU Xue-zu,WANG Jia-cheng,ZHANG Li-xin.Frozen soil physics[M].Beijing:Science Press,2010.
[7]周秀骥,赵平,陈军明,等.青藏高原热力作用对北半球气候影响的研究[J].中国科学(D辑:地球科学),2009,39(11):1473-1486.ZHOU Xiu-ji,ZHAO Ping,CHEN Jun-ming,et al.Impacts of thermodynamic processes over the Tibetan Plateau on the Northern Hemispheric climate[J].Science China(Series D-Earth Sciences),2009,52(11):1679-1693.
[8]CHANG J,WANG G X,LI C J,et al.Seasonal dynamics of suprapermafrost groundwater and its response to the freeing-thawing processes of soil in the permafrost region of Qinghai-Tibet Plateau[J].Science China(Series D-Earth Sciences),2015,45(4):481-493.
[9]韩熠哲,马伟强,王炳赟,等.青藏高原近30年降水变化特征分析[J].高原气象,2017,36(6):1477-1486.HAN Yi-zhe,MA Wei-qiang,WANG Bing-yun,et al.Climatic characteristics of rainfall change over the Qinghai-Tibetan Plateau from 1980 to 2013[J].Plateau Meteorology,2017,36(6):1477-1486.
[10]张人禾,苏凤阁,江志红,等.青藏高原21世纪气候和环境变化预估研究进展[J].科学通报,2015,60(32):3036-3047.ZHANG Ren-he,SU Feng-ge,JIANG Zhi-hong,et al.An overview of projected climate and environmental changes across the Tibetan Plateau in the 21st century[J].Chinese Science Bulletin,2015,60:3036-3047.
[11]WU Q,ZHANG T.Changes in active layer thickness over the Qinghai-Tibetan Plateau from 1995 to 2007[J].Journal of Geophysical Research Atmospheres,2010,115(D9):D09107.doi:10.1029/2009JD012974.
[12]CHENG G,JIN H.Permafrost and groundwater on the Qinghai-Tibet Plateau and in northeast China[J].Hydrogeology Journal,2013,21(1):5-23.
[13]WEN Z,ZHANG,M L,MA W,et al.Thermal-moisture dynamics of embankments with asphalt pavement in permafrost regions of central Tibetan Plateau[J].European Journal of Environmental and Civil Engineering,2015,19(4):387-399.
[14]ZHANG Z,WU Q,GAO S,et al.Response of the soil hydrothermal process to difference underlying conditions in the Beiluhe permafrost region[J].Environmental Earth Sciences,2017,76(5):194.
[15]WU Q B,HOU Y D,YUN H B,et al.Changes in active-layer thickness and near-surface permafrost between 2002 and 2012 in alpine ecosystems,QinghaiXizang(Tibet)Plateau,China[J].Global and Planetary Change,2015,124:149-155.
[16]张明礼,温智,董建华,等.多年冻土活动层浅层包气带水-汽-热耦合运移规律[J].岩土力学,2018,39(2):561-570.ZHANG Ming-li,WEN Zhi,DONG Jian-hua,et al.Coupled water-vapor-heat transport in the shallow unsaturated zone of active layer in permafrost regions[J].Rock and Soil Mechanics,2018,39(2):561-570.
[17]LI X,CHENG G.A GIS-aided response model of high-altitude permafrost to global change[J].Science in China(Series D-Earth Sciences),1999,42(1):72-79.
[18]NAN Z T,LI S X,CHENG G D.Prediction of permafrost distribution on the Qinghai-Tibet Plateau in the next 50and 100 years[J].Science China(Series D-Earth Sciences),2005,48(6):797-804.
[19]GUO D,WANG H,LI D.A projection of permafrost degradation on the Tibetan Plateau during the 21st century[J].Journal of Geophysical Research Atmospheres,2012,117(D5):D05106.
[20]ZHANG S,TENG J,HE Z,et al.Importance of vapor flow in unsaturated freezing soil:a numerical study[J].Cold Regions Science&Technology,2016,126(6):1-9.
[21]AN N,HEMMATI S,CUI Y.Numerical analysis of soil volumetric water content and temperature variations in an embankment due to soil-atmosphere interaction[J].Computers&Geotechnics,2017,83:40-51.
[22]吴紫汪,程国栋,朱林楠,等.冻土路基工程[M].兰州:兰州大学出版社,1988.WU Zi-wang,CHENG Guo-dong,ZHU Lin-nan,et al.Permafrost subgrade engineering[M].Lanzhou:Lanzhou University,1988.
[23]ZHANG M L,WEN Z,XUE K,et al.A coupled model for liquid water,water vapor and heat transport of saturated-unsaturated soil in cold regions:model formulation and verification[J].Environmental Earth Sciences,2016,75(8):1-19.
[24]CUI Y J,AN N T,HEMMATI S,et al.Experimental and numerical investigation of soil-atmosphere interaction[J].Engineering Geology,2013,165(15):20-28.
[25]张明礼,温智,董建华,等.降雨增加对多年冻土区铁路路基水热影响研究[J].岩石力学与工程学报,2017,36(10):2580-2590.ZHANG Ming-li,WEN Zhi,DONG Jian-hua,et al.The influence of rainfall increasing on thermal-moisture dynamics of railway embankment in cold regions[J].Chinese Journal of Rock Mechanics and Engineering,2017,36(10):2580-2590.
[26]宋二祥,罗爽,孔郁斐,等.路基土体“锅盖效应”的数值模拟分析[J].岩土力学,2017,38(6):1781-1788.SONG Er-xiang,LUO Shuang,KONG Yu-fei,et al.Simulation and analysis of pot-cover effect on moisture transport in subgrade soil[J].Rock and Soil Mechanics,2017,38(6):1781-1788.
[27]BANIMAHD S A,ZAND-PARSA S.Simulation of evaporation,coupled liquid water,water vapor and heat transport through the soil medium[J].Agricultural Water Management,2013,130:168-177.
[28]张明礼,温智,薛珂,等.降水对北麓河地区多年冻土活动层水热影响分析[J].干旱区资源与环境,2016,30(4):159-164.ZHANG Ming-li,WEN Zhi,XUE Ke,et al.The effects of precipitation on thermal-moisture dynamics of active layer at Beiluhe permafrost region[J].Journal of Arid Land Resources and Environment,2016,30(4):159-164.