Freezing–thawing indices serve as a comprehensive indicator of both the duration of the freezing/thawing periods and the degree of cold and heat in a given region.In-depth analysis of the freezing-thawing indices not...Freezing–thawing indices serve as a comprehensive indicator of both the duration of the freezing/thawing periods and the degree of cold and heat in a given region.In-depth analysis of the freezing-thawing indices not only enables the prediction of permafrost distribution and its dynamic changes,but also facilitates the assessment of damage risk to infrastructure under freeze-thaw action.In this paper,the air/ground freezing–thawing indices from 1987 to 2017,based on daily temperature observations from meteorological stations along the China–Nepal Highway(CNH),were calculated,and their spatial and temporal variation patterns were analyzed.The results showed that:(1)Both mean annual air temperature and mean annual ground surface temperature along the CNH fluctuated upward,with climate tendency rates of 0.43 and 0.52.C·(10a)~(-1),respectively;(2)The number of days with negative air temperature and ground temperature showed fluctuated downward,with change rates of-8.6 and-8.3 d·(10a)~(-1),respectively;(3)The ranges of air freezing index,air thawing index,ground freezing index,and ground thawing index over the years were 157.05-458.88°C·d,2034.20-2560.73°C·d,108.78-396.83°C·d,and 3515.25-4288.67°C·d,respectively.The climate tendency rates were-5.42,10.22,-6.79,and 12.14.C·d·a-1,respectively,showing a general warming trend;(4)The air freezing index,ground freezing index,and ground thawing index changed abruptly in 1999,2000,and 2002,respectively,evincing significant changes after 2002.The research results can provide a basis for the risk assessment of freezing–thawing erosion and the prevention and control of permafrost engineering diseases along the CNH.展开更多
Against the background of global warming, environmental and ecological problems caused by frozen ground degradation have become a focus of attention for the scientific community. As the temperature rises, the permafro...Against the background of global warming, environmental and ecological problems caused by frozen ground degradation have become a focus of attention for the scientific community. As the temperature rises, the permafrost is degrading significantly in the frozen ground region of northeast China(FGRN China). At present, research on FGRN China is based mainly on data from meteorological stations, and the research period has been short.In this study, we analyzed spatial and temporal variation in the ground surface freezing index(GFI) and ground surface thawing index(GTI) from 1900 to 2017 for FGRN China, with the air freezing index(AFI) and air thawing index(ATI) using the University of Delaware(UDEL)monthly gridded air temperature dataset. The turning point year for annual mean air temperature(AMAT) was identified as 1985, and the turning point years for GFI and GTI were 1977 and 1996. The air temperature increased by 0.01 ℃ per year during 1900–2017, and the GFI and GTI increased at rates of –0.4 and 0.5 ℃ d per year before the turning point year;after the turning point, these rates were –0.7 and –2.1 ℃ d per year. We utilized a surface frost number model to study the distribution of frozen ground in FGRN China from 1900 to 2017.When the empirical coefficient E value is 0.57, the simulated frozen ground distribution is basically consistent with the existing frozen ground maps. The total area of permafrost in FGRN China decreased by 22.66×10^(4) km^(2) from 1900 to 2017, and the permafrost boundary moved northward with obvious degradation. The results of this study demonstrate the trend in permafrost boundary degradation in FGRN China, and provide basic data for research on the hydrological, climate, and ecological changes caused by permafrost degradation.展开更多
The aim of the research was to evaluate, at site scale, the influence of freezing and freeze/thaw cycles on the survival of faecal coliforms and faecal enterococci in soil, in a climate change perspective. Before the ...The aim of the research was to evaluate, at site scale, the influence of freezing and freeze/thaw cycles on the survival of faecal coliforms and faecal enterococci in soil, in a climate change perspective. Before the winter period and during grazing, viable cells of faecal coliforms and faecal enterococci were detected only in the first 10 cm below ground, while,after the winter period and before the new seasonal grazing, a lower number of viable cells of both faecal indicators was detected only in some of the investigated soil profiles, and within the first 5 cm. Taking into consideration the results of specific investigations, we hypothesise that the non-uniform spatial distribution of grass roots within the studied soil can play an important role in influencing this phenomenon, while several abiotic factors do not play any significant role. Taking into account the local trend in the increase of air temperature, a different distribution of microbial pollution over time is expected in spring waters, in future climate scenarios. The progressive increase in air temperature will cause a progressive decrease in freeze/thaw cycles at higher altitudes, minimising cold shocks on microbial cells, and causing spring water pollution also during winter.展开更多
基金supported by the Second Tibetan Plateau Scientific Expedition and Research Program(STEP)(Grant No.2021QZKK0202)Shaanxi Provincial Youth Science and Technology Rising Star Project(No.2022KJXX-85)+3 种基金Key Scientific Research Project of Shaanxi Provincial Department of Education(No.22JS041)Youth Innovation Team Research Project of Shaanxi Provincial Department of Education(Nos.22JP099,21JP137)The Youth Innovation Team of Shaanxi Universitiesthe Support Program for Outstanding Young Talents of Shaanxi Universities(Dr.Tao Luo)。
文摘Freezing–thawing indices serve as a comprehensive indicator of both the duration of the freezing/thawing periods and the degree of cold and heat in a given region.In-depth analysis of the freezing-thawing indices not only enables the prediction of permafrost distribution and its dynamic changes,but also facilitates the assessment of damage risk to infrastructure under freeze-thaw action.In this paper,the air/ground freezing–thawing indices from 1987 to 2017,based on daily temperature observations from meteorological stations along the China–Nepal Highway(CNH),were calculated,and their spatial and temporal variation patterns were analyzed.The results showed that:(1)Both mean annual air temperature and mean annual ground surface temperature along the CNH fluctuated upward,with climate tendency rates of 0.43 and 0.52.C·(10a)~(-1),respectively;(2)The number of days with negative air temperature and ground temperature showed fluctuated downward,with change rates of-8.6 and-8.3 d·(10a)~(-1),respectively;(3)The ranges of air freezing index,air thawing index,ground freezing index,and ground thawing index over the years were 157.05-458.88°C·d,2034.20-2560.73°C·d,108.78-396.83°C·d,and 3515.25-4288.67°C·d,respectively.The climate tendency rates were-5.42,10.22,-6.79,and 12.14.C·d·a-1,respectively,showing a general warming trend;(4)The air freezing index,ground freezing index,and ground thawing index changed abruptly in 1999,2000,and 2002,respectively,evincing significant changes after 2002.The research results can provide a basis for the risk assessment of freezing–thawing erosion and the prevention and control of permafrost engineering diseases along the CNH.
基金National Natural Science Foundation of China,No.41901072, No.41971151Joint Key Program of the NSFC and Heilongjiang Province of China,No.U20A2082。
文摘Against the background of global warming, environmental and ecological problems caused by frozen ground degradation have become a focus of attention for the scientific community. As the temperature rises, the permafrost is degrading significantly in the frozen ground region of northeast China(FGRN China). At present, research on FGRN China is based mainly on data from meteorological stations, and the research period has been short.In this study, we analyzed spatial and temporal variation in the ground surface freezing index(GFI) and ground surface thawing index(GTI) from 1900 to 2017 for FGRN China, with the air freezing index(AFI) and air thawing index(ATI) using the University of Delaware(UDEL)monthly gridded air temperature dataset. The turning point year for annual mean air temperature(AMAT) was identified as 1985, and the turning point years for GFI and GTI were 1977 and 1996. The air temperature increased by 0.01 ℃ per year during 1900–2017, and the GFI and GTI increased at rates of –0.4 and 0.5 ℃ d per year before the turning point year;after the turning point, these rates were –0.7 and –2.1 ℃ d per year. We utilized a surface frost number model to study the distribution of frozen ground in FGRN China from 1900 to 2017.When the empirical coefficient E value is 0.57, the simulated frozen ground distribution is basically consistent with the existing frozen ground maps. The total area of permafrost in FGRN China decreased by 22.66×10^(4) km^(2) from 1900 to 2017, and the permafrost boundary moved northward with obvious degradation. The results of this study demonstrate the trend in permafrost boundary degradation in FGRN China, and provide basic data for research on the hydrological, climate, and ecological changes caused by permafrost degradation.
基金supported by the European Union (CC-Water S project, SEE/A/022/2.1/X)by the Ministero dell'Istruzione, dell'Università e della Ricerca (PRIN2008TL25YL)
文摘The aim of the research was to evaluate, at site scale, the influence of freezing and freeze/thaw cycles on the survival of faecal coliforms and faecal enterococci in soil, in a climate change perspective. Before the winter period and during grazing, viable cells of faecal coliforms and faecal enterococci were detected only in the first 10 cm below ground, while,after the winter period and before the new seasonal grazing, a lower number of viable cells of both faecal indicators was detected only in some of the investigated soil profiles, and within the first 5 cm. Taking into consideration the results of specific investigations, we hypothesise that the non-uniform spatial distribution of grass roots within the studied soil can play an important role in influencing this phenomenon, while several abiotic factors do not play any significant role. Taking into account the local trend in the increase of air temperature, a different distribution of microbial pollution over time is expected in spring waters, in future climate scenarios. The progressive increase in air temperature will cause a progressive decrease in freeze/thaw cycles at higher altitudes, minimising cold shocks on microbial cells, and causing spring water pollution also during winter.
