Definition of Arctic and Antarctic Sea Ice Variation Index

It is well known that varying of the sea ice not only in the Antarctic but also in the Arctic has an active influence on the globe atmosphere and ocean. In order to understand the sea ice variation in detail, for the first time, an objective index of the Arctic and Antarctic sea ice variation is defined by projecting the monthly sea ice concentration anomalies poleward of 20°N or 20°S onto the EOF (empirical orthogonal function)-1 spatial pattern. Comparing with some work in former studies of polar sea ice, the index has the potential for clarifying the variability of sea ice in northern and southern high latitudes.

Extraction of lacunarity variation index for revealing the slope pattern in the Loess Plateau of China

Lacunarity analysis is frequently used in multiscale and spatial pattern studies.However,the explanation for the lacunarity analysis results is limited mainly at a qualitative description level.In other words,this approach can be used to judge whether the spatial pattern of the objective is regular,random or aggregated in space.The lacunarity analysis,however,cannot afford many quantitative information.Therefore,this study proposed the lacunarity variation index(LVI)to reflect the rates of variation of lacunarity with the resolution.In comparison with lacunarity analysis,the simulated experiments show that the LVI analysis can distinguish the basic spatial pattern of the geography objects more clearly and detect the scale of aggregated data.The experiment showed that different slope types in the Loess Plateau display aggregated patterns,and the characteristic scales of these patterns were detected using the slope pattern in the Loess Plateau as the research data.This study can improve the spatial pattern analysis and scale detecting methods,as well as provide a new method for landscape and vegetation community pattern analyses.Lacunarity analysis is frequently used in multiscale and spatial pattern studies.However,the explanation for the lacunarity analysis results is limited mainly at a qualitative description level.In other words,this approach can be used to judge whether the spatial pattern of the objective is regular,random or aggregated in space.The lacunarity analysis,however,cannot afford many quantitative information.Therefore,this study proposed the lacunarity variation index(LVI)to reflect the rates of variation of lacunarity with the resolution.In comparison with lacunarity analysis,the simulated experiments show that the LVI analysis can distinguish the basic spatial pattern of the geography objects more clearly and detect the scale of aggregated data.The experiment showed that different slope types in the Loess Plateau display aggregated patterns,and the characteristic scales of these patterns were detected using the slope pattern in the Loess Plateau as the research data.This study can improve the spatial pattern analysis and scale detecting methods,as well as provide a new method for landscape and vegetation community pattern analyses.

Thermal stability of permafrost under U-shaped crushed rock embankment of the Qinghai-Tibet Railway

The U-shaped crushed rock embankment(UCRE),of which widely utilized in the permafrost regions along the Qinghai-Tibet Railway,has the capability to rapidly reduce the ground temperature of the underlying permafrost.However,there remains uncertainty regarding the adaptation of UCRE to climate change and its long-term cooling trend.This study focuses on nine UCRE monitoring sites along the Qinghai-Tibet Railway to analyze the dynamic variations of the ground temperature underlying permafrost from 2006 to 2020.The efficiency of UCRE in stabilizing permafrost temperature in different permafrost zones is evaluated by considering the permafrost table,ground temperature,and MAGT,as well as the temperature difference between the top and bottom of the crushed rock layer and the ground temperature variation index(GTVI).The results show that UCRE is suitable for application in extremely unstable warm permafrost regions where the MAGT is higher than-0.5℃.Moreover,UCRE effectively diminishes the disparity in permafrost thermal stability between the sunny and shaded shoulders of the embankment.The short-term and long-term effect of cooling permafrost is experiencing a change related with permafrost stability.Notably,in stable cold permafrost regions with MAGT lower than-1.5℃,the long-term cooling effect of UCRE on permafrost seems to gradually di-minishes,but UCRE continues to fulfill the role of stabilizing the underlying permafrost thermal state over the long-term.These results show that UCRE can quickly restore and stabilize the thermal state of permafrost in the early stages of construction,and adapt to the influence of future climate change.The findings provide important guidance for understanding the variations of permafrost thermal stability beneath the embankment in permafrost regions,as well as for improving the embankment stability and operational safety of the Qinghai-Tibet Railway.