As a special type of glacier， surging glaciers are often related to glacier hazard events such as glacial lake outburst flood， glacial debris flow and landslide. Although only 1% of the world’s glaciers have been observed to surge， the scientific and practical significance of surging glaciers can not be ignored. In this paper， based on Landsat MSS/TM/ETM+/OLI images， ASTER stereo pair images， and ITS_LIVE data， we obtained the glacier area， elevation and velocity changes of the North Kyzkurgan Glacier in central Pamir before， during and after the surging， and revealed the complete surge process of this glacier. The results show that， the North Kyzkurgan Glacier is a typical surging glacier， which was in the quench phase during 1973—2011， in the active phase during 2011—2016. After 2016， the glacier entered a quench phase again. In the active phase of 2011—2016， the glacier terminal rapidly speeds up and advances， with marked thinning over the accumulation area and thickening on the ablation area. The active phase of the surging glacier was 6 years， the quench phase was likely about 40 years at least. The main reason behind the glacier surge may be the extremely low temperature and abundant precipitation， as was recorded at the Fedchenko Meteorological Station in 1935—1990. In addition， the accumulation area ratio of the North Kyzkurgan Glacier is more than 0.8， and the positive difference of glaciation is about 1 000 m， so the glacier material accumulation is rapidly. With the continuous thickening of glacier accumulation area which build-up by snowfall， avalanches and drifting snow， the glacier bed was raised to the pressure melting point and produced meltwater. The meltwater reduced basal drag and faster sliding， and finally led to the glacier surging. Therefore， the surging of the North Kyzkurgan Glacier was mainly caused by thermally mechanism.
In order to explore the spatial distribution and main sources of trace elements in the snow and ice of the Qinghai-Tibet Plateau， the surface snow samples at a depth of 0~5 cm collected from the Qiyi Glacier， Bayi Glacier， Gangshika Glacier， Meikuang Glacier， Yuzhufeng Glacier， Gurenhekou Glacier， and Baishuihe Glacier No.1 of Yulong Snow Mountain on the Qinghai-Tibet Plateau from July to September 2019 were analyzed to determine the concentrations of fifteen elements （Al， As， Ba， Co， Cr， Cu， Fe， Li， Mn， Mo， Pb， Sr， Tl， Zn， Cd）. The spatial distribution trend of these trace elements was presented by Jonckheere-Terpstra non-parametric test. The results showed that the Meikuang Glacier and the Yuzhufeng Glacier in the central region had the highest concentration of trace elements， while the lowest concentrations were identified in the Gurenhekou Glacier and the Baishuihe Glacier No.1 of Yulong Snow Mountain in the southern region. We compared the concentrations of As， Cu， Pb， Zn and Cd with other glaciers in the study area， and the elemental distribution generally showed the decrease trend of Central>Northern>Southern regions on Qinghai-Tibet Plateau. Enrichment factor analysis showed that Co， Cr， Cu， Tl， Fe， Li， Mn， Mo and Sr were mainly affected by dust input， while Pb， Cd and Zn were more affected by anthropogenic sources （i.e. non-ferrous metal smelting， traffic emissions and fossil fuel combustion）. The backward trajectory indicated that the three glaciers in the northeastern region were mainly affected by the air mass originated from northeastern and northwestern regions. The air mass source of the central glaciers was mainly from the dust input from the western and northern Qinghai-Tibet Plateau， which was influenced by the nearby coal mines. The two southern glaciers were mainly influenced by South Asia and the southwestern part of the Qinghai-Tibet Plateau. This research could expand the trace element database of snow and ice on the Qinghai-Tibet Plateau， providing scientific understanding for assessing the pollution of the Qinghai-Tibet Plateau’s atmospheric environment derived from human activities and the potential environmental risks of water source areas.
Based on the analysis of the index of very wet day precipitation （R95p） at 71 stations in the central and eastern part of the Qinghai-Tibet Plateau， unvariate linear regression and synthetic analysis were used to conclude the result： the R95p is increasing in recent years. In high value years of R95p， the poleward movement of the westerly in the middle latitude and easterly in the tropical region are strengthened. Meanwhile， the moisture transport of the south Asian monsoon increased and enhanced at the south of the Qinghai-Tibet Plateau with upper layer abnormal anticyclonic circulation， abundant water vapor and strong updraft together caused the convergence of water vapor strengthened in the eastern parts of the Qinghai-Tibet Plateau. In high value years of R95p， vice versa. Through further discussion and analysis， we have obtained a mechanism that can influence the R95p changes on the Qinghai-Tibet Plateau： When the storm track in the North Atlantic region intensifies， the forcing effect of the transient eddy on the basic airflow is strengthened which accelerated the mid and high latitudes westerly. Furthermore， the instability energy in the exit of the North Atlantic jet generated an anomalous high pressure in northwestern Europe， which in turn affected the monsoon systems through the Rossby wave train. Finally， regulated the R95p in the central and eastern parts of the Qinghai-Tibet Plateau. Research on the relationship between the R95p and large-scale circulation on the Qinghai-Tibet Plateau can provide a certain reference for long-term forecasting.
The infiltration law of active layer soil in permafrost area of Qinghai-Tibet Plateau is the main content of soil water cycle process in alpine region. In this study， the active layer soil of alpine swamp meadow， alpine meadow and alpine grassland in permafrost area of Qinghai-Tibet Plateau was selected as the research object， and the bare land was used as the reference object to analyze the infiltration law of soil with different vegetation types and its main influencing factors. The results showed that the infiltration capacity of soil of different vegetation types： alpine grassland > bare land > alpine meadow > alpine swamp meadow. This shows that the dense roots in the alpine meadow soil have a strong blocking effect on the movement of soil water and reduce the infiltration performance of the soil， while the roots in the alpine grassland are sparse， the blocking effect on soil infiltration is weak， and the leakage rate of soil water to the deep layer is large. By comparing the simulation results of four soil infiltration models， it is found that Horton model is the most suitable to describe the infiltration process of soil water in alpine grassland. In addition， the simulation of different infiltration models in the process of bare land infiltration is better than that of other vegetation types， indicating that vegetation types and plant growth conditions affect the simulation effect of soil infiltration process. The study on soil infiltration process in permafrost region will provide parameter support for the land hydrological process model of permafrost area of Qinghai-Tibet Plateau under the condition of global warming， and provide basic data for the study of water resources change in the future.
Due to the effects of climate warming， wetting， freezing and thawing， landslides occur frequently in eastern Tibet in recent years， which poses a serious threat to the safety of people’s lives and property safety and restricts the local economic and social development. Therefore， an effective method of large-scale landslides hazards investigation and early identification is required urgently. In this study， using Small Baseline Subset （SBAS） InSAR method and sentinel-1A ascending and descending SAR images acquired from March 2017 to July 2019， the surface deformation and distribution of landslide hazards in this area is achieved， and the characteristics of historical deformation evolution and causes of landslide are investigated as well. The results show that： （1） Most of the areas are relatively stable， and the potential landslide hazards mainly concentrate on both sides of the valley. The accuracy and coverage of landslide monitoring and identification are improved by combining ascending and descending InSAR. （2） The deformation process of the freeze-thaw landslide is different from that of the rainfall-induced landslide， showing the seasonal variation characteristics of the stable and the instable period alternatively. （3） The deformation development is mainly affected by freeze-thaw and rainfall process， and both of them accelerate the slope displacement. The results suggest that InSAR technology can be an effective alternative for the shortcomings of traditional monitoring methods， and can play an important role in the early identification， monitoring and prevention of landslide hazards in alpine permafrost regions.
The Qinghai-Tibet Railway （QTP） embankment was constructed based on the method of active cooling embankment. At present， the railway has been safely operating for more than 10 years. The subgrade of QTP is built on the permafrost， and temperature change of the permafrost under the subgrade is a key factor in measuring the stability of the subgrade. Based on the long-term （2008—2019） observation， the permafrost table and the annual ground temperature in five boreholes which were drilled within 30 m range to the slope foot mileage K980+000 was analyzed. Inter-annual ground temperature changes and seasonal temperature changes were analyzed and the long-term effects of engineering behavior on cold permafrost were examined. The results show that the permafrost temperature has been increasing and permafrost table has been decreasing. Compared with the natural hole， the ground temperature of the borehole at the foot of the slope is less increased by the cooling effect of the roadbed. The cold season and the warm season are asymmetrical. Due to the consideration of the protection of permafrost and the stability of the project， the roadbed should be built with the idea of cooling roadbed as much as possible， so that the ground temperature at the foot of the roadbed slope is lower than the temperature of the frozen soil under the natural state， but the roadbed of the frozen soil is generally warmed. The trend still exists. At the same time， the monitoring of the subgrade should be strengthened， the stability of the subgrade after the long-term warming process should be analyzed， and the quantitative study on the change of the frozen soil under the subgrade should be processed.
Major engineering construction will disturb the alpine grassland. The regulations require that the turf layer in the disturbed area should be stripped and used to restore the native vegetation after the construction of the project. At present， there is little research on the survival impact of stripped turf stacking. By studying the effects of shade net and perforated film on the soil temperature and humidity and greening coverage of the stripped turf blocks after stacking and replantation， the results show that the temperature of shade net mulching stockpile is significantly lower than the daily average soil temperature of the natural ground， and greatly prolonged the freezing period of each depth layer， the supplementary effect of precipitation on soil moisture is delayed， and a large amount of water loss during the stacking period； perforated film mulching stockpile had higher soil temperature compared with the natural ground， and hinders the supplementation of soil moisture by precipitation， the soil water holding capacity is decreased； the greening coverage of the shading net mulching turf block is significantly higher than that of the perforated film. There is good linear correlation between the number of stacking days with daily average soil temperature > 0 ℃ and the greening coverage of turf blocks. The stacking time should be shortened as much as possible in the construction of engineering construction， and permeable and breathable mulching material should be used to increase the heat exchange between the soil and the air to maintain a longer freezing period， and timely add water to improve the revegetation effect of turf block replantation.
Atmospheric nitrate （particulate nitrate + gaseous HNO3） plays an essential role in the biogeochemical cycle of nitrogen in the Arctic region. However， there are poor studies on the formation mechanisms of atmospheric nitrate over the Arctic Ocean， which limits our understanding of atmospheric chemical processes related to nitrogen oxides （NOX=NO+NO2） and nitrate in this area. As part of 5th Chinese National Arctic Research Expedition （CHINARE） in the summer of 2012， aerosol filter samples were collected and nitrogen and oxygen isotopes of nitrate （δ15N， δ17O and δ18O） in the filter samples in 62.3°~74.7° N were analyzed to trace the formation pathways of atmospheric nitrate over the Arctic Ocean. The observed daily Δ17O（NO
Trace elements recorded in snow cover can be a good assessment of local air pollution. Using inductively coupled plasma mass spectrometer （ICP-MS）， 16 trace elements were detected in snow cover samples collected in January and March 2018 from the northern slope of Tianshan Mountain， Yili River valley， Tacheng region and Altai region in northern Xinjiang. It is shown that the average of trace elements in the snow cover in northern Xinjiang is between 0.06 ng·g-1（Cd）~1 481.1 ng·g-1（Al）. In terms of time distribution， most trace element concentration during the ablation period is lower than the accumulation period and stable period； and the ablation period content of some elements of Pb， Cr is higher than other periods， which may be related to external input. In terms of spatial distribution， most trace elements in the Tacheng area and the northern slope of Tianshan Mountain are 1~3 times higher than that in the Yili River Valley and Altai region. Compared with the content of trace elements in the snow ice in other regions， it was found that northern Xinjiang is 1~3 times higher than the northern Tibetan Plateau， and the corresponding trace elements concentration is close to the No. 1 Glacier of Urumqi River of Tianshan Mountain， which is greatly affected by human activity， revealing the high concentration characteristics of trace elements in the snow in northern Xinjiang. Elemental enrichment coefficient indicates that elements like Fe， Be are mainly from crust dust， and elements like Pb， Cd， Zn， As are significantly enriched （EFc>10）， dominated by human emission activity. The backward air mass trajectory shows that trace elements in Tacheng area may be affected by Kazakhstan， and trace elements in Altai area may be affected by Central Asia， the southern edge of Altai Mountains and other places， and the northern slope of Tianshan Mountain and Yili valley are mainly dominated by the local gas mass in Xinjiang.
Based on the measured wind speed and wind direction data from 19 manned weather stations during 1961—2017， the temporal and spatial variations of near-surface wind speed and wind direction over the Antarctic ice sheet were analyzed. The results show similar spatial variability patterns between seasonal and annual mean near-surface wind speeds over the Antarctic Ice Sheet from 1961 to 2017. The wind speeds in the coastal area of 0°~120° E sector of East Antarctica showed a significant upward trend. The sign and magnitude of trends in the wind speeds from 6 meteorological stations on the Antarctic Peninsula are different. Both annual and seasonal wind speeds averaged over the 6 stations exhibited upward trends during 1961—2017. The upward trends were related to local warming， decline in the sea level pressure， and the positive polarity of the southern annular mode in recent decades. Southerly or easterly winds prevailed in most areas of East Antarctica， and the wind directions were stable. On the Antarctic Peninsula， influenced by frequently synoptic activities， the wind directions are variable， and it is not easy to determine the dominant wind direction.
Snow cover is an essential parameter in the Earth’s energy budget and hydrological cycle. Snow cover in the High Mountain Asia provides a significant contribution to runoff in many populated areas， where it represents a primary source of drinking water for billions of people across Asia and supports irrigation， the industry and energy production. Taking the High Mountain Asia as the study area， the cloud removal of the daily MODIS snow cover products during 2000—2020 is firstly carried out. On this basis， the snow-covered days （SCD）， snow onset date （SOD）， snow end date （SED） and snow duration days （SDD） for each hydrological year （from September 1 to August 31 in the next year） are extracted. Finally， the spatiotemporal dynamics of snow phenology and its response to climate change are analyzed. The following results are found： （1） The snow phenology in the High Mountain Asia shows a great spatial difference and a vertical zonality mainly influenced by the altitude. SED is mainly concentrated in March-June. In the low-altitude areas， SED appears in March or earlier， while it is delayed to June or later in the high-altitude mountainous areas. SOD is mainly concentrated in September-December. SOD appears earlier in the high-altitude mountainous areas and high-latitude areas， while mainly appears in November or later in the low-altitude areas. （2） During the 20-year period， SDD in the study area mainly shows a shortening trend. Up to 13.5% of the area of SDD shows a significantly shortening trend， while only 7.4% of the area shows a significantly lengthening trend. SED in the study area mainly shows an advanced trend. Up to 15.8% of the area of SED shows a significantly advanced trend， while only 8.8% of the area is significantly delayed. SOD in the study area mainly shows a delayed trend. 11.4% of the area show a significantly delayed trend， while 8.2% of the area is significantly advanced. （3） The interannual variation of snow phenology in the High Mountain Asia has an obvious response relationship to climate change， and shows different response degrees in different subregions. The temperature of snow accumulation period is the dominant factor affecting the interannual variation of SOD， and the temperature during snow melt period is the dominant factor affecting the interannual variation of SED. The increase of temperature leads to the delay of SOD， advance of SED and shortening of SDD.
Glacier albedo directly governs the net shortwave radiation flux at the glacier surface and largely determines the surface energy balance over entire glacier. Surface albedo is one of the important drivers of surface processes that promote glacier melting. Therefore， it is important to investigate the temporal and spatial variation of the glacier albedo for simulating the glacier melting. In this study， spatial and temporal variations of albedo were investigated using Landsat images， MODIS daily albedo products and the albedo measured by an Analytical Spectral Device on the Urumqi Glacier No.1 in eastern Tien Shan， China， during May and August， 2016. The data suggested that the spatial distribution of surface albedo was not observed in the early ablation season. However， in the middle or later ablation season， it varied remarkably and generally increased with elevation， especially around the equilibrium line. Temporally， the fluctuation of surface albedo was obvious with from 0.70 to 0.17， a generally decreasing trend was shown. The profile of daily albedo variations was different at various sites on melting glacier surface. The largest daily variation in albedo occurred near the snow line， and followed at the snow sites. A trend of mild fluctuating daily albedo values was shown at ice sites. Most of these variations were induced by the transition in dominant surface type from snow to bare ice， and these transitions in dominant surface type were driven by the air temperature and snowfall. Over bare ice surface， the albedo significantly decreased as the concentrations of surface dust increased， particularly in the visible wavelength. Moreover， the spatial change in surface albedo was related to slope and aspect， because the solar incident angle is dominated by slope and aspect， the surface albedo obviously increases with the solar incident angle on the assumption that the surface condition is uniform.
Studying the response mode of glacier area changes to temperature changes is of great significance to the protection and utilization of glacier resources. Glacier outlines of eight periods from 1973 to 2020 in the Altun Mountains were delineated in a semi-automated manner using band ratio images of Landsat MSS， TM and OLI scenes. The spatial-temporal characteristics of glacier changes were analyzed. The meteorological data from four meteorological stations， namely， Qiemo， Ruoqiang， Mangya and Lenghu， around the study area were utilized to investigate the responses of glacier to air temperature changes. We found that in general， the glaciers were shrinking in the Altun Mountains from 1973 to 2020 and the glacier area decreased （64.89±12.36） km2（19.21%±2.90%）. The glaciers retreated faster from 1973 to 1990 with an annual shrinking rate of （0.49±0.07）%·a-1 and the fastest in two periods of 1990—1995 and 1995—2000 than other time periods with annual shrinking rates of （1.07±0.08）%·a-1 and （1.08±0.08）%·a-1， respectively. After 2000， the glaciers shrank slowly and were relatively stable， with an annual shrinking rate under 0.2%·a-1. Air temperature was the main climatic factor affecting glacier changes in the Altun Mountains from 1973 to 2020. The response mode of the glaciers in the Altun Mountains to air temperature changes was： during the air temperature rising stage， the glaciers were melting， and the area of glaciers was decreasing； during the air temperature stable stage， the glaciers gradually reached a new dynamic equilibrium state， and the area of glaciers was relatively stable； during the air temperature decreasing stage， due to hysteresis of glacier movement， the area of glaciers would not change significantly in a short period of time.
The change of snow depth plays an important role in the surface water heat balance. Five global climate models from Phase 6 of the Coupled Model Intercomparison Project （CMIP6） with relatively complete scenarios are selected to evaluate the simulation ability of the climate model in simulating the snow depth in Xinjiang by comparing the long time series data sets of the snow depth in Xinjiang from 1979 to 2014. The change of snow depth in Xinjiang during 2021—2040 （recent period）， 2041—2060 （middle period）， and 2081—2100 （late period） relative to the base period （1995—2014） under different SSPs-RCPs scenarios in the future is also estimated. Temperature and precipitation have an important impact on the change of snow depth， so the change trend of temperature and precipitation in Xinjiang to the end of the 21st century is also analyzed. The results show that： （1） The correlation coefficients between the snow depth data simulated by the revised climate model and the observed data are all above 0.8， and the results from January to March are more consistent with the observed data. The climate model can basically reflect the basic characteristics of annual variation of snow depth. The spatial distribution of snow depth simulated by the climate model has similar characteristics with the observed data. （2） Temperature and precipitation will rising volatility under different scenarios in the future， the increase of temperature is relatively obvious， reaching 0.43 ℃·（10a）-1， while the increase of precipitation is 0.63 mm·（10a）-1. （3） In general， the climate of Xinjiang in the future will show a warming and wetting trend. The average snow depth in Xinjiang will increase in different periods in the future. Under SSP1-1.9 scenario， snow depth will increase in most northern regions in the near， middle and late 21st century. Under SSP1-2.6 scenario， the snow depth in the northern Altai Mountains will decrease in the recent century， but will increase in the middle and end of the 21st century. Under SSP2-4.5 scenario， the snow depth in eastern China will increase in different periods in the 21st century， while the snow depth in most of northern and central China will decrease in different periods. Under SSP3-7.0 scenario， the snow depth in north and southwest China will generally decrease， while the snow depth in eastern China will generally increase in different periods in the 21st century. Under the SSP4-3.4 and SSP4-6.0 scenarios， the snow depth in southwest Kunlun Mountains will generally decrease in different periods in the 21st century， while the snow depth in eastern Kunlun Mountains will generally increase. Under the SSP5-8.5 scenario， the snow depth will generally increase in the northern Altai Mountains and eastern regions.
Many extreme floods are caused by the rain-on-snow （ROS） events in the world. Under global warming， the rain-on-snow （ROS） event and its flood have increased and would increase in the future. It is of great significance to understand the spatiotemporal variation of ROS for flood control and disaster reduction. Based on the daily temperature， precipitation， snow depth， weather phenomenon and other meteorological observation data of 42 national meteorological stations in northern Xinjiang from 1960 to 2015， the parameterization scheme of rain-on-snow （ROS） events was determined by using precipitation type， ground state and snow depth records. On this basis， the spatiotemporal variation characteristics of ROS days and their relationship with temperature and elevation in northern Xinjiang were analyzed. The results show that during the last 56 years， the rate of 0.3 d·（10a）-1 of ROS days in northern Xinjiang has been increasing slowly； In terms of spatial distribution， ROS in northern Xinjiang is mainly concentrated in the north of Tacheng， Ili River Valley and the headwaters of Urumqi River. Yumin county has the most ROS events， with an annual ROS day of 12.2 d； Correlation analysis showed there was a significant positive correlation between the number of ROS days， ROS amount and altitude. This study is expected to improve the scientific understanding of the snow surface rain event， which is an important phenomenon of inducing rain and snow mixed flood in arid area of Xinjiang， and provide a reference for the analysis of disaster causing flood process and flood monitoring and early warning in our region.
In order to explore the distribution characteristics of active layer thickness （ALT） in permafrost areas along the Qinghai-Tibet engineering corridor， combined with the ALT monitoring data of 300 drilling points along the Qinghai-Tibet Highway and Qinghai-Tibet Railway， Using annual average surface temperature， average vegetation index， equivalent latitude， latitude， elevation and ice content as analysis parameters， prediction models based on the empirical formula， random forest and radial basis function （RBF） neural network method are developed. The results of each prediction model show that the ALT has a strong non-linear relationship with each prediction factor； the RBF neural network prediction model has the highest prediction accuracy， and the goodness of fit （R2） reaches 0.84. Utilizing the developed RBF neural network prediction model and high-precision remote sensing data， the ALT distribution map of whole Qinghai-Tibet engineering corridor has been obtained. The distribution map shows that the thickness of active layer in the study area is mainly 2~4 m， with area of 5 468.3 km2， accounting for 47.27% of the total area， and mainly distributes in Chumar River Plain， Beiluhe Basin， Tanggula Mountain， and Touerjiu Mountain； subsequently， the conditions of ALT larger than 4m has the area of 3 382.3 km2， accounting for 29.24% of total， the overall distribution of which is biased towards the southern region and mainly in Buqu River valley to Touerjiu Mountain. Finally， the relations among the ALT， ice content and ground temperature of the study area have been researched. The results show that the ALT decreases with the increase of ice content and increases with the increase of ground temperature.
Besides being an important part of cryosphere， the permafrost in the northern Greater Khingan Mountains is the only permafrost region at the mid-to-high latitudes in China. Analysis on the hydrothermal characteristics in this region is of great significance to the research of land-atmosphere energy exchange， terrestrial ecosystems， and climate change. Based on the air temperature， ground temperature and moisture content at the depths between 0-2 m collected in a wetland permafrost near the Greater Khingan Mountains Forest Ecological Station from 2011 to 2020， the heat and water transferring characteristics of the permafrost active layer in the Greater Khingan Mountains wetland were analyzed. Results show that the varying range of ground temperature in the active layer of the wetland permafrost decreases with depth and has a significant hysteresis. The ground surface temperature is higher than that at deep depths during the ground thawing period， and it is opposite during the ground freezing period. The average ground thawing velocities were 0.49， 0.61， 0.47， and 0.56 cm·d-1 in 2012， 2013， 2019， and 2020. The corresponding average upward ground freezing velocities were 1.34， 2.12， 2.58， and 1.65 cm·d-1， respectively. The average downward ground freezing velocities were 1.69， 1.02， 3.32， and 1.00 cm·d-1， and the maximum thawing depths of the active layer were 78.73， 85.65， 66.22， and 74.94 cm， respectively. From May 2012 to May 2013， the soil moisture content remained much correlated with the ground temperature. During the freezing period， the unfrozen soil water content was related with the ground temperature in a good power function， and the correlation coefficient is greater than 0.90， and the fitting result for deep soil is better than that at surface soil. During the thawed period， the correlation between the soil moisture content and ground temperature is not good and the correlation coefficient is less than 0.50. In addition， the correlation coefficient decreases with depth. Sufficient soil moisture in the wetland is in favor of the bidirectional freezing in the permafrost active layer. In the depth less than or equal 1.4 m， the ground temperature is strongly correlated with the air temperature. As a strong thermal insulation material， the snow dampens the ground temperature variation with air temperature in winter and somehow keeps the ground ‘warm’. The process of snow melting delays the ground from thawing. Besides， the vegetation layer will impede the solar radiation arriving the ground surface and decrease the ground surface temperature， which will weaken the correlativity between air and ground temperatures and preserve the permafrost. This study will provide a good data basis and theoretical advanced investigation for modelling the ground freezing and thawing with consideration of both heat and water transferring in a coupled way the permafrost regions of the Greater Khingan Mountains wetland.
In order to study the impact of freeze-thaw on foundation trenches in seasonally frozen regions， a numerical platform for stability analysis is established based on the theory of thermal transport with the consideration of ice-water phase and modified cam-clay model considering cohesion and strength reduction method. By comparing the numerical and experimental data of foundation trench cases with different initial dry unit weights， the deformation and stability as well as the changes in physical-mechanical parameters of the soil induced by freeze-thaw are analyzed. The results show that： 1） the freeze-thaw causes a notable local deformation， 2） the original dry unit weight has a great influence on the deformation characteristics， and 3） the freeze-thaw induces a negligible change in safety factor. The freeze-thaw induced horizontal displacements of piles are relatively small when the original unit weight approaches the critical state （γd0）， and the displacements increase when the original dry unit weight deviates from the critical one. The horizontal displacements of piles increase with the increase of the discrepancy between the initial and critical dry unit weights. For the cases with relatively lower initial dry unit weights， larger vertical settlement but smaller basal heave are found. The research results will benefit to the design and construction of foundation trenches in seasonally frozen regions.
Xinjiang is an important part of the arid Central Asia， which responds sensitively to the global climate change and has the water resources problem severely. Studying the impact of climate change on water resources in Xinjiang has a significant effect on the adaptability of future climate change and water resource security. Based on the latest climate-hydrological observations and research results， this paper analyzes the characteristics of hydrological and climate change and the impacts of climate change on water resources， and discusses the main problems and countermeasures. Results indicate that： （1） Temperature in Xinjiang had a significant increasing trend during 1961—2018， and the increase rate of temperature was higher than the global average and the winter change could be the most important factor for the rise in annual air temperature. Precipitation and number of precipitation days had increased obviously， especially in summer. However， both temperature and precipitation had fluctuated with high level frequency， and the sharp increasing trend had retarded since the 21st century. The climate experienced a transformation from warm-wet to warm-dry， with a intensifying drought. （2） The number of extreme maximum temperature， extreme minimum temperature and high temperature days had increased significantly since the beginning of 21st century. The first day of high temperature was brought ahead， the last day of high temperature was postponed， and the intensity and frequency of extreme precipitation events and rainstorm snow had increased significantly. （3） Under the influence of climate change and human activities， the runoff in sources of the Tarim River basin had increased obviously. The water of the Bosten Lake had expanded since 2013. The Ebinur Lake had shrunk and the Sayram Lake had been expanded steadily. The glaciers had been generally retreated with great regional differences， specially in the Tianshan and Altai Mountains. （4） There are main problems of climate and hydrological changes in Xinjiang， such as unclear understanding of climate change trends and physical processes， difficult to handle the increased risk of hydro-meteorological disasters， the uncertainty in the impact of climate change， especially， the water security. （5） It is suggested to seek the advantages and avoid the disadvantages， to seize the climate opportunity and to speed up the construction of ecological environment. Seizing the climate opportunity， let us to carry out comprehensive investigations on climate and hydrology system， to strengthen mechanisms research， to build a coordinated comprehensive observations network and to improve the ability to control the risks of hydro-meteorological disasters. It is necessary to take effective and orderly adaptation to climate change to a strategic level to serve the building of a beautiful Xinjiang and high-quality development.
As a solid reservoir， glaciers play a significant role in regulating the variation of runoff abundance and dieback in the form of “peak-cutting and valley-filling”. The hydrological regulation function of glaciers is very important in cold regions， especially in the arid regions of Northwest China. The runoff estimation data from 2014 to 2100 were simulated by the VIC-CAS model in the cold region of western China. With perspectives of combinations of trend and fluctuation characteristics， glacier hydrological regulation index （GlacierR） was constructed based on the runoff variation coefficient method to analyze the stability of glacier runoff in 9 cold region basins of western China. The changes of the hydrological regulation function of glaciers in these basins are analyzed in detail during the historical period （1971—2010） and in the future to the end of the 21st century. The results show that： In the historical period and under the RCP2.6 and RCP4.5 scenarios， except for the Yangtze River basin， the decrease time node of glacier runoff in other basins of the Tibetan Plateau is 2020s， and that in the northwest inland basins is 2010s. In historical period and under the global emission scenarios of RCP2.6 and RCP4.5 to the end of the 21st century， although the glacier runoff in most of cold region basins in western China showed a decreasing trend， the fluctuation range decreased or had no obvious change， and the stability of glacier runoff increased or had no change. Overall， hydrological regulation function of glaciers is high in the northwest inland river basins， while function is low in the basins of the Qinghai-Tibet Plateau. Under the global emission scenarios of RCP2.6 and RCP4.5， to the end of the 21st century， the hydrological regulation function of glaciers showed a weakening trend in all cold region basins of western China， and the weakening was more significant in the inland river basins of Northwest China. Under the global emission scenario of RCP4.5， the hydrological regulation function of glaciers in the Muzati River decreased by 25.4%， and all the basins of the Qinghai-Tibet Plateau remained at a low level. With the perspective of decadal variation， the hydrological regulation function of glaciers in the cold region basins of western China was strong during the period of 1970s—2010s， especially in the 1980s and 2000s. Under the global emission scenarios of RCP2.6 and RCP4.5， the hydrological function of glaciers showed a weakening trend obviously in the future to the end of 21st century. The earliest time node in the cold region basins is 1970s， and the latest is 2020s.
Cold regions are widely distributed in China， most of which are the headwaters of major rivers of China. Their runoff evolution will have an important impact on the regional even the whole country water resources. Aiming at the special hydrological characteristics under the action of frozen soil in cold region， five representative watersheds in cold regions including in Songhua River， Yellow River， Heihe River， Yangtze River and Yarlung Zangbo River basins are selected. The improved WEP-L model is used to simulate and analyze the temporal and spatial variation of runoff in cold region from 1960 to 2010. Meanwhile， based on the hydrological simulation method， different climate change and land use scenarios are designed to analyze the attribution of runoff changes in cold regions. The results show that： （1） The improved WEP-L has a good fit for runoff in different cold regions. The Nash efficiency coefficient is above 0.72， and the absolute relative error is within ±11%. （2） The trend of runoff change in five typical basins is not significant， but the base flow index of Tangnaihai and Yingluoxia increased significantly， and passed the 0.01 significance test， indicating that the proportion of basal flow in these two basins is increasing. （3） In addition to the A’yanqian and A’nen watershed of the climate change in the four cold basins has a greater impact on runoff， more than 78%， which is the dominant role in runoff evolution. Relevant studies can provide reference for the study of water cycle and water resources evolution in cold regions.
Vegetation and permafrost jointly maintain the cold and humid environment in the Greater Khingan Mountains. With global warming， the permafrost in the Greater Khingan Mountains has been severely degraded， and the growth of vegetation has also been affected. In order to further explore the relationship between vegetation and permafrost in the Greater Khingan Mountains， this study set up 55 sampling points in the permafrost regions of the North Greater Khingan Mountains， and at each sampling point we collected indicators such as the active layer thickness （ALT）， the biomass of understory shrubs， and the diameter of larch trees at breast height. Then we used the enhanced vegetation index （EVI） to compare the vegetation growth status of predominantly continuous permafrost and permafrost with isolated taliks at a regional scale. The results show that： （1） The average of ALT in Heilongjiang Huzhong National Nature Reserve is （0.47±0.14） m， and the ALT around the reserve is （0.83±0.38） m. The ALT around Heilongjiang Huzhong National Nature Reserve is greater than that in the reserve. The ALT in predominantly continuous permafrost is （1.04±0.47） m， which is less than （1.40±0.41） m in permafrost with isolated taliks. （2） The average biomass of Heilongjiang Huzhong National Nature Reserve and surrounding shrubs are （201.75±71.70） g·m-2 and （259.10±111.14） g·m-2， respectively， and the average ratios of diameter at breast height to tree age are （0.20±0.08） and （0.26±0.14）， respectively. The average biomass of understory shrubs in predominantly continuous permafrost and permafrost with isolated taliks regions are （128.31±63.33） g·m-2 and （199.04±66.13） g·m-2， respectively， and the ratio of diameter at breast height to tree age was （0.30±0.13） and （0.59±0.21）， respectively. In areas where the ALT is large， the biomass of shrubs and larch diameter at breast height are greater than those in the areas where the ALT is smaller， indicating that the increase in the ALT can promote the growth of shrubs and trees to a certain extent. （3） The results of EVI show that vegetation growth and vegetation coverage in permafrost with isolated taliks are better than those in predominantly continuous permafrost region. The study proves that at the regional scale permafrost has a restrictive effect on vegetation growth. The results of this study are of great significance for in-depth understanding of the relationship between permafrost changes and its environmental effects.
Taking Hequ alpine meadow， which located in the east of Three-River Headwaters region， as the research object. Discussed the effect of humid level on forage yield by analyzed the changes of temperature， precipitation， potential evapotranspiration， humid index and forage yield from 1991 to 2015. The results shows that： （1） From 1991 to 2015， the potential evapotranspiration of Hequ alpine meadow was increased at a rate of 3.5 mm·a-1 （P<0.01）； The precipitation was increased as a non-significant rate of 2.3 mm·a-1 （P>0.05）， and the humid level remained stable as a semi-humid climate（mean value of years is 0.52 ）. （2） In the past 25 years， the average dry yield of forage was 303.7 g·m-2 and decrease ratio was 3.0 g·m-2·a-1. （3） By analyzing the correlation between forage yield and climatic factors which affecting the humid level， it was found that air temperature has less impact on forage yield and precipitation showed a positive correlation （P>0.10） that indicating precipitation is the metal factor which influenced the forage yield. Forage yield showed a negative correlation with potential evapotranspiration （P>0.10） and a positive correlation with humid index （P>0.10）. During the growing season， forage yield showed a significant correlation with all factors except air temperature means production is quite sensitive to the wetness of regional environmental conditions.
The source regions of Yangtze ，Yellow and Lantsang Rivers over the Tibetan Plateau is recognized as 'water tower' of China and Asia. It is an important ecological security barrier and water security guarantee in China. It is the common source of the Three River Economic Belts， the strategic region of stabilizing the Tibet and consolidating the Xinjiang from the perspective of national unity， and a strategic highland of Beautiful China construction. Mastering the construction process of Beautiful China in this area， finding out the existing problems， and summing up the typical successful cases in time will help to better build the beautiful plateau， serve the construction of ecological civilization and the high quality development of social economy. As far as the content and process of construction are concerned， the construction of Beautiful China in the whole sources regions of Three Rivers is still in the stage of material construction， which lacks other industries except animal husbandry， neglects cultural construction， and lacks connotation of beauty. As far as the construction effects are concerned， beautiful village and beautiful town project construction has made remarkable achievements， but the supporting facilities lag seriously behind， as well as the conflict between nomadic culture and settlement culture， the beauty is still a mere formality. Despite these problems， a number of successful cases have emerged， especially the Ganglong Model and the Ganda Model， which provide a sample and development inspiration for the construction of beautiful China in other areas. The inspirations of the success of plateau Beautiful China construction are that： （1） advantages resources are the material basis； （2） leaders / teams / getting rich leaders are the key core； （3） the industry is strong support and operation mechanism adapted to local conditions is only sustainable way； （4） continuous exploration is the solid driving force.
The areas along the Sichuan-Tibet Railway， which is under comprehensive planning and construction， was selected as the study area in this paper. Based on the data collected from field surveys of population， regional gross domestic product （GDP） and industrial structure during 2000―2015， Nich index was used to measure the relative development of the economy， and Theil index and Gini coefficient were respectively used to analyze the changes of regional economic disparity from the perspectives of space and industry. The following conclusions can be drawn： The economy along the Sichuan-Tibet Railway has developed rapidly in the past 15 years， and the growth rates were higher than the national average level. However， they had obvious characteristics of staged changes. Compared with the decline of economic growth in Western Sichuan， the decline in Eastern Tibet was more moderate after 2012， because of the foreign aid economy. From the spatial perspective， the economic disparity in the study areas had increased， decreased， increased and decreased， and economic development was tending to be coordinated. The internal disparity was the root cause of regional economic disparity， and the contribution of internal disparity to the total economic disparity was over 94%. The internal economic disparity in Eastern Tibet is greater than it in Western Sichuan. From the perspective of industrial decomposition， the economic disparity along the Sichuan-Tibet Railway had increased， decreased， and increased. The disparity between the three industries was the tertiary industry > the secondary industry > the primary industry， and the contribution rate to the total disparity was the tertiary industry > the secondary industry > the primary industry， too. However， the gap between the contributions of the secondary industry and the tertiary industry was narrowed. The regional concentration effect dominated the changes in the overall economic disparity. It can be identified that the change in regional concentration effect of the secondary and tertiary industries， especially the tertiary industry， was a decisive factor in the overall change of economic disparity.
As one of the key factors to measure the competitiveness of a tourist destination， tourist satisfaction has been concerned by many tourism researchers. However， in the hot spot research of tourist satisfaction， there are few researches on tourist satisfaction of glacier tourism and the differences of satisfaction among different tourist attributes. In this paper， Dagu Glacier and Hailuogou Glacier were selected as the study area. Through the subdivision of tourist attributes， the fuzzy multi-criteria decision-making （F-MCDM） method and the demand elasticity theory were used to make a comprehensive evaluation and sensitivity analysis for glacier tourist satisfaction， and the countermeasures and suggestions for improving glacier tourist satisfaction were discussed. The results showed that the actual satisfaction of tourists in Dagu Glacier was higher than that in Hailuogou Glacier， and the satisfaction of management and service was the highest in both places， while the consumption and transportation satisfaction were the lowest. As far as the relative satisfaction of tourist attributes was concerned， male satisfaction was higher than female satisfaction， high consumption tourists satisfaction was higher than low consumption tourists satisfaction， and high loyalty tourists satisfaction was higher than low loyalty tourists satisfaction. The differences of relative satisfaction between the two places were reflected in age， education level， tourist source， and number of visits. Compared with Dagu Glacier， the satisfaction sensitivity of Hailuogou Glacier was higher， and the improvement of tourist satisfaction was more obvious and efficient under the same improvement intensity. As for the landscape features with the highest satisfaction sensitivity in both places， 1% improvement of Dagu Glacier would increase tourist satisfaction by 0.30%， while Hailuogou Glacier could increase tourist satisfaction by 0.45%. For different tourist attributes， the highest sensitivity of satisfaction was found among the tourists who were unwilling to recommend， unwilling to revisit and did not meet expectations. Finally， based on the results of satisfaction sensitivity analysis， some special suggestions were put forward for the development of glacier tourism in the two places， such as key attribute improvement， marketing strategy innovation， and tourism product development.
The earth system is driven by global climate change combined with human activities. Compared to the spatial data related to climate change has been greatly developed in data collection， preparation methods， spatial-temporal resolution， data quality， and so on， the data of human activity intensity is still in the stage of exploration. The spatial data of human activity intensity will not only help to understand the intensity and scope of human activities but also distinguish the impact on the earth surface between human activity and climate change. Furthermore， it is also of great significance for regulating human activities and regional sustainable development. In this paper， according to review the study of the spatial data of human activity intensity in recent decades， we first introduce the concept of the spatialization of human activity intensity. Then we make a summary of the spatialization method of human activity intensity， which can be divided into two categories： direct spatialization based on human activities and indirect spatialization based on indicators of the earth system. Meanwhile， we gave a detailed description of several methods that are widely applied， including HANPP （Human appropriation of Net Primary Production）， land use/cover change， MGDI （MODIS Global Disturbance Index） and HFI （Human Footprint Index）， and taking the Qinghai-Tibet Plateau as an example for spatial data demonstration and analysis. Finally， we discuss the current problems with the study of the spatialization of human activity intensity and give our suggestions for future study.
Accurate extraction of glacier movement holds special significance in the analysis of the glacier dynamics and mass balance. There is few research of glacier movement with Chinese high-quality remote sensing images in High Mountain Asia. In this paper， based on the SAR imagery of the High Mountain Asia acquired by GF-3 with FSI imaging modes， the distribution of ice surface motion is obtained with GPU parallel algorithm pixel-tracking algorithm from 2019 to 2020. The results demonstrate that the operating efficiency was greatly improved. The accurate ice motion with an accuracy of 0.5 m was extracted by removing the global deformation， the topographic-related offset and the noise. The glacier flow velocity was assessed by the results of quasi-same period Landsat-8 data and the statistical analysis of the residual movement in the non-glacial region， then the usability and applicability of GF-3 data in monitoring glacier motion was evaluated. Because of the high spatial resolution， GF-3 satellite imagery plays a unique advantage in monitoring the glacier motion on the small-sized and slow-moving glaciers， which could better reflect the detailed information of glacier movement and corresponding variation. Furthermore， the accurate extraction of glacier surface movement in Qinghai-Tibet Plateau region would provide better insight into the spatiotemporal evolution of glaciers and global climate change.
The “Digital Heihe River Basin” can be considered as an implementation of the Digital Earth concept in the Heihe River basin， the second largest inland river basin of China. The Digital Heihe River Basin is composed of an information infrastructure and its applications. The former is further built up by a data integration platform， a modeling system and an automatic observing system， and the latter are various applications using integrated models and decision support systems. With the rapid growth of the spatio-temporal data of Heihe River basin， some existing Heihe information service systems have defects in the aspects of sharing efficiency， data analysis and platform architecture， etc.， which can no longer meet the practical needs. In this study， the overall framework of the new digital Heihe information system （NDHRIS） is redesigned to address the defects of the current platform， and the new functions of the new digital Heihe information system are realized from three aspects： observation， data and model. In this paper， the overall design of the system is introduced from three levels： infrastructure， service and application. Secondly， the key technologies and functional improvements of the system are described in detail. Finally， the existing problems and future development directions of the system are discussed. At present， the system has been operational and includes a lot of data with key variables of cold and arid regions in China， such as glacier， snow， frozen soil， desert， model datasets such as surface atmospheric forcing， soil texture， plant functional type map， eco-hydrology remote sensed products， and comprehensive dataset in Heihe River basin. It has a data volume of more than 5 T and a total of 1 058 metadata， providing about 8 TB data sets and 5 000 data services to about 100 research institutes and 50 projects， effectively improving the sharing efficiency of scientific data in Heihe River basin and supporting the implementation of the global cold monitoring plan.
