Climate warming is amplified in the Arctic and accompanied by sea ice decline，which makes it possible for resource exploration and opening new sea channels. The importance of the Arctic region is becoming increasingly prominent. With the aim to understand the most influential research forces and fields in Arctic research，to provide the most comprehensive analysis of scientific research information，and to reveal the existing problems in Chinese current research，408 ESI top papers on Arctic research in the last decade were analyzed，including number of papers，authors，research institutions，countries and research areas. It is found that the United States dominates the Arctic research （number of papers，authors，institutions，funding funds）.The Arctic research fields include sea ice and oceans，organisms and typical ecosystems （adaptation and protection of biodiversity，boreal forests，tundra，microorganisms），glacier retreat and permafrost degradation，atmosphere，weather and climate system and other related fields. A great number of studies characterized by using large data and model operation，but “uncertainty” is common in all the fields. China conducts Arctic research in a cooperative，participatory，periphery-related and micro-entry manner. There are multiple constraints for China to conduct Arctic research. China may take advantage of the existing achievements in cryosphere research，actively participate in all fields of arctic research and data sharing，and focus on the impact of Arctic climate on mid-latitude regions to provide support in hazards prevention and mitigation，and thus improve ecological environment in China as well.

When the Scan Line Corrector(SLC)on Landsat-7 loses efficacy and forms a wedge-shaped data gap in SLC-OFF image,resulting in roughly 22% of the pixel to be missed,and leaving a serious problem for the application of ETM+data on studying glaciers,particularly for monitoring long- term glacial variations in High Asian Mountains,where there is few high quality remote sensing data. In this study,the Siachen Glacier,the largest glacier in the Central Karakoram,was selected as a monitoring site. We aim to evaluate the potential of the Landsat-7 ETM+ SLC-OFF images in deriving surface velocities of mountain glciers. A pair of SLC-OFF images acquired from 2009 and 2010 were used for this purpose. Two typical filling-gap methods,the localized linear histogram match(LLHM)and the weighted liner regression(WLR),were utilized to recover the above mentioned SLC-OFF images. Then the recovered images were applied for deriving glacier surface flow velocities using sub-pixel correlation. The results show that both LLHM and WLR methods can effectively repair the glacier area in the Landsat-7 SLC-OFF images. Besides,the surface flow velocities estimated with the recovered SLCOFF images are highly agreement with those from the Landsat-5 TM images. The accuracy of above three flow velocities are 5.9 m·a^-1,6.3 m·a^-1 and 4.0 m·a^-1,respectively. This study verifies the potential of the Landsat-7 ETM+ SLC-OFF images in deriving surface flow velocities of mountain glaciers.

根据青藏公路和青藏铁路多年的研究实践,对青藏高原多年冻土区路堤的临界高度进行了分析和讨论.在青藏高原多年冻土区,由于各地年平均气温不相同,因而各地空气的融化指数和冻结指数不相同.在同一地区,路堤表面材料特性不同,其表面的融化指数和冻结指数也就不同.如果在某一地区,路堤表面的融化指数和冻结指数相等,则该地路堤的融化深度和冻结深度也应相等(忽略路堤及基底土体融化状态和冻结状态下导热系数的差异).在这种情况下,该路堤临界高度等于路堤融化(冻结)深度减去天然上限埋深,该地区的年平均气温即该路堤临界高度的年平均气温临界值.对于一定表面特性的路堤,当某地区年平均气温高于临界值时,则该地区不存在路堤临界高度;只有当年平均气温低于临界值时,路堤临界高度才存在,且随年平均气温的降低,临界路堤高度减小.在此基础上,提出了无临界路堤高度地区路堤的设计原则,以及保持路堤下多年冻土上限不变的工程措施.

2013年9月27日, 在瑞典首都斯德哥尔摩, 联合国政府间气候变化专门委员会第一工作组第五次评估报告《Climate Change 2013: The Physical Science Basis》决策者摘要(Summary for Policymakers, SPM)发布, 随后于9月30日公布了报告全文. 报告指出, 全球气候系统变暖的事实是毋庸置疑的, 自1950年以来, 气候系统观测到的许多变化是过去几十年甚至近千年以来史无前例的. 全球几乎所有地区都经历了升温过程, 变暖体现在地球表面气温和海洋温度的上升、 海平面的上升、 格陵兰和南极冰盖消融和冰川退缩、 极端气候事件频率的增加等方面. 全球地表持续升温, 1880-2012年全球平均温度已升高0.85 ℃[0.65～1.06 ℃]; 过去30 a, 每10 a地表温度的增暖幅度高于1850年以来的任何时期. 在北半球, 1983—2012年可能是最近1 400 a来气温最高的30 a. 特别是1971-2010年间海洋变暖所吸收热量占地球气候系统热能储量的90%以上, 海洋上层(0～700 m)已经变暖. 与此同时, 1979-2012年北极海冰面积每10 a以3.5%～4.1%的速度减少; 自20世纪80年代初以来, 大多数地区多年冻土层的温度已升高. 全球气候变化是由自然影响因素和人为影响因素共同作用形成的, 但对于1950年以来观测到的变化, 人为因素极有可能是显著和主要的影响因素. 目前, 大气中温室气体浓度持续显著上升, CO₂、 CH₄和N₂O等温室气体的浓度已上升到过去800 ka来的最高水平, 人类使用化石燃料和土地利用变化是温室气体浓度上升的主要原因. 在人为影响因素中, 向大气排放CO₂的长期积累是主要因素, 但非CO₂温室气体的贡献也十分显著. 控制全球升温的目标与控制温室气体排放的目标有关, 但由此推断的长期排放目标和排放空间数值在科学上存在着很大的不确定性.

In this paper, the successful achievements of ice core study are comprehensively reviewed in such aspects as past environmental and climatic changes, abrupt climate changes, solar activity, atmospheric dust content, greenhouse gases, volcanism, biogeochemical cycle, universal events and human influences on environment. Some important issues are discussed, such as the Younger Dryas events, the correlation between climate changes and greenhouse gases, and the phase difference between climate changes in the northern and southern hemispheres. Some new research directions in ice core study are suggested too, for examples, microorganism and environmental geomagnetism.

Using the NCEP reanalysis data,the precipitable water,vapor flux,divergence of vapor flux and stream fields in the South to North Water Transfer areas of western China were analyzed.The results showed that from May to September,the maximum precipitable water was in July,followed by August,and then by June and September.The vapor flux inpoured into the studied area mostly from the south boundary,from the north boundary steadily and weakly and from the west boundary irregularly.Sometimes,there was outflow.The vapor flux at 600 hPa was almost converged,which was mainly caused by the convergence of wind.At the lower levels vapor came directly and indirectly from the Bay of Bengal.At the higher levels it mainly came directly from the Bay of Bengal.

As an important component of global climate system,the Polar sea ice impacts global climate by sea surface radiation balance,mass balance,energy balance,as well as the circulation of sea water temperature and salinity.Sea ice has been studied for a long time.Many correlative sea ice projects were established through extensive international cooperation,from the primary research of strength and bearing capacity of sea ice to the development of sea/ice/air coupled models. Based on these studies,sea ice variations were combined with global climate change.The research fields about sea ice includes: the physical properties and processes of sea ice,together with snow cover,the ecosystem of sea ice regions,albedos of sea ice and its snow cover,mass balance of sea ice regions,sea ice and climate coupled model.A simulation suggests that both the extent and volume of polar sea ice will decrease in the 21st century.With the developing of sea ice researches,more new scientific questions are raised,such as the interaction between sea ice and the other factors of global climate system,the seasonal and regional distributions of Polar sea ice thickness,Polar sea ice boundary and area changing trend,sea ice growth,melt and its influencing factors,the role of the polynya and sea/air interactions.

The climatic characteristics of precipitation and the maximum precipitation in the west course of the South to North Water Transfer were analyzed using the daily precipitation data of thirty meteorological stations from 1965 to 2000.It is revealed that the mean annual precipitation is 520.5 mm.The contour lines of the mean annual precipitation run from northeast to southwest.The diversion from the semi-arid region to humid region runs along Yushu-Qingshuihe-Dawu-Henan-Hezuo-Lintao.Precipitation processes are almost longer than five days;most of them are in three days.According to the shape of precipitation,the precipitation process could be classified as two categories.One is latitudinal,and the other is diagonal.The latter has a larger percentage,with northwest-southeast and northeast-southwest shapes.The center of precipitation often moved from northwest to southeast.Sometimes the center moved a little,but the rain area is large and then gradually shrinking.The 1-day maximum precipitation occurs mostly in Rangtang,following in Ruoergai and Lintao.The 3-day maximum precipitation occurs mostly in Lintao,following in Zoig? and Rangtang.The extreme values of the 18 precipitation processes are distributed similarly to the extreme values of mean annual precipitation.For the eight high water years,the precipitation processes in 1984 and 1992 were weaker and those in 1981,1989 and 1999 were stronger.

Harbin-Dalian High-Speed Railway, crossing Northeast China, is the first new-built and operating high-speed railway in cold regions around the world. The subgrades of the railway were treated with filling material replacement and taking waterproof measures and so on to prevent frost damages. For evaluating the effects of the frost heaving prevention and engineering operation status of the subgrades, the monitoring data during the first freeze-thaw period (2012-2013) from 9,641 monitoring points along the railway were analyzed. The occurrence, development and changing of the frost heaving were summarized. It is found that the development of the frost heaving includes the rapid growing stage, the stable frost heaving stage and the thawing settlement stage. The frost heaving deformation occurs along the whole line, but the frost heaving amount, great or small, is under control. The frost heaving degrees are related to the subgrade structures. The frost heaving occurs mainly in shallow part of a subgrade base, and its damage degree depends on the subgrade structure. On the whole, the frost heaving in the transition section is slight, followed by that in the embankments, and it is most serious in the cutting sections or in the base-plate jointing parts. As engineering treatments against frost heaving, it is suggested to focus on reducing surface water infiltration and control frost heaving deformation of the subgrade base. And in the designing of high-speed railway in seasonal frozen soil regions, bridges are strongly recommended instead of subgrade, and to modify the upper layer of the subgrade to no frost heaving structure.

As an emerging space technology in geodesy， synthetic aperture radar interferometry （InSAR） has the advantages of all-day， high-precision， large range and fast speed. It has a great potential for application in surface deformation measurement， and is increasingly used in the monitoring of permafrost areas. In this paper， the principle of permafrost deformation and the application of InSAR to monitor permafrost deformation are reviewed. The results show that the interannual deformation of the permafrost is mainly settlement in the context of climate warming， and the amount of underground ice near the upper limit of permafrost is the main factor affecting the interannual variation. Soil moisture content within the active layer affects the magnitude of the seasonal deformation variables. There are large differences in interannual and seasonal surface deformation variables for different types of permafrost areas. It was also shown that the applicability of SAR products at different wavelengths varies for different types of permafrost zones， and that subsurface features have a greater influence on the magnitude of deformation obtained by InSAR data， while the L-band SAR data are more effective in the areas with better vegetation cover. Owing to the decoherence problem of InSAR processing and the lack of validation and calibration data for long-term， multi-type， high-frequency permafrost deformation monitoring， it is of great practical and scientific significance to establish surface deformation inversion algorithms for different permafrost areas and to construct surface deformation data sets with high precision spatial and temporal resolution.

In 2012 a serious drought happened in China. In this paper, combined with the latest state surface soil and hydrological parameters, using the soil volumetric water content products of CMA Land Data Assimilation System (CLDAS-V1.0), published in November of 2013, relative soil moisture in China in 2012 was calculated. Then, agricultural drought can be monitored based on the state standard of Agricultural Climate Center of China. The result shows that it can reflect the change of drought in all years, especially in Southwest Chia, South China, Northeast China and the Huanghuai and Jianghuai plains. It is believe that a temporal-spatial continuous real-time product can be made out to monitor the drought and to support agriculture development in China.

Glacier mass balance is regarded as the bridge and tie between the meteorology and water resources in glaciated regions, so monitoring and simulating mass balance is always one of the frontier research topics. A physical energy-balance model and four statistical degree-day factor models based upon temperature-index, radiation-index and temperature-radiation-vapor-index are presented, in which the Shiyi Glacier is taken as a case of study. The results are deeply analyzed and evaluated. When the degree-day factor model is enhanced by net shortwave radiation index, resulting in 90% of the ablation rate, the model will be improved significantly. The enhanced day-degree factor model combining with shortwave radiation and water vapor becomes the best model amongst all models. The results of energy/mass balance models suggest that net radiation is the dominant energy source to the glacier surface, accounting for 82.3% of all the inward fluxes, followed by the sensible heat flux, accounting for 17.7%of all the inward fluxes. The long wave radiation is mostly negative one during the modeling period. The ablation energy and latent heat flux account for 84.7% and 15.3% of the heat loss. The relative error of the radiation-vapor day-degree model is 7%, which is slightly higher than that in energy-balance model, 6.7%. Comparison suggests that the energy-balance model is more capable of modeling the value and the amplitude of variation, especially in daily scale. Likewise the statistical models perform insufficiently, especially, to the local specific topography. However, the statistical models require few input data, with computational simplicity. This study will be useful for establishing glacier mass-balance model in the Heihe River Basin and the Qilian Mountains.

Under the background of global warming and continuous degradation of permafrost， retrogressive thaw slumps are widespread in the permafrost region of the Qinghai-Tibet Plateau （QTP）， which not only affects the regional ecological environment， but also influences the stability of engineering structures. Based on field investigations， remote sensing interpretation and meteorological data， the triggering factors， distribution characteristics and evolution process of retrogressive thaw slumps in permafrost region of the QTP were analyzed this paper. Results showed that the occurrence of active layer detachment is the main factor that induce the retrogressive thaw slumps in permafrost region of the QTP， followed by the engineering disturbance and the thermal erosion of lake water. The development process of retrogressive thaw slumps which induced by active layer detachment mainly includes three stages， they are the occurrence of active layer detachment， the collapse and retreat of the headwall and the formation of slope mudflow. The source erosion after the formation of retrogressive thaw slump will last for several years or even more than ten years until the content of ground-ice in the back edge is significantly reduced or disappeared. In terms of spatial distribution， retrogressive thaw slumps tend to be distributed on the side of the shady slope in the hilly and piedmont regions with gentle slope （3°~8°）. In addition， the retrogressive thaw slumps in permafrost region of the QTP had significantly increased in recent years， and such intensification of retrogressive thaw slumps did not increase steadily over the study period but was rather concentrated during the special years with extreme high air temperature. The research results will provide references for the future engineering planning， resource development and environmental protection on the QTP.

With the population growth and the economic and social development， the contradiction between supply and demand of water resources is on the increase day by day. It is a crucial new task to save， protect， manage， rationally develop， efficiently utilize and optimize allocation of water resources comprehensively. As an important way to study the sustainable utilization of water resources， entropy weight method can eliminate small contribution to the evaluation results in the index system of indicators， reduce the influence of human factors on the subjective weight， and thus more accurate calculation results are achievable， which can objectively reflect the status quo of water resources and water environment. For this reason， the method is widely used in the evaluation of water resources and water environment， which will provide scientific basis for efficient utilization of water resources and comprehensive evaluation of water environment. This article explored the origin of the entropy weight method and development process in the evaluation of water resources and environment， discussed and summarized the four applications of the entropy weight method in water resources quantity， water resources carrying capacity， water environmental quality and water ecological environment assessment and found the entropy weight method shows a good application prospect in the evaluation of water resources and water environment. Meanwhile， in view of the shortcomings of entropy weight method in water resources and water environment assessment， some improvements are suggested， which will provide new ideas for the research direction of water resources and water environment assessment. In addition， the future of entropy weight method is forecasted： by combining the entropy weight method with other methods innovatively， a reasonable and comprehensive evaluation index system can be built， and applied in the development trend of water resources utilization and spatio-temporal pattern evolution.

The freezing-thawing process and the dynamics of soil moisture were analyzed with the measured data of temperature and moisture within the active layer at the Cryosphere Research Station on Qinghai-Xizang Plateau from September 1, 2007 to September 1, 2008. Both freezing and thawing processes within the active layer developed from the surface to permafrost table. The freezing duration of soil within entire active layer was 25 days, while the thawing duration was nearly 4 months, The freezing process took much less time than the thawing process. The duration of the diurnal freezing-thawing cycles of topsoil decreased with depth. Frequent diurnal freezing-thawing cycles brought a daily cycle of soil water phase changing, which made the topsoil releasing and absorbing latent heat of phase change, changing the soil hydraulic and thermal properties. The migration of soil moisture had different characteristics at different stages of the freezing-thawing cycle. In general, during a freezing-thawing cycle, the soil water molecules will migrate downwards, i.e., soil moisture will transport from the entire active layer to the upper limit of permafrost. In the meantime, the content and migration of soil water have a significant impact on the seasonally freezing and thawing process within the active layer.

科研人员在人生演进的方向上是否存在共同的"道", 针对这一问题笔者介绍了自己在程国栋先生带领下修炼得到的体会. 首先, 是与先生17年"因缘和合"中对"风行水上涣"的诠释;其次, 阐述的是自己从先生快哉雄风中听出的科研人员之"道": 成其大—养浩然之气. 具体为: 一要有十年铸一剑的精神(阳), 二要有江海纳百川的气度(阴). 阐述了科研人员求道的要点, 将其分为十年铸一剑、正确应对妖魔鬼怪、防止走火入魔、打掉魔头四个阶段进行了阐述;同时介绍了自己求"道"的几点体会. 最后, 讨论了对读书的理解以及拟采用的生态经济小组建设模式. 这些阐释对科研人员个人的发展具有重要的指导意义.

The 3-point bending tests were carried out on the frozen soil samples with different sizes so as to investigate the effect of sample size on the fracture toughness K_Ic of frozen soils. The effect coeficient α was obtained from the test results according to Weibull′s statistical theory of brittle failure, which was used to predict the theoretical values of K_Ic for the frozen soil samples. Comparisons between the theoretically calculated and measrued values of K_Ic indicated that the maximum error is less that 5%.

Due to the influences of complex mountainous topography, the spatial-temporal characteristics of water and energy fluxes in a mountainous river basin are often dramatically changed. In this paper, a macro scale hydrologic model, the variable infiltration capacity (VIC) model, was used to simulate the spatial-temporal distribution of water and energy fluxes in the upper reaches of the Heihe River. The simulated results were validated with in-situ observations. It was showed that the VIC model is able to properly simulate the outlet discharge and net solar radiation, while it could only represent the changing trends of other variables, such as sensible heat flux, latent heat flux and ground heat flux. The simulated snow process differed from observations, leading to underestimation of outlet runoff, a sudden rise in soil moisture around April and a discrepancy in energy fluxes simulation. The VIC model has a good simulation of soil moisture in summer (from June to September), but bad in other months in which snow melting and soil thawing/freezing processes occur. Snow melting while top soil thawing will jointly induce a sudden rise in soil moisture, and top soil freezing will induce a fast drop in soil moisture. Overall, the VIC model is capable of simulating the spatial-temporal distribution of water and energy fluxes in mountainous basins with spaces to be improved where snow melt and soil thawing/freezing take place.

Soil thermal conductivity plays an important role in the transmission of surface soil heat into underlying soil, and also is a key parameter in the regional climate model or land surface model. In this paper, an overview of advances on soil thermal conductivity is tried to provide, and its impact factors and schemes are introduced. The thermal conductivity is significantly affected by soil texture, temperature, moisture and soil porosity, and what's more, the research of frozen soil needs to focus on the change of ice content. Then the parametric processes and the advantages and disadvantages of various models are also analyzed. However, these schemes are mostly used in simulating thermal conductivity under normal temperature, which are difficult to be applied in research of frozen soils in the Tibetan Plateau. For researching the frozen soils in the plateau, observation data or parameterized scheme of the land surface model is necessary. Due to the impact of soil freezing and thawing cycles, the thermal conductivity in the plateau still needs to be further studied.

A study of carbon (C) storage in the range of 0～0.75 m deep of soils of various grasslands on the Tibetan Plateau was carried out. It is found that there are 1.627 million km² of grasslands in the plateau, where organic carbon content reaches 33.52 Pg of C. Organic carbon is mainly stored in meadow and steppe soils, reaching 23.2 Pg of C. stored in organic form. This accounts for 23.44% of China s total organic soil stored carbon or 2.5% of the global soil carbon pool. Carbon emission from the grasslands was estimated, based on the two major modes of emission: (i) natural soil respiration and (ii) shifts in net C flux to/from soil due to land use change and their potential influence on organic matter decomposition. CO₂ emission from the grasslands of the plateau driven by annual soil respiration reaches 1.17 Pg·a^-1 of C, accounting for 26.4% of China s total soil respiration or 1.73% of global soil respiration. Because the grasslands is accounted for 1.02% of the global terrestrial area or 16.9% of China s total terrestrial area, this CO₂ emission rate is significantly higher than the mean annual rate of China (about 4.2 Pg·a^-1 of C ), and even higher than the global mean rate (about 68 Pg·a^-1 of C). In the last 30 years, about 3.02 Pg of C have been emitted from the grasslands of the plateau due to change in land use and grassland degradation. The total CO₂ emission rate from the grasslands of the plateau reaches 1.27 Pg·a^-1 of C. Protecting grasslands on the plateau is of great importance for limiting global climate change.

The Bering Sea is a marginal sea of the Arctic Ocean， and its sea ice changes differ considerably from other marginal seas. The sea ice area （SIA） in the Bering Sea has shrunk significantly over the last decade， affecting regional hydrology， the atmosphere， and even the ecosystem， as well as the mid-latitude and our national climate systems. Lots of efforts have been conducted in the temporal and spatial characteristics of sea ice based on satellite observation， simulation， diagnostic analyses， and so on. The recent changes in sea ice in the Bering Sea are proposed， as well as the impact factors of sea ice changes. Simultaneously， the effects of Bering Sea ice changes on hydrology， atmosphere， ecosystems， and the mid-latitude climate system are summarized. According to a comprehensive review of current studies， the understanding of the mechanism of sea ice change on an intraseasonal time scale is still insufficient due to the limitation of current study approaches and observation data on seawater current， as well as a lack of systematic analysis to explore the causal relationship. It is also stated that more research on the impact of early sea ice on later sea ice， the drag effect of wind field on sea ice， the time scale of the effect of warm advection on sea ice， and the time-scale evolution of sea ice change is required.

Xinjiang is the largest area of glaciers and snow cover resources in China. Glaciers and snow melt water plays an important role in water resources. The hydrological processes of the rivers have been changed by the responses of glaciers and snow cover to climate change during last 50 years. The runoff of mountain areas occupies over 80% of the total surface runoff, and the proportion of glaciers and snow melt water is up to 45% or more. The rivers in the Altai Mountains in the northern of Xinjiang and in the north slope of the Tianshan Mountains were mainly dominated by snowmelt runoff. The rivers are located in the southern slope of Tianshan, Kunlun Mountains, Karakorum Mountains and the Ili River Basin was supplied mainly by glaciers melt water. The flood season of the river supplied by snowmelt is in the spring to early summer, and which of the supplied by glacial melt water is in summer. With the transform of the climate changes to warm and humid in Xinjiang, the hydrological processes of alpine basin had presented some significant responses to the climate warming and the snow cover increased: the maximum runoff month advanced in the rivers supplied by snow cover, and the runoff decreased obviously in summer; the runoff in June to September increased significantly in the river supplied by glacier melt, and the runoff in flood season increased, and the annual runoff increased. The changes of the hydrological process in different types of river have had a significant impact on water supply and flood safety management in the lower reaches of rivers. So it is necessary to adjust the strategies of the water resources management in order to adapt the effects of climate change on hydrological processes, and mitigate the effects of climate change on water safety.

The interaction between permafrost and atmosphere is mainly accomplished through the thermal and hydro-dynamics in the active layer. In background of climate change， the simulation of freezing-thawing process， active layer thickness map and variation-prediction are the basis of studying ecological environment， hydrology， engineering and carbon cycle of permafrost regions. For this paper， we summarize the application of different revised Stefan equations in simulating freezing-thawing process and active layer thickness， as well as its significant application in multi-layer soil， and then discuss the possible questions in its implication. Stefan equation revealed the linkage between change of surface temperature （or air temperature） and freezing-thawing process of ice （or soil） in a simple form， which significantly simplified the analysis and calculation of freezing-thawing process of soil. Stefan equation， with less parameters， simple form and reliable simulation results， is widely used to simulate freezing-thawing process. Also， more and more studies focusing on coupled it to climate model， land surface model and hydrological model. Stefan equation was originally proposed in the study of lake ice formation in the Arctic region and later widely used in permafrost. It was improved by considering soil water content， difference between ground and air temperature on different underlying， topography， precipitation and other factors， and even was applied to simulate freezing-thawing process of heterogeneous soil. However， on the Qinghai-Tibet Plateau， Stefan equation is widely used for simulating spatial distribution of active layer thickness of permafrost for homogeneous soil but rarely applied to heterogeneous soils. Therefore， it is necessary to further study that Stefan equation simulated freezing-thawing process for multilayer soil in the future， which will provide a basic method for accurately studying the response of permafrost to climate change.

Based on the measured and surveyed hydrologic data of the Shule River basin, Hexi Corridor from 1956 to 2013, monthly and annual variations of mountain runoffs of the trunk streams of the Shule River were statistically analyzed, and Kandel rank correlation method was used to inspect runoff variation in the basin. The results show that the mountain runoff averaged over 1956-2013 is 11.6679×10⁸ m³; floods concentrate from June to September, when the runoff accounts for 35.9%~78.7% of the annual runoff; groundwater recharge accounts for 40.46% of the runoff on the average; annual variation of the mountain runoff is continuously increasing with a relatively small rate. It is predicted that in the next 5 years (2014-2018) the annual average mountain runoff of the trunk streams of the Shule River would increase to 13.01×10⁸ m³.

Based on the former research results and latest investigation materials, this paper summarizes the research process and existing problems about desert lakes and megadunes and further exploring the supplying resource and mode of the lakes in the Badain Jaran Desert. It comes to a conclusion that the supplying source of both desert lakes and underground water is neither by local precipitation or flood resulting from precipitation on the peripheral Jacob Lai mountains-North mountains, but rather feed by southern Tibet Plateau including Qilian Mountain through atmospheric precipitation, ice thawing and far-source plateau lakes feeding. The supplying mode is the infiltration water rich in CO₂ and CaCO₃ goes through the raptured pipe which forms underground circulation system. It delivers the water continuously from south to the north, desert zone. When the groundwater arriving at the desert lake zone, it will be heated up by the vertical conductive structure shaped like "laid tile" arc which is made from magmatic rock. Then the water overflows from the faults to form lake group, meanwhile it leads to the release of CO₂ and CaCO₃ deposition forming calcium cementation layer. The mechanism of formation of megadunes is that when underground water in deep depth goes upwards to feed the desert covered zone the drum shaped desert underground water is formed beneath artesian head and above the artesian head, water vapor keeps going upwards and stays at the surface of sand particles and the uncoagulated hot vapor continues going upwards and is absorbed by sand particles of new deposited sand to form wet sand receiving renewed sand particles deposition. Thus the circulation repeating leads to the growth of sand dune and finally the megadunes are formed.

In recent years, there is a warm and wet tendency over the Tibetan Plateau, as a result, the lake levels extensively rise up and dike burst happens occasionally. In this study, the TM(ETM+)history document data and environmental mitigation satellite(HJ-1A/B)CCD data in the Zonag Lakes(including Kusai Lake, Hedin Noel Lake and Yanhu Lake), combined with the air temperature, precipitation data from Wudaoliang Meteorological Station, were used to analyze the variation of lake surface area. The results showed that from 1961 to 2012, precipitation had increased in Hoh Xil, which was the basis of the Zonag Lake outburst. Two strong precipitation processes occurred before August 22, 2011 and then followed by a continuous precipitation, which led to a substantial leakage of the lakes, and finally led to outburst. There were two earthquake events before the dike burst, which may have a certain influence on the basin structure of the lakes, accelerating the dike burst process. Outburst of the lake led to shoreline retreat and land desertification, which deteriorated the Tibetan antelope farrowing environment and resulted in adverse impact on the surrounding grassland ecology environment and major engineering projects.

The Working Group I report of the Sixth Assessment Report （AR6） of the Intergovernmental Panel on Climate Change （IPCC） was released in August 2021. Base on updated and expanding data， AR6 presented the improved assessment of past changes and processes of cryosphere. AR6 also predicted the future changes using the models in CMIP6. The components of cryosphere were rapid shrinking under climate warming in the last decade. There were decreasing trends in Arctic sea-ice area and thickness. Sea-ice loss was significant. The Greenland Ice Sheet， the Antarctic Ice Sheet and all glaciers lost more mass than in any other decade. Global warming over the last decades had led to widespread permafrost warming， active layer thickness increasing and subsea permafrost extent reducing. Snow cover extent in the Northern Hemisphere also decreased significantly. However， the variations of snow depth and snow water equivalent showed great spatial heterogeneity. The rapid shrinking of the cryosphere accelerated the global mean sea level rise. The impact of human activities on cryosphere will become more significant in the future. The Arctic sea-ice area will decrease， and the Arctic Ocean will likely become practically sea ice-free. The Greenland Ice Sheet， the Antarctic Ice Sheet and glaciers will continue to lose mass throughout this century. Permafrost and Northern Hemisphere snow cover extent will continue to decrease as global climate continues to warm. In addition， there are still uncertainties in the prediction of cryosphere due to the absence of observations， the poor sensitivity of models to the components and processes of cryosphere， and the inexplicit represent of the mechanism of light-absorbing impurities. More attentions should be paid on these issues in the future.

Based on the data of ground temperature and deformation beneath embankment of the Qinghai-Tibet Railway in permafrost regions from 2006 to 2013, characteristics of thawed interlayer beneath embankment and its effect on the embankment settlement deformation are studied. The results indicate that there is a little thawed interlayers beneath the original field along the Qinghai-Tibet Railway. However, beneath the embankment the thawed interlayer develops widely, while it can be refrozen totally in the regions of lower annual mean ground temperature and developed further in the regions of higher annual mean ground temperature. Thawed interlayer is closely related to the embankment settlement deformation. The ice content of permafrost under the thawed interlayer controls the settlement deformation of the embankment; the higher the ice content is, the more the settlement deformation is.

Freezing-thawing is a kind of weathering process, which considerably changes structures of soil. Change in soil pore structures has given expression to change in structure characteristics. In order to study the influence of freezing-thawing cycles on pore structures, specimens of silty clay from the Tibetan Plateau were prepared for tests under freezing-thawing cycles, 50 at most. Mercury intrusion porosimetry (MIP) is used to obtain pore size distribution and pore fractal dimension. A bimodal pattern is found the log-differential curves, which indicates that two different mechanisms are involved in forming the pores within the material. Freezing-thawing cycles have less impact on pores of small size, because of the pore size and pore volume almost remaining unchanged. However, pores of large size (especially the pore size at 20-40 μm) are influenced greatly by freezing-thawing cycles for the pore size and pore volume greatly increased. There is no obvious relation between soil porosity and freezing-thawing cycles. However, the overall changing trend of the soil porosity is first increasing and then decreasing. According to a pore fractal dimension calculation, freezing-thawing cycles change the pore structures, resulting in decrease in pore wall roughness and pore structure complexity.

Glacier and snow cover distributed widely in Xinjiang, when its melt water supply to the rivers often accompanied by glacial floods, snowmelt floods, glacial lake outburst floods, glacial debris, ice and snow avalanches, snowdrift and other snow disasters. There are greater threats on the local urban residence and the important defense lines because of these disasters. The extent and range of the ice and snow disasters impact subjected to the changes of glacier and snow cover. The glacier flood and glacial lake outburst floods occurred mainly in the Karakoram Mountains, Kunlun Mountains and the western of the southern slope of the Tianshan Mountains in the Tarim River Basin. The snowmelt floods occurred mainly in Altay area, Tacheng area and the northern slope of the Tianshan Mountains in North Xinjiang. The glacier debris and the ice and snow avalanches disasters occurred mainly in the Pamirs Plateau, the western of the Tianshan Mountains, the Karakorum and the West Kunlun Mountains. The snowdrift occurred mainly in the middle and western of the Tianshan Mountains regions. With global warming, especially the beginning of the climate change from warm-dry to warm-wet in 1987 in Xinjiang, the glacier retreat intensified, the melt water increases, the glacier floods and debris flows increased with the increased of glacier melt water, and the snowmelt floods, ice and snow avalanches and snowdrift enhanced with the snow cover increased in winter and the air temperature rise, the alpine ice disintegration caused by ice avalanches with climate warming showed an increasing trend. The ice and snow disasters dominated by the glacier and snow floods in Xinjiang. The increasing trend of the frequency and intensity of glacier and snow floods under the influence of climate change have been observed in the last decade in the Xinjiang region. The water safety and disasters and other problems caused by glacial lake outburst floods and glacial floods in the Tarim Basin and the ice and snowmelt floods in spring in North Xinjiang have become increasingly prominent, and have great harm on the local lives, property and socio-economic development. With the glacier melt water increasing, some new disaster may be formed in the future. For the numerous glaciers, snow disaster induced by the climate change, there is a lack of adaptation on disaster monitoring, forecasting and early warning. So it should be keep an eye on the ice and snow disasters with the global climate change accelerating consistently, and to strengthen the study of the impact assessment and adaptation strategies of the disasters, and make the science and technology play a leading role in disaster reduction.

Glacier flow transports the mass obtained in the accumulation area to the ablation area， and controls the length， area， mass balance and thickness of a glacier， which is the key factor to control the advance and retreat of a glacier. In recent years， with the climate change， most of the glaciers in the world are retreating， but a glacier flow variation is more complex， which has attracted extensive attention of scholars. This paper systematically summarizes the extraction methods of glacier flow velocity， research progress on spatial distribution and change of glacier flow velocity， as well as its change with time and influencing factors in recent years， together with discussing the problems existing in the current glacier flow velocity research and the future development trend. The results show that the method based on the stakes can obtain the data with high accuracy， but it has limitations in time and space. At present， the method of automatic extracts glacier flow velocity based on remote sensing data has been widely used. However， the registration of images and the calculation of massive data are the main problems restricting the research of glacier flow velocity at the current stage. In recent years， unmanned aerial vehicles and ground-based synthetic aperture radar are increasingly applied to study on glaciology， providing high-precision data support for glacier flow velocity studies， but not widely enough. The spatial distribution of glacier flow velocity and its variation with time are different from space to space. The current results suggest that the change in thickness of glaciers is probably the main cause of flow velocity change in most glaciers around the world. However， the changes of glacier flow velocity are more complex on a single glacier system， and the reasons need further discussion. With the remote sensing data increasing and cloud computing platforms using， popularity of new technologies such as the Internet of things， unmanned aerial vehicles and ground-based synthetic aperture radar， as well as the emergence of coordinated satellite， air and earth observations， the study of glacier flow velocity will greatly promote in the future. In addition， the mechanism of glacier flow velocity and its dynamic process should be pay more attention to， as a hot topic in the future research of glaciology.

Some problems of embankments, such as salt expansion, frost boiling, frozen heaving, eluviation and saturated yielding, seriously affect the stability and durability of roadbeds in saline soil regions. Considering the problems of the operated roadbeds and the importance of the proposed railway projects, the common methods of stabilizing saline soil are summarized. It is revealed that soil curing agents are developing from single and conventional ones to ionic polymers and then to the new polymer composite materials. From the chemical point of view, the stabilization mechanism of saline soil is discussed, and the microscopic mechanisms of stabilizing saline soil and physical and mechanical properties of saline soil are analyzed. On this basis, the prospect of stabilizing saline soil is reviewed, a variety of methods to comprehensively stabilize embankments of saline soil are proposed.

The water cycle occurs on a global scale， and solutions to local and watershed water problems also often require a global perspective. Therefore， global hydrological models （GHMs） are emerging and fast-growing as a separate research field in the last two decades. In this review paper， we discuss the research significance and great potential of global hydrological modelling and observation， systematically summarize the status of the existing global hydrological models， analyze the main shortcomings and challenges of existing global hydrological models， in order to further improve the models， outlook the trend and momentum of global hydrological model development， in terms of model mechanism， big data， new technology， and the coupling of multi-sectoral models.

As one of the hottest problems in the global change studies,the coupling study of hydrological models and land-surface models has become more and more attractive recently.It has been an important scientific issue how to carry out the intercoupling between distributed hydrological models and land-surface process models,and then embed the two models into the climate models properly in the future GCM or RCM research.After briefly introducing the development of land-surface process models and hydrological models,this paper summarizes the new advances of the intercoupling between hydrological models and land-surface process models and points out the common weakness of all the studies and the research focuses in the future.Finally,it is discussed what kind of role the intercoupling between distributed hydrological models and land-surface models plays in the frame of global change research.At the same time,the main study trends of land-surface hydrological process are also proposed.

The snow and ice albedo plays a key role in the energy balance between the earth and atmosphere.Its variation depends up two aspects,i.e.the reflecting properties of snow/ice and the sky conditions.So,many factors affect the snow and ice albedo,such as physical properties of snow and ice,including grain size,density,water content,impurity and so on.Again,cloud affects the albedo,because it changes the incoming solar radiation and its spectral distribution.In view of the changes in reflecting properties of snow/ice and the sky conditions,the albedo of snow and ice exhibits its diurnal,seasonal and spatial variations.The progress of numerical model and satellite remote sensing in snow/ice albedo are also reviewed in this article,especially focused on the Bidirectional Reflectance Distribution Function(BRDF)and the imperfection of albedo inversion in remote sensing.

The ecological protection and management of Qilian Mountains has always been the focus of national, local government and local residents. How to ensure water security and ecological stability in the region are the top priority of current work. This paper points out the existing problems and challenges in the ecological environment protection and restoration of the Qilian Mountains. In view of these problems, this paper puts forward the following suggestions: strengthen the management system mechanism, establish the comprehensive ecological monitoring system, carry out the Ecological Red Line delineation study, speed up the improvement of ecological compensation mechanism, and strengthen the application of ecological restoration technology demonstration recommendations, so that promotes the progess of Gansu Province in ecological protection and management of Qilian Mountains.

Snow avalanches are a major natural hazard in the cryosphere. It seriously threatens transportation corridors， energy transmission and communication lines， mining and touristic areas in the cold mountainous regions and often causes the destruction of infrastructure and human casualties， hindering the sustainable development of society and economy in mountainous areas. Under climate change and the expansion of human activities to alpine mountains， more population and infrastructure will expose to the risk of avalanches. In order to ensure the sustainable development in mountainous areas， the demand for the prevention and management of avalanche disasters is increasing. Based on the review of the main avalanche research progress in China since 1960 and the avalanche research results all over the world， this paper summarized the progress on the influencing factors and regional distribution of avalanche activities， avalanche formation and movement mechanism， avalanche monitoring and early warning， avalanche risk assessment and engineering prevention， as well as the frontier problems and scientific difficulties that need to be studied. In addition， the impact of climate change on avalanche activities and the interaction between human activities and avalanche activities are discussed. By looking forward to the future needs of avalanche disaster prevention and reduction， including the countermeasures， the research on avalanche in China is promoted.

From the available data of eco-environmental geology and desertification due to permafrost degradation in the source regions of the Yellow River, it is found that the eco-environment is deteriorating in permafrost regions. Permafrost degradation results in lowering or disappearing of the level of groundwater in the seasonal thawing layer, on which the growth of alpine meadow in cold regions depends. Thus, the alpine meadow in cold regions is degrading, together with water environment aggravating. It is the main reason that the alpine meadow, which holds the balance in the source regions of the Yellow River, is losing water and going to desertification.

The precipitation dataset for global land from 1900 to 1998 presented by Dr. Mike Hulme (Climate Research Unit, East Angles University, UK) is the longest global precipitation dataset available now. The evolutional trends of precipitation were studied by using the long historical data in the 20 th century in Northwest China. It is found that the mean precipitation appeared a downward trend from the beginning of the 20 th Century, but a slight upward trend appeared in the end of the 20 th Century. The interannual trends of precipitation between the East and the West showed a contrary variation. In the end of the 20 th century, the mean precipitation appeared an obviously upward trend in the central and western portions of Northwest China, but in the east the mean precipitation continuously decreased, many drought events have happened.