Abstract: Snow storage is one of the effective measures to solve the problems caused by climate warming, such as shorter operation time of ski resorts, higher snow production cost and lack of snow guarantee for large-scale sports events. However, there is a shortage of research on snow storage technology based on efficient thermal insulation structures and new materials, which cannot meet the increasing demand for skiing events and entertainment. In order to select the optimal technical scheme for snow storage, four snow storage banks with comparable construction costs were set up in Wanlong Ski Resort in Chongli District, Zhangjiakou City, Hebei Province, based on different thermal insulation materials and thermal insulation structures. The results show that: from the outside, inside and inside of the main heat insulation structures to the snow surface, the temperature fluctuation decreases gradually, and the difference of heat insulation performance of different heat insulation structures is gradually. Among the four snow banks, the vacuum interlayer in snow bank had the best thermal insulation effect, followed by the thick layer polyurethane snow bank, the multi-layer hollow snow bank, and the vacuum insulating plate had the worst thermal insulation effect. According to the test results, it is recommended to use vacuum sandwich insulation structures and thick insulation material for snow storage.

Abstract: Research of water cycle and runoff variation has always been a difficult issue of assessment of water resources in arid basins. In May and August, 2019, samples of river water and groundwater had taken, then ²²²Rn concentration of these samples were measured and river runoff were also gauged. Then spatial and temporal characteristics of ²²²Rn concentrations in river water and groundwater had analyzed, together with interactions between them. The results show that (1) ²²²Rn concentration of river water in mountains are high, with a mean value of 948.72 Bq·m^-3, indicating that groundwater coming out of bedrock fissure water is an important source of river water in the mountains, especially near a tectonic faults; (2) ²²²Rn concentration of river water in the alluvial floodplain with less groundwater recharge are low, 76.71 Bq·m^-3 in average; (3) ²²²Rn concentration rises to average 676 Bq·m^-3 in the transitional zone of alluvial floodplain and low-lying plain, where groundwater recharges to the river as spring. Toward downstream low plain, ²²²Rn concentration of river water go down again; (4) temporally, compared to May, ²²²Rn concentration of river water is relatively low in August, showing a decline of groundwater recharge; (5) ²²²Rn concentration of groundwater is 2-3 orders of magnitude higher than river water and demonstrate a spatial variation of high in the middle whereas low in the east and west; (6) in S1~S2, two concurrent processes of groundwater discharging to river and river water leaking to groundwater dominate the surface-groundwater interaction. A mass balance method was used to calculate the exchange flux which indicates accumulated river leakage flux in May and August is 3.87 m³·s^-1 and 0.9 m³·s^-1, separately, while 0.51 m³·s^-1 and 0.47 m³·s^-1 for groundwater discharge flux. River leakage is more powerful than river discharge and the flow flux between surface and groundwater varies noticeably in different sections and different time.

Abstract: The Irtysh River originates from the southern slope of the Altai Mountains in Xinjiang, China, and is the only river in China that flows into the Arctic Ocean. With the "Ice Silk Road" proposed by China and Russia, the navigation of the Irtysh River is of great significance, and it is particularly necessary to monitor the changes of its river ice phenology. Based on the second band data of MOD09GQ from 2001 to 2018, this paper analyzes the annual river ice phenology information of the Irtysh River from Burqin to Lake Zaisan, including the beginning time of river freezing, the end time of river ice breaking, the maximum coverage time of ice/snow, the duration of river ice period, the freezing rate and the breaking rate. The results show that: (1) the reflectivity of MOD09GQ gradually decreases with the opening of the river ice. Compared with the observed duration of the river ice period at Nan Wan Hydrological Station, the obtained duration of the river ice period coincides with the observed duration of the river ice period, and has an extended trend. This shows that MOD09GQ can effectively monitor river ice phenology information. 2) The beginning of river closure and the end of river closure both showed an early trend. The beginning of river closure was 45 days earlier than the end of river closure, and the end of river closure was 31 days earlier than the end of river closure. (3) The closure rate tends to slow down and the opening rate tends to accelerate gradually, which means that if the river reaches are navigable in the future, the annual navigation period will be extended. Bring greater economic benefits.

Abstract: There are few studies on the influence of the freeze-thaw cycle on surface energy in the permafrost region of the Qinghai-Tibet plateau. Based on the measured data of Tanggula permafrost, to divides each stage of the freeze-thaw cycle of the active layer according to the 10 cm soil temperature. Combine with surface energy closure and surface energy fluxes to discuss the influence between freeze-thaw cycle of active layer and water-heat exchange. The results show that: each stage of the freeze-thaw cycle of the active layer is affected by climate change. The starting time of the thawing process is advancing and the starting time of the freezing process is delayed. As a result, the duration of soil complete thawing increases and gradually approaches that of complete freezing; in different freeze-thaw states of shallow soil, the energy closure rate different is large, and the energy closure in the stage of complete thawing is generally better than that in the stage of complete freezing; The net radiation value in the stage of complete melting is higher than that in the stage of complete freezing, sensible heat flux dominates in the stage of complete freezing, latent heat flux dominates in the stage of complete melting, and surface soil heat flux is positive in the stage of complete melting and negative in the stage of complete freezing.

Frost heave has a great influence on construction and projects in cold regions. This phenomenon is closely related to process of its thermodynamics, which involving the mechanisms of phase change process between water and ice, ice segregation and water migration. Especially, frozen fringe becomes a key factor to understand the mechanisms of frost heave，which as the water supply station of ice segregation, the region of ice and water phase change and the path of water migration. However, the mechanism study of frozen fringe has currently become a significant challenge. Herein, a detailed review is given about the phenomena, mechanisms, microstructures, characteristic parameters and models of the frozen fringe. For further research of frost heave, it is urgent to continue to strengthen the experimental study, to develop a new test technique to observe the microstructures of the frozen fringe, and to build better a model with the change of characteristic parameters. Study of frozen fringe is reliable to provide theoretical support for analyzing frost heave mechanisms and accurately predicting frozen soils.

Antarctica is the coldest continent on the earth. The temperature of the highest point in Antarctica, Dome A, has reached -90.0 ℃. Three extreme low temperature events are simulated through Polar Weather Research and Forecast Model (WRF) 3.8.1. Compared with the observation of automatic weather station at Dome A, the simulated results are satisfactory. Diagnoses are made based on the simulation outputs. The following results were obtained: the enhancement of the high-pressure center between the Indian Ocean and the Atlantic Ocean and its high-pressure ridge stretching into Antarctic plateau led the pressure rising at Dome A and made this region fine and cloudless, which were the foundation for the extreme low temperature events;

the enhancement of the Antarctic cold vortex, longstanding cold advection and stable thermal inversion layer provided enough cooling factors and strengthen the radiation cooling effect at night; stable vertical field and extremely low downward longwave radiation made the extreme cold events continue. However, more in-situ observations are required, especially in the vast interior of Antarctica.

The glacial outburst flood of Lake Merzbacher is the serious disaster source of the Aksu River. In this study, utilizing the remote sensing data of Landsat, HJ-1A/B and GF-1 from 1998 through 2017, the lake’s area was abstracted with the method of Munsell HSV Transform. By analyzing and comparing the maximum lake area of different years, it was found that the area of Lake Merzbacher has shrank from 3. 75 km2 to 2.87 km2 in recent 20 years. Lake Merzbacher contains two small lakes, Upper lake and Lower lake. Lower lake which dominates the storage of the whole lake has shrank from 3.3 km² to 1.88 km² during 1998—2017. On the contrary, Upper lake has expanded. As a consequence, the total water capacity has reduced. The relationship between the area of Lake Merzbacher and temperature was examined, and it is found that positive accumulated temperature affected by the lake’s outburst date has strong positive correlation with the area of Lower lake, which means that temperature can make a difference to the lake’s area through impacting meltwater to the lake and the stability of the dam.

Base-flow is main supply source of runoff during the dry season. The reliable method of base-flow separation plays an important role in base-flow research and the management and utilization of water resources. Based on the daily runoff data from Changmabao Hydrological Station in the upper reaches of the Shule River from 2007 through 2016, in this study, using single parameter digital filtering method, minimum smoothing method, recursive digital filter technique, fixed interval method, sliding interval method and local minimum method, the base-flow is separated. The results show that the four methods can accomplish the automatic separation of base-flow. The above separated base-flow hydrograph is smooth. There are four base-flow separation methods, which have different base-flow index, ranging from 0.49 to 0.72. The results of recursive digital filtering method have the highest stability. When the filtering parameter β takes a value of 0.95, it is an optimal parameter of the single parameter digital filtering method. The minimum smoothing method, sliding interval method, local minimum method and single parameter digital filtering method (β=0.95) have high Nash-Sutcliffe efficiency coefficients with the average relative error less than 10%. The base-flow simulated results show that these methods were stable, reliable, accurately and could be used as the optimal separation methods to estimate base-flow in the study area.

Abstract: The water vapor in atmosphere is the material basis for formation of clouds and precipitation. It is closely related to the global water cycle and energy balance, and has an important impact on climate and weather. In this study, based on monthly reanalysis grid points (2.5°×2.5°) data within 1979—2016 from the NCEP/NCAR, the specific humidity, water vapor flux at 1 000 hPa of Northeast China are taken as the research object, quantitative at 1 000 hPa, 850 hPa, 700 hPa and 500 hPa. Based on the reanalysis of monthly NCEP/NCAR data, in this study, the climatic characteristics and long-term trend change of specific humidity at different altitudes over Northeast China have been comprehensively analyzed, as well as the seasonal changes of integrated water vapor flux. The results show that the vertical distribution characteristics of water vapor in Northeast China are that the water vapor content began to drop from 500 hPa level, the higher the elevation the lower the water vapor content. The specific humidity in Northeast China had showed an overall downward trend from 1979 to 2000. After 2000, an ascending trend has been seen. Spatially, in Northeast China there is a latitude effect significantly, the water vapor content is mainly concentrated in the south. In a year round the water vapor content in Northeast China is the maximum in July and the minimum is between December and January of next year. The sources of summer water vapor are mainly from the South China Sea, followed by the Bohai Sea and the Yellow Sea. In other seasons, westerly wind is the main source of water vapor.

In order to obtain the effect of freezing-thawing cycles on the pore size distribution of loess, remolded loess was taken as the research object, the pore characteristics of loess samples after different freeze-thaw cycles were tested by mercury intrusion porosimetory. In addition, quantitative characterization and comparative study of microscopic pore structure of loess were carried out by using three kinds of fractal models. The results showed that the pore distribution curve of loess without freezing-thawing action is unimodal, while the pore distribution curve of loess subjected to freezing-thawing was bimodal or even multimodal. The freezing-thawing cycle has a considerable influence on the pore size within the range of 0.1~10?m in loess. The porosity of loess increased during the first ten freezing-thawing cycles, especially after six freezing-thawing cycles, the porosity increased by about 18.8%. As freezing-thawing continued, the porosity of loess decreased and stabilized. The pore size distribution of loess after different freezing-thawing cycles exhibits a good statistical fractal characteristics. Based on the thermodynamic model and capillary pressure curve method to characterize the pore structure of loess, the loess pores exhibit significant fractal characteristics and can give a unique and reasonable fractal dimension over the entire pore size scale. However, while the menger sponge model is adopted, the fractal characteristics of loess pores exhibit multi-scale fractal, and there are different fractal dimensions in different scales. Combined with fractal theory, it can be concluded that freezing-thawing changes the porosity uniformity and complexity of loess.