Snow loads on wire mesh and cable net rockfall slope protection systems

Snow load on mesh systems is complicated by many factors. This paper presents field instrumentation data on snow load variation with temperature, snowfall and snow depth on a mesh system. It was found that snow load pattern on mesh systems changed with temperature even without variation in snow depth. It reached its maximum value when the temperature rose just above freezing to melt the interface. The field data was used to formulate appropriate snow load models for the various conditions of temperature in the field. The snow load models were used to study the performance of a number of mesh systems in North America and estimate the interface friction that was prevalent for the different surface conditions.     

Analysis of snowpack dynamics during the spring melt season for a sub‐alpine site using point measurements and numerical modeling

Snowpack dynamics through October 2014–June 2017 were described for a forested, sub‐alpine field site in southeastern Wyoming. Point measurements of wetness and density were combined with numerical modeling and continuous time series of snow depth, snow temperature, and snowpack outflow to identify 5 major classes of distinct snowpack conditions. Class (i) is characterized by no snowpack outflow and variable average snowpack temperature and density. Class (ii) is characterized by short durations of liquid water in the upper snowpack, snowpack outflow values of 0.0008–0.005 cm hr^?1, an increase in snowpack temperature, and average snow density between 0.25–0.35 g cm^?3. Class (iii) is characterized by a partially saturated wetness profile, snowpack outflow values of 0.005–0.25 cm hr^?1, snowpack temperature near 0 °C, and average snow density between 0.25–0.40 g cm^?3. Class (iv) is characterized by strong diurnal snowpack outflow pattern with values as high as 0.75 cm hr^?1, stable snowpack temperature near 0 °C, and stable average snow density between 0.35–0.45 g cm^?3. Class (v) occurs intermittently between Classes (ii)–(iv) and displays low snowpack outflow values between 0.0008–0.04 cm hr^?1, a slight decrease in temperature relative to the preceding class, and similar densities to the preceding class. Numerical modeling of snowpack properties with SNOWPACK using both the Storage Threshold scheme and Richards' equation was used to quantify the effect of snowpack capillarity on predictions of snowpack outflow and other snowpack properties. Results indicate that both simulations are able to predict snow depth, snow temperature, and snow density reasonably well with little difference between the 2 water transport schemes. Richards' equation more accurately simulates the timing of snowpack outflow over the Storage Threshold scheme, especially early in the melt season and at diurnal timescales.     

黄河源区多、少雪年土壤冻融特征分析

利用2011年10月至2017年12月黄河源区鄂陵湖野外观测数据,对比分析多雪年与少雪年土壤冻结与消融时间、土壤温湿度、地表能量分量的变化特征。结果表明:多雪年地表反照率偏高,净辐射偏低,地表感热输送偏低,土壤由热“源”转为热“汇”的时间晚于少雪年。积雪可减少土壤吸收辐射能量,减少地表感热通量,在土壤完全冻结期与消融期增大地表潜热通量,在完全冻结期,减少土壤向大气的热输送,在消融期,减少大气向土壤的热输送。积雪在冻结期有降温作用,使得多雪年土壤较早发生冻结,且同一时期土壤温度偏低;在完全冻结期有保温作用,使得土壤温度偏高;在消融期有保温(“凉”)作用,使得消融较晚,且同一时期土壤温度偏低。在整个积雪年内,多雪年浅层土壤湿度高于少雪年,积雪对浅层土壤有保湿作用。积雪使土壤开始冻结时间有所提前,开始消融的时间有所滞后,可延长该年土壤完全冻结持续天数。     

Body motion in liquid under ice plate with snow cover

The motion of a submarine in liquid under an ice plate covered with flooded snow is considered. The ice is modelled as an elastic plate and the snow cover is modelled as a viscous layer on the top of the plate. The submarine is modelled as a slender solid of revolution with scale 1:300. The experimental and theoretical study of the influence of the viscous snow layer on deflections of the floating ice plate is conducted. The viscous layer reduces the amplitudes of flexural-gravity waves. The greatest influence of the viscous layer on the plate deflections is achieved for velocities of the submarine, where the waves of maximum amplitude are generated. Theoretical results are in good qualitative and quantitative agreement with the model experiments.     

河西走廊地质历史中宋辽干冷期灾变事件及其影响

宋辽寒冷干旱期的急剧降温,使河西地区降水量迅速减少,气候变得更为干旱。植被枯萎,风暴、沙暴、尘暴、火灾、旱灾、饥荒等灾害事件频繁发生,从而引发了一系列生态环境问题和战争动乱,对中国政治、社会、经济、文化产生重大影响。依据历史资料和考古研究成果及地质记录中“事件标志层”层位、年代,确定宋辽寒冷干旱期发生于公元1000~1050年,发展于公元1050~1100年,强盛于公元1100~1320年,消亡于公元1320~1335年。     

A Case study of a snowstorm at the Great Wall Station,Antarctica

A case of a snowstorm at the Great Wall Station was studied using data of NCEP (National Centers for Environmental Prediction) analysis, in situ observations and surface weather charts. The storm occurred on August 29th,2006, and brought high winds and poor horizontal visibility to the region.It was found that the storm occurred under the synoptic situation of a high in the south and a low in the north. A low-level easterly jet from the Antarctic continent significantly decreased the air temperature and humidity.Warm air advection at high level brought sufficient vapor from lower latitudes for the snowstorm to develop.The dynamic factors relating to strong snowfall and even the developmentof a snowstorm were deep cyclonic vorticity at middle and low levels,the configuration of divergence at high level and convergence at low level, and strong verticaluplift. There was an inversion layer in the low-level atmosphere during the later phase of the storm.This vertical structure of cold air at low levels and warm air at high levels may have been important to the longevity of the snowstorm.     

上海及其邻区潜在地质灾害的构造背景与成因机理

本文基于上海及其邻区活动断裂构造及有关地区潜在地质灾害特点的研究,论证了上海及其邻区潜在地质灾害的三种基本类型及其构造背景与成因机理;指出:上海及其邻区楔形断裂系统的存在与活动是诱发有关地区潜在地质灾害的主导因素。文中明确指出了上海及其邻区楔形断裂系统的研究在相关地区进行潜在地质灾害评价与预测方面的应用前景与发展方向。     

Fuzzy factorial analysis of snow avalanches

The mutual influence of 21 factors pertaining to terrain, weather, forest and snowpack have been discussed by 10 experts. The semantic (nil, weak, medium, high) evaluations are translated as membership degrees of fuzzy sets, and averaged between the experts by taking their fuzzy expectation value, yielding a 21 × 21 fuzzy matrix for direct interactions. Fuzzy successive multiplications and additions of the matrix give the indirect interactions. The activity and the passivity of the factors with respect to avalanches is represented by directed weighted graphs, and the average semantic values by a 4 × 4 matrix: the activity (passivity) is weak (strong) for tree damage; medium (nil) for altitude; medium (weak) for ground shape; medium (medium) for vegetation, soil, wind, microclimate, tree type, vertical distribution and mechanics of trees, snowpack distribution and snow gliding; strong (nil) for ground inclination and exposition, weather; strong (medium) for heat, precipitation, horizontal distribution of trees, snowpack constitution and stability.     

Characteristics and mitigation of the snow avalanche hazard in Kaghan Valley,Pakistan Himalaya

Snow avalanche hazards in mountainous areas of developing countries have received scant attention in the scientific literature. The purpose of this paper is to describe this hazard and mitigative measures in Kaghan Valley, Pakistan Himalaya, and to review alternatives for future reduction of this hazard. Snow avalanches have long posed a hazard and risk to indigenous populations of the Himalaya and Trans-Himalaya mountains. Land use intensification due to population growth, new transportation routes, military activity and tourism is raising levels of risk. The history of land use in the study area is such that investigations of avalanche hazard must rely on different theoretical bases and data than in most industrialised countries. Despite the intensive use of valley-bottom land which is affected by avalanches, a number of simple measures are currently employed by the indigenous population to mitigate the hazard. Out-migration during the winter months is the most important one. During the intensive use period of summer avalanche-transported snow provides numerous resources for the population. In Kaghan the avalanche hazard is increasing primarily as a result of poorly located new buildings and other construction projects. The large scale of avalanche activity there rules out any significant improvement or protection of the currently difficult winter access. Instead, future mitigation of the hazard should focus on protecting the small number of winter inhabitants and minimising property damage.     

云南省40年降水的基本特征

根据云南省１９５１－１９９０年１８个站的降水资料，用正交函数展开，由方差贡献最大的前三个特征向量场分析了云南省降水距平均的典型分布，指出云南省全省范围内的降水距平同号较少发生，而是较多的发一降水距平异号。进而分析了四十年降水的年际变化特征，并分析了青藏高原积雪对云南降水的影响。