Numerical Simulation of Sensitivities of Snow Melting to Spectral Composition of the Incoming Solar Radiation

Snow albedo is an important factor influencing the snow surface energy budget and snow melting, yet uncertainties remain in the calculation of spectrally resolved snow surface albedo because the spectral composition （visible versus near infrared） of the incident solar radiation is seldom available. The influence of the spectral composition of the incoming solar radiation on the snow surface albedo, snow surface energy budget, and final snow ablation is investigated through sensitivity experiments of four snow seasons at two open sites in the Alps by using a multi-layer Snow-Atmosphere-Soil-Transfer scheme （SAST）. Since the snow albedo in the near infrared （NIR） spectral band is significantly lower than that in the visible （VIS） band, and almost the entire NIR part of the solar radiation is absorbed in the top layer of the snow pack, given a fixed amount of incoming solar radiation, a lower VIS/NIR ratio implies that more NIR radiation is reaching the ground surface and more is absorbed by the top layer of the snow pack, therefore, speeding up the snow melting and increasing the surface runoff, although a lesser part of the solar radiation in the visible band is transmitted into and trapped by the sub-layer of the snow pack. The above VIS/NIR ratio effect of the incoming solar radiation can result in a couple of days difference in the timing of snow ablation and it becomes more significant in late spring when the total solar radiation is intensified with seasonal evolution. Snow aging also slightly intensifies this VIS/NIR ratio effect.

The Electrical Properties and Snow Melting of Graphite Slurry Infiltrated Steel Fiber Concrete

The conductivity property of graphite slurry infiltrated steel fiber concrete （GSIFCON） was investigated by the four-probe method. The experimental results show that the electrical resistivity of GSIFCON decreases significantly at a specific concentration of graphite, i e, the percolation concentration. A model was accordingly developed to explain its conductive mechanism, where graphite particles could be served as bridge for conductive network between unconnected fiber chains. For an application, snow melting test of GSIFCON was carried out and a simple heating power analysis was performed. The results reveal that the thermal energy produced by GSIFCON makes snow melting effectively and the electrothermal efficiency can reach approximately 20%.

Assessment of the Mechanical Properties of Carbon-Fiber Heating Cables in Snow and Ice Melting Applications

The use of carbon-fiber heating cables(CFHC)to achieve effective melting of snow and ice deposited on roads is a method used worldwide.In this study,tensile and compressive tests have been conducted to analyze the mechan-ical properties of the CFHC and assess whether the maximum tensile and compressive strengths can meet the pavement design specifications.In order to study the aging produced by multiple cycles of heating and cooling,in particular,the CFHC was repeatedly heated in a cold chamber with an ambient temperature ranging between-20℃ and+40℃.Moreover,to evaluate how the strength of the pavement is affected by its presence,the CFHC was embedded at different depths and concrete blocks with different curing ages were subjected to relevant com-pression and splitting tensile tests.Numerical simulations based on the ANSYS software have also been performed and compared with the outcomes of the static loading tests.The results show that the CFHC embedded in the concrete does not affect the compressive splitting tensile strengths of the pavement.Overall,the CFHC meets the conditions required for continued use in road ice melting applications.

Hydrological processes of glacier and snow melting and runoff in the Urumqi River source region, eastern Tianshan Mountains, China

Hydrological processes were compared, with and without the influence of precipita- tion on discharge, to identify the differences between glacierized and non-glacierized catchments in the Urumqi River source region, on the northern slope of the eastern Tianshan Mountains, during the melting season （May-September） in 2011. The study was based on hydrological data observed at 10-min intervals, meteorological data observed at 15-min intervals, and glacier melting and snow observations from the Empty Cirque, Zongkong, and Urumqi Glacier No.1 gauging stations. The results indicated that the discharge differed markedly among the three gauging stations. The daily discharge was more than the nightly discharge at the Glacier No.1 gauging station, which contrasted with the patterns observed at the Zongkong and Empty Cirque gauging stations. There was a clear daily variation in the discharge at the three gauging stations, with differences in the magnitude and duration of the peak discharge. When precipitation was not considered, the time-lags between the maximum discharge and the highest temperature were 1-3 h, 10-16 h, and 5-11 h at the Glacier No.l, Empty Cirque, and Zongkong gauging stations, respectively. When precipitation was taken into consideration, the corresponding time-lags were 0-1 h, 13 h, and 6-7 h, respectively. Therefore, the duration from the generation of discharge to confluence was the shortest in the glacierized catchment and the longest in the catchment where was mainly covered by snow. It was also shown that the hydrological process from the generation of discharge to confluence shortened when precipitation was considered. The factors influencing changes in the discharge among the three gauging stations were different. For Glacier No.1 station, the discharge was mainly controlled by heat conditions in the glacierized region, and the discharge displayed an accelerated growth when the temperature exceeded 5℃ in the melt season. It was found that the englacial and subglacial drainage channel of Glacier No.1 had become simpler during the past 20 years. Its weaker retardance and storage of glacier melting water resulted in rapid discharge confluence. It was also shown that the discharge curve and the time-lag between the maximum discharge and the highest temperature could be used to reveal the evolution of the drainage system and the process of glacier and snow melting at different levels of glacier coverage.

Black Carbon Size in Snow of Chinese Altai Mountain in Central Asia

Black carbon(BC)in snow plays an important role to accelerate snow melting.However,current studies mostly focused on BC concentrations,few on their size distributions in snow which affected BC’s effect on albedo changes.Here we presented refractory BC(rBC)concentrations and size distributions in snow collected from Chinese Altai Mountains in Central Asia from November 2016 to April 2017.The results revealed that the average rBC concentrations were 5.77 and2.82 ng g-1for the surface snow and sub-surface snow,which were relatively higher in the melting season(April)than that in winter(November-January).The mass median volume-equivalent diameter of rBC size in surface snow was approximately at 120-150 nm,which was typically smaller than that in the atmosphere(about 200 nm for urban atmosphere).However,there existed no specific mass median volume-equivalent diameter of BC size for sub-surface snow in winter.While during the melting season,the median mass size of rBC in sub-surface snow was similar to that in surface snow.Backward trajectories indicated that anthropogenic sourced BC dominated rBC in snow(70%-85%).This study will promote our understanding on BC size distributions in snow,and highlight the possible impact of BC size on climate effect.

Seasonal Behavior of Pavement in Geothermal Snow-Melting System with Solar Energy Storage

A two-dimensional unsteady heat transfer model of pavement of geothermal road snow-melting system (GRSS) with solar energy storage is established and numerical simulation is carried out based on annual hourly meteorological data and boundary conditions. Simulated results show that ground surface temperature and heating flux decrease with the increase of buried depth, but increase with the increase of fluid temperature in winter. Heat-extracted amount and efficiency drop with the increase of fluid temperature in summer.Compared with ambient temperature, solar radiation has more direct influence on the heat-extracted flux of pipe walls of GRSS in summer. The relationships among maximum and idling snow-melting load, the rate of snowfall, ambient temperature and wind speed are made clear, which provides necessary references for the design and optimization of a practical road snow-melting system.

The Variability of the Snow and Ice Melt in Alpine Rivers in Northwestern China

The study of snow and ice melt(SIM) is important in water-scarce arid regions for the assessment of water supply and quality. These studies involve unique difficulties, especially in the calibration of hydro-models because there is no direct way to continuously measure the SIM at hydrostations. The recursive digital filter(RDF) and the isotopic hydro-geochemical method(IHM) were coupled to separate the SIM from eight observed series of alpine streamflows in northwestern China.Validation of the calibrated methods suggested a good capture of the SIM characteristics with fair accuracy in both space and time. Applications of the coupled methods in the upper reaches of the Hei River Basin(HRB) suggested a double peak curve of the SIM fraction to streamflow for the multi-component recharged(MCR) rivers, while a single peak curve was suggested for the rainfall-dominant recharged(RDR)rivers. Given inter-annual statistics of the separation,both types of the alpine rivers have experienced an obvious decrease of SIM since 1960 s. In the past 10 years, the SIM in the two types of rivers has risen to the levels of the 1970 s, but has remained lower than the level of the 1960 s. The study provided a considerable evidence to quantify the alpine SIM based on the separation of observed data series at gauge stations. Application of the coupled method could be helpful in the calibration and validation of SIM-related hydro-models in alpine regions.

Large spread across AeroCom Phase II models in simulating black carbon in melting snow over Arctic sea ice

Over two dozen global atmospheric chemistry models contributing to the Aerosol Comparisons between Observations and Models(AeroCom)project were used in this study to drive the Los Alamos sea ice model to simulate the black carbon(BC)concentration in melting snow on Arctic sea ice.Measurements of BC during the melting season show concentrations in the range 2.8–41.6 ng·g−1(average:15.3 ng·g−1)in the central Arctic Ocean and Canada Basin.Most results from models contributing to the Phase I project were within the 25th and 75th percentiles of the observations,and the multimodel mean was slightly lower than that of the observations.In contrast,there was larger divergence among the Phase II model simulations and the mean value of BC was overestimated.The multimodel mean bias was−3.1(−11.2 to+6.7)ng·g−1 for Phase I models and+3.9(−9.5 to+21.3)ng·g−1 for Phase II models.The differences between the models of the two phases were probably attributable to the updated aerosol scheme in the new contributions,in which removal processes are parameterized by considering the actual dimensions and chemical compositions of the particles.This means the removal mechanism acts in a way that is more selective and leads to more BC particles being transported to the Arctic.In addition,higher spatial resolution could be another important reason for overestimation of BC concentration in snow in Phase II models.

Densification and grain coarsening of melting snow

A field work was conducted at Moshiri in Japan. The work included intensive snow pit work, taking snow grain photos, recording snow and air temperatures, as well as measuring snow water content. By treating the snow as a viscous fluid, it is found that the snow compactive viscosity decreases as the density increases, which is opposite to the relation for dry snow. Based on the measurements of snow grain size, it is shown that, similar to the watersaturated snow, the frequency distributions of grain size at different times almost have the same shape. This reveals that the waterunsaturated melting snow holds the same graincoarsening behavior as the watersaturated snow does. It is also shown that the waterunsaturated melting snow coarsens much more slowly than the watersaturated snow. The C value, which is the viscosity when the snow density is zero, is related to the mean grain size and found to decrease with increasing grain size. The decreasing rate of C value increases with decreasing graincoarsening rate.

流体加热融雪系统运行对道路结构温度分布特性影响分析

为了明确流体加热道路融雪系统运行对道路结构短期/长期温度分布特性的影响,利用室外足尺试验系统对比分析了普通水泥混凝土路面结构与流体加热道路融雪系统道路结构在温度、温变速率及温度梯度分布特性等方面的差异,阐明了系统运行对道路结构短期/长期温度分布特性的影响规律。结果表明:融雪系统运行初期,快速上升的流体温度对管壁-路面材料界面存在强烈的温度冲击作用;随着系统持续运行,管壁-路面材料界面的温变速率逐渐减小并趋于稳定,且小于普通路面最大温变速率;同时,融雪系统的运行增大了路面结构内部的温度梯度,改变了路面结构一定深度范围内的热量传递方向。融雪系统道路结构年周期温度分布的观测结果表明:融雪系统的运行可在较短的时间内释放大量热能,降低了道路结构内部热量的散失,有效延缓了季节性冰冻地区冬季道路结构温度的降低及冻结深度的发展。

基于改进SHRP融冰试验的氯盐融雪剂性能研究

氯盐融雪剂因其融冰除雪性能优异、价格低廉、易于获取而得到广泛应用。为探究氯盐融雪剂的温度适用性不同、标准不统一、撒布方式粗略等问题,该文通过改进的SHRP融冰试验,分析了温度、固液态及撒布方式对NaCl、CaCl_(2)、MgCl_(2) 3种常用氯盐融雪剂除冰性能的影响。试验结果表明:氯盐融雪剂的除冰性能对温度具有显著的敏感性;MgCl_(2)、CaCl_(2)两种融雪剂在融化过程中存在“放热”效应;同种氯盐融雪剂在固态下的融冰效率高于液态下的;同种氯盐融雪剂在不同撒布方式下融冰效率不同,其中,在线性撒布下除冰能力最强。根据试验结果,建议使用固态线性撒布的方式,并根据环境温度选择适宜的融雪剂。

面向未来低碳道路养护的超薄罩面功能性研究综述

Highway maintenance mileage reached 5.25 million kilometers in China by 2021.Ultra-thin overlay is one of the most commonly used maintenance technologies,which can significantly enhance the economic and environmental benefits of pavements.To promote the low-carbon development of ultrathin overlays,this paper mainly studied the mechanism and influencing factors of several ultra-thin overlay functions.Firstly,the skid resistance,noise reduction,rutting resistance,and crack resistance of ultrathin overlays were evaluated.The results indicated that the high-quality aggregates improved the skid and rutting resistance of ultra-thin overlay by 5%-20%.The optimized gradations and modified binders reduced noise of ultra-thin overlay by 0.4-6.0 dB.The high viscosity modified binders improved the rutting resistance of ultra-thin overlay by about 10%-130%.Basalt fiber improved the cracking resistance of ultra-thin overlay by more than 20%.Due to the thinner thickness and better road performance,the performance-based engineering cost of ultra-thin overlay was reduced by about 30%-40%compared with conventional overlays.Secondly,several environmentally friendly functions of ultra-thin overlay were investigated,including snow melting and deicing,exhaust gas purification and pavement cooling.The lower thickness of ultra-thin overlay was conducive to the diffusion of chloride-based materials to the pavement surface.Therefore,the snow melting effect of self-ice-melting was better.In addition,the ultra-thin overlay mixture containing photocatalytic materials could decompose 20%-50%of the exhaust gas.The colored ultra-thin overlay was able to reduce the temperature of the pavement by up to 8.1℃.The temperature difference between the upper and lower surfaces of the ultra-thin overlay containing thermal resistance materials could reach up to 12.8℃.In addition,numerous typical global engineering applications of functional ultra-thin overlay were summarized.This review can help better understand the functionality of ultra-thin overlays and promote the realization of future multi-functional and low-carbon road maintenance.

相变沥青混合料融雪效果及评价指标研究

为确定DTC相变材料(phase change material,PCM)在沥青路面中的融雪效果及评价指标,通过设计室内和室外融雪试验,以未掺加相变材料的沥青混合料试件作为对照组,研究并分析低温下相变沥青混合料的融雪效果。结果表明:相变材料在沥青混合料中具有明显的调温作用,掺量越大,融雪效果越明显;相变材料掺量为0.5%、积雪厚度分别为1.5 cm和3.0 cm时,与普通沥青混合料相比,相变沥青混合料融雪速率分别提高19.0%和16.0%。基于室内和室外融雪试验,提出以积雪厚度变化率(Δh)和余雪覆盖率(residual snow coverage,RSC)作为相变沥青混合料融雪效果的综合评价指标。

Preparation and Analysis of Carbon Fiber-Silicon Carbide Thermally Conductive Asphalt Concrete

An experimental investigation into the thermal conductivity of CF-SiC two-phase composite asphalt concrete is presented.The main objective of this study was to verify the possibility of using SiC powder instead of mineral powder as the thermal conductive filler to prepare a new type of asphalt concrete and improve the efficiency of electrothermal snow and ice melting systems accordingly.The thermal conductivity of asphalt concrete prepared with different thermally conductive fillers was tested by a transient plane source method,and the related performances were measured.Then the temperature rise rate and surface temperature were studied through field heating tests.Finally,the actual ice melting efficiency of the thermally conductive asphalt concrete was evaluated using an effective electrothermal system.As shown by the experimental results,the composite made of SiC powder and carbon fiber has a high thermal conductivity.When SiC replaces mineral powder,the thermal conductivity of the asphalt mixture increases first and then decreases with the increase of carbon fiber content.In the present study,in particular,the thermal conductivity attained a peak when the carbon fiber content was 0.2%of the aggregate mass.

基于雪消融算法优化长短时网络的齿轮箱油温预警方法

风电机组数据的复杂多变导致所采集数据的数据特征之间深度冗余。数据特征深度冗余导致常规预测模型容易陷入局部最优,进而使模型预测精度较低。为提高齿轮箱油温预测精度,首先,采用随机森林进行特征提取,利用改进的自适应噪声集合经验模态分解对选定的特征数据进行分解,使用主成分分析法对数据进行降维处理;然后,运用雪消融优化算法来搜索长短期记忆递归神经网络模型最佳超参数设置。实验结果证明,该方法可以有效提高齿轮箱油温异常预警模型的精度。

干湿循环作用下融雪剂对玻璃纤维水泥土力学性能影响的试验研究

为研究在干湿循环作用下不同种类融雪剂对玻璃纤维水泥土力学性能的影响,制备浓度为0.2mol/L的醋酸钾、氯化镁和硫酸钠溶液作为融雪剂溶液,将养护后的无纤维水泥土和有纤维水泥土试块在不同种类的融雪剂溶液中浸泡3d,然后将试块取出放入烘干箱内分别进行8~10次干湿循环。进而分析融雪剂类型、干湿循环次数对试块表面破坏状态、强度和质量等的影响。试验结果表明:经过10次干湿循环后,醋酸钾融雪剂溶液对试块质量和强度的影响程度小于氯化镁溶液和硫酸钠溶液,说明醋酸钾融雪剂对水泥土侵蚀作用较小;试块表面裂纹随着干湿循环次数的增加逐渐增多加深,在经历相同干湿循环次数后,有纤维水泥土试块的裂纹发展程度、质量损失率和强度损失率均低于无纤维水泥土试块,说明通过添加玻璃纤维可有效提高水泥土抗干湿循环和融雪剂侵蚀的能力。

甘肃积石山地震液化型泥流特征、成因及其对黄河上游盆地地震次生灾害风险评估的启示

北京时间2023年12月18日23点59分30秒,甘肃省临夏州积石山县发生Ms 6.2级浅源地震,地震在青海省民和县中川乡诱发了一处同震特大型规模泥流灾害,造成了特大型灾难事件的发生。笔者采用现场调查、无人机摄影测量、现场取样及室内测试等研究方法对此次泥流灾害发育特征及成因进行分析。结果表明:①该泥流具有典型沟谷型泥石流平面特征,形成区、流通区和堆积区分界明显,泥流主要物源为山前洪积粉质黏土。②地震、降雪消融、农田冬灌、低温冻结,为泥流提供了初始动力并抬升了局部地下水位,是该泥流灾害的主要诱因;地形坡度、地层岩性,为泥流提供了后续运动势能和振动液化条件,是该泥流灾害的内因。③泥流运移过程中存在侧向和底部铲刮效应,尤其在3处流向改变区侧向铲刮、局部堆积显著,最终快速流入沟口金田村和草滩村。分析结果可为官亭盆地乃至黄河上游沉积盆地地震次生灾害风险评价工作提供思路与理论依据。

Observation and modelling of snow and sea ice mass balance and its sensitivity to atmospheric forcing during spring and summer 2007 in the Central Arctic

Snow depth and sea ice thickness were observed applying an ice mass balance buoy(IMB)in the drifting ice station Tara during the International Polar Year in 2007.Detailed in situ observations on meteorological variables and surface fluxes were taken during May to August.For this study,the operational analyses and short-term forecasts from two numerical weather prediction(NWP)models(ECMWF and HIRLAM)were extracted for the Tara drift trajectory.We compared the IMB,meteorological and surface flux observations against the NWP products,also applying a one-dimensional thermodynamic sea ice model(HIGHTSI)to calculate the snow and ice mass balance and its sensitivity to atmospheric forcing.The modelled snow depth time series,controlled by NWP-based precipitation,was in line with the observed one.HIGHTSI reproduced well the snowmelt onset,the progress of the melt,and the first date of snow-free conditions.HIGHTSI performed well also in the late August freezing season.Challenges remain to model the“false bottom”observed during the melting season.The evolution of the vertical temperature profiles in snow and ice was better simulated when the model was forced by in situ observations instead of NWP results.During the melting period,the nonlinear ice temperature profile was successfully modelled with both forcing options.During spring and the melting season,total sea ice mass balance was most sensitive to uncertainties in NWP results for the downward longwave radiation,followed by the downward shortwave radiation,air temperature,and wind speed.

相变材料在冬季沥青路面中的应用分析

沥青路面在冬季低温雨雪气候下易发生结霜、结冰现象,致使路面抗滑性能降低,从而导致事故发生率上升,给行车安全及路面使用性能带来严重影响。传统的被动式除雪法效率低,且须占用行车道影响道路正常运行,化学融雪剂还会造成土壤和水污染。本文通过文献调研,总结常见的主动融雪化冰路面类型,分析相变材料在沥青路面中的应用研究重点,提出将相变材料掺入沥青路面中,以预防或减少冬季沥青路面冰冻病害。

Significant Variations of Surface Albedo during a Snowy Period at Xianghe Observatory,China

Surface albedo over typical types of surfaces in the North China Plain was observed using a Multi-field Albedo Observation System before and after several snowfalls from 13 to 27 February 2005. Dramatic variations of the surface albedos of bare land, a frozen pond, and withered grassland during that period were analyzed. Under cloudy sky, the mean surface albedo of bare land was about 0.23, but it immediately rose to 0.85 when the surface was covered by fresh snow. The albedo decreased gradually to normal levels afterwards. The melting processes were different depending on the characteristics of the underlying surfaces. For example, over grassland the surface albedo was relatively lower after snowfall, and as a result, more solar energy could be absorbed and consequently the snow melting process was accelerated. Significant variations of surface albedo cannot be easily captured by satellite observations; therefore, detailed measurements of surface albedo and related parameters are essential for determining the impact of snow on the energy budget of the Earth.