Rock-ice avalanches in cold high-mountain regions pose severe hazards due to their high mobility,yet the quantitative controls of particle-size ratio and ice content remain insufficiently constrained.This study invest...Rock-ice avalanches in cold high-mountain regions pose severe hazards due to their high mobility,yet the quantitative controls of particle-size ratio and ice content remain insufficiently constrained.This study investigates their coupled effects using inclinedflume experiments and Discrete Element Method(DEM)simulations,covering three gravel sizes(2-5 mm,5-7 mm,7-10 mm)and four ice-content levels(0%,20%,40%,60%).Run-out distance,velocity,energy components,flow regime(Savage number),and segregation indexαwere quantified.Increasing ice content significantly enhances mobility,but with diminishing marginal effectiveness.From 0%to 40%ice content,run-out distance increases by 41%-86%,whereas the additional increase from 40%to 60%contributes only 12%-23%.Particle-size ratio strongly governs segregation intensity.Fine-gravel groups reach segregation indices ofα=0.92-0.98,indicating nearly complete upward migration of ice,whereas medium-gravel and coarse-gravel groups exhibit much weaker segregation,stabilizing atα=0.68-0.74 and 0.60-0.69.Savage number analyses reveal marked flow-regime transitions.At 0%ice content,Savage numbers reach 1.0-1.5,indicating a collisional regime.Increasing ice content suppresses collisionality,with Savage numbers decreasing to 0.03-0.07 at 60%ice content,consistent with dense-regime flow.DEM energy analyses confirm this regime shift:for finegravel mixtures,collision energy decreases by 14%,while sliding-friction energy increases by 33%as ice content increases from 0%to 60%,reflecting enhanced overburden effects imposed by upward-segregated ice layers.Medium and coarse mixtures exhibit weaker or opposite energy-shift patterns,demonstrating strong size dependence.Mechanistically,large particle-size contrasts promote strong segregation and form dense basal rock layers that increase basal friction and reduce mobility.When particle sizes are similar or ice content is high,segregation remains limited,allowing ice to mix into the basal layer,thereby reducing basal friction and enhancing mobility.This research quantitatively demonstrates how composition controls particle spatial distribution,flow regime,and energy dissipation,offering new mechanistic insights into the propagation and deposition behaviors of rock-ice avalanches and improving hazard assessment in vulnerable high-mountain regions.展开更多
Abstract To investigate the use of the three-point bending method and supplement the corresponding strength data of compacted snow for transportation-related applications in cold regions,compacted snow beams with an a...Abstract To investigate the use of the three-point bending method and supplement the corresponding strength data of compacted snow for transportation-related applications in cold regions,compacted snow beams with an average density of 592 kg·m−3 were fabricated and tested at three distinct flexural strain rates.Each strain rate corresponded to the ductile,transitional,and brittle behavior of compacted snow,respectively.The flexural strength,ranging from 0.518 to 0.933 MPa,peaks at the ductile-to-brittle transition,while the flexural modulus,varying between 48.97 and 287.72 MPa,increases with strain rate within the tested range.At the same strain rate corresponding to brittle failure,both mechanical properties of compacted snow exhibit higher values than those of natural snow tested by the authors.Notably,the flexural strain rate at the ductile-to-brittle transition for compacted snow identified in this study is comparable to those previously reported for natural snow under uniaxial tension.Additionally,the obtained strength data are thoroughly compared with existing literature,with detailed discussions provided.The loading rates associated with typical failure modes of compacted snow under bending,together with the obtained strength values,provide methodological guidance and reference data for future in situ testing of compacted snow structures.展开更多
During the winter of 2023/24,three distinct snowfall events occurred in eastern China,significantly impacting agriculture and transportation.The ability to provide subseasonal predictions with lead times beyond the we...During the winter of 2023/24,three distinct snowfall events occurred in eastern China,significantly impacting agriculture and transportation.The ability to provide subseasonal predictions with lead times beyond the weather timescale(longer than one week)is essential for effective disaster prevention and mitigation.Here,we assess the prediction skills of three subseasonal to seasonal(S2S)models from the S2S Prediction project regarding the three snowfall processes during the 2023/24 winter season,and identify the key sources of predictability for such events occurring over eastern China.The surface air temperature(SAT)and precipitation distribution for the three snowfall processes were successfully reproduced up to a lead time of 10–15 and 10 days,respectively.Since the skill in predicting snowfall is reliant on both SAT and precipitation predictions,all three S2S models therefore failed to predict the three snowfall processes beyond the weather timescale.The capacity in capturing Eurasian midlatitude transient Rossby waves and tropical convection anomalies determines the ability of the models to predict snowfall;inaccuracies in modeling these circulation systems result in an underestimation of SAT and precipitation anomalies beyond 15 and 10 days,respectively.Singular value decomposition analysis based on winter seasons from 1991/92 to 2023/24 further identified the coupling modes that exist between Eurasian midlatitude Rossby waves and SAT over eastern China,as well as between tropical convection and precipitation over the same region.These findings suggest that the configurations of tropical and extratropical signals provide universal subseasonal predictability sources for winter snowfall over eastern China.展开更多
本文对2023年12月旅顺出现的连续10天强降雪天气事件进行回顾,运用多个站点观测资料、ERA5的位势高度场、海表温度场、中央气象台的天气形势图与近10年12月连续降雪事件加以对比总结,结果表明:2023年12月平均的冷涡强度最强(中心强度为5...本文对2023年12月旅顺出现的连续10天强降雪天气事件进行回顾,运用多个站点观测资料、ERA5的位势高度场、海表温度场、中央气象台的天气形势图与近10年12月连续降雪事件加以对比总结,结果表明:2023年12月平均的冷涡强度最强(中心强度为5080位势米),强大的冷涡以及极为偏东的高空冷空气堆积是此次连续降雪事件的主要系统;渤海海峡的等温线分布有一个明显的向渤海以北延伸的暖舌(5.2℃~7.6℃之间),平均海气温差在9.4℃,这样冷空气在经过上游暖舌区域增温增湿后可给辽东半岛带来冷流降雪;此次连续降雪既有系统性降雪,又有冷流性降雪,其中冷流降雪(旅顺地区风速小),850 hpa或700 hpa分别处在涡后或槽后脊前,系统性降雪,500 hpa、700 hpa我区均处于高空槽前,850 hpa处于槽后脊前;冷流降雪前及过程中,辽东半岛北部中低空都出现了明显的垂直运动、水汽输送、水汽辐合,700 hpa相较850 hpa更为明显。In this paper, the 10 consecutive days of heavy snowfall in Lvshun in December 2023 was reviewed, and the observation data of several stations, the geopotential height field of ERA5, the sea surface temperature field, and the weather situation chart of the National Meteorological Center of CMA were compared with the continuous snowfall events in December in recent 10 years. The results show that: In December 2023, the average intensity of the cold vortex is the strongest (the central intensity is 5080 geopotential meters), and the strong cold vortex and the accumulation of high altitude cold air very far to the east are the main systems of this continuous snowfall event. The isothermal distribution of the strait has an obvious warm tongue (between 5.2˚C~7.6˚C) extending to the north of the Bohai Sea, the average temperature difference between the sea and the air is 9.4˚C, so that the cold air can bring cold flow snow to the Liaodong Peninsula after warming and humidification in the upstream warm tongue area. The continuous snowfall has both systematic snowfall and cold flow snowfall, among which cold flow snowfall (low wind speed in the Lvshun area), 850 hpa or 700 hpa are behind the vortex or in front of the rear ridge of the trough, and systematic snowfall, 500 hpa and 700 hpa are in front of the upper trough, and 850 hpa is in front of the rear ridge of the trough. Before and during the cold current snowfall, there are obvious vertical movements, water vapor transport and water vapor convergence in the middle and low levels in the northern part of the Liaodong Peninsula, the phenomenon is more pronounced at 700 hpa than 850 hpa.展开更多
基金funded by the Natural Science Foundation of China(Grants No 42277127)。
文摘Rock-ice avalanches in cold high-mountain regions pose severe hazards due to their high mobility,yet the quantitative controls of particle-size ratio and ice content remain insufficiently constrained.This study investigates their coupled effects using inclinedflume experiments and Discrete Element Method(DEM)simulations,covering three gravel sizes(2-5 mm,5-7 mm,7-10 mm)and four ice-content levels(0%,20%,40%,60%).Run-out distance,velocity,energy components,flow regime(Savage number),and segregation indexαwere quantified.Increasing ice content significantly enhances mobility,but with diminishing marginal effectiveness.From 0%to 40%ice content,run-out distance increases by 41%-86%,whereas the additional increase from 40%to 60%contributes only 12%-23%.Particle-size ratio strongly governs segregation intensity.Fine-gravel groups reach segregation indices ofα=0.92-0.98,indicating nearly complete upward migration of ice,whereas medium-gravel and coarse-gravel groups exhibit much weaker segregation,stabilizing atα=0.68-0.74 and 0.60-0.69.Savage number analyses reveal marked flow-regime transitions.At 0%ice content,Savage numbers reach 1.0-1.5,indicating a collisional regime.Increasing ice content suppresses collisionality,with Savage numbers decreasing to 0.03-0.07 at 60%ice content,consistent with dense-regime flow.DEM energy analyses confirm this regime shift:for finegravel mixtures,collision energy decreases by 14%,while sliding-friction energy increases by 33%as ice content increases from 0%to 60%,reflecting enhanced overburden effects imposed by upward-segregated ice layers.Medium and coarse mixtures exhibit weaker or opposite energy-shift patterns,demonstrating strong size dependence.Mechanistically,large particle-size contrasts promote strong segregation and form dense basal rock layers that increase basal friction and reduce mobility.When particle sizes are similar or ice content is high,segregation remains limited,allowing ice to mix into the basal layer,thereby reducing basal friction and enhancing mobility.This research quantitatively demonstrates how composition controls particle spatial distribution,flow regime,and energy dissipation,offering new mechanistic insights into the propagation and deposition behaviors of rock-ice avalanches and improving hazard assessment in vulnerable high-mountain regions.
基金financial support from the Shanghai Science and Technology Committee(Grant no.24DZ3100504)the National Key Research and Development Program of China(Grant no.2022YFC2807102).
文摘Abstract To investigate the use of the three-point bending method and supplement the corresponding strength data of compacted snow for transportation-related applications in cold regions,compacted snow beams with an average density of 592 kg·m−3 were fabricated and tested at three distinct flexural strain rates.Each strain rate corresponded to the ductile,transitional,and brittle behavior of compacted snow,respectively.The flexural strength,ranging from 0.518 to 0.933 MPa,peaks at the ductile-to-brittle transition,while the flexural modulus,varying between 48.97 and 287.72 MPa,increases with strain rate within the tested range.At the same strain rate corresponding to brittle failure,both mechanical properties of compacted snow exhibit higher values than those of natural snow tested by the authors.Notably,the flexural strain rate at the ductile-to-brittle transition for compacted snow identified in this study is comparable to those previously reported for natural snow under uniaxial tension.Additionally,the obtained strength data are thoroughly compared with existing literature,with detailed discussions provided.The loading rates associated with typical failure modes of compacted snow under bending,together with the obtained strength values,provide methodological guidance and reference data for future in situ testing of compacted snow structures.
基金supported by the National Key R&D Program of China(Grant No.2022YFF0801702)the Natural Science Foundation of Jiangsu Province(Grant No.BK20250045&BK20231110)the China Meteorological Administration Innovation and Development Project(Grant No.CXFZ2025Q007).
文摘During the winter of 2023/24,three distinct snowfall events occurred in eastern China,significantly impacting agriculture and transportation.The ability to provide subseasonal predictions with lead times beyond the weather timescale(longer than one week)is essential for effective disaster prevention and mitigation.Here,we assess the prediction skills of three subseasonal to seasonal(S2S)models from the S2S Prediction project regarding the three snowfall processes during the 2023/24 winter season,and identify the key sources of predictability for such events occurring over eastern China.The surface air temperature(SAT)and precipitation distribution for the three snowfall processes were successfully reproduced up to a lead time of 10–15 and 10 days,respectively.Since the skill in predicting snowfall is reliant on both SAT and precipitation predictions,all three S2S models therefore failed to predict the three snowfall processes beyond the weather timescale.The capacity in capturing Eurasian midlatitude transient Rossby waves and tropical convection anomalies determines the ability of the models to predict snowfall;inaccuracies in modeling these circulation systems result in an underestimation of SAT and precipitation anomalies beyond 15 and 10 days,respectively.Singular value decomposition analysis based on winter seasons from 1991/92 to 2023/24 further identified the coupling modes that exist between Eurasian midlatitude Rossby waves and SAT over eastern China,as well as between tropical convection and precipitation over the same region.These findings suggest that the configurations of tropical and extratropical signals provide universal subseasonal predictability sources for winter snowfall over eastern China.
文摘本文对2023年12月旅顺出现的连续10天强降雪天气事件进行回顾,运用多个站点观测资料、ERA5的位势高度场、海表温度场、中央气象台的天气形势图与近10年12月连续降雪事件加以对比总结,结果表明:2023年12月平均的冷涡强度最强(中心强度为5080位势米),强大的冷涡以及极为偏东的高空冷空气堆积是此次连续降雪事件的主要系统;渤海海峡的等温线分布有一个明显的向渤海以北延伸的暖舌(5.2℃~7.6℃之间),平均海气温差在9.4℃,这样冷空气在经过上游暖舌区域增温增湿后可给辽东半岛带来冷流降雪;此次连续降雪既有系统性降雪,又有冷流性降雪,其中冷流降雪(旅顺地区风速小),850 hpa或700 hpa分别处在涡后或槽后脊前,系统性降雪,500 hpa、700 hpa我区均处于高空槽前,850 hpa处于槽后脊前;冷流降雪前及过程中,辽东半岛北部中低空都出现了明显的垂直运动、水汽输送、水汽辐合,700 hpa相较850 hpa更为明显。In this paper, the 10 consecutive days of heavy snowfall in Lvshun in December 2023 was reviewed, and the observation data of several stations, the geopotential height field of ERA5, the sea surface temperature field, and the weather situation chart of the National Meteorological Center of CMA were compared with the continuous snowfall events in December in recent 10 years. The results show that: In December 2023, the average intensity of the cold vortex is the strongest (the central intensity is 5080 geopotential meters), and the strong cold vortex and the accumulation of high altitude cold air very far to the east are the main systems of this continuous snowfall event. The isothermal distribution of the strait has an obvious warm tongue (between 5.2˚C~7.6˚C) extending to the north of the Bohai Sea, the average temperature difference between the sea and the air is 9.4˚C, so that the cold air can bring cold flow snow to the Liaodong Peninsula after warming and humidification in the upstream warm tongue area. The continuous snowfall has both systematic snowfall and cold flow snowfall, among which cold flow snowfall (low wind speed in the Lvshun area), 850 hpa or 700 hpa are behind the vortex or in front of the rear ridge of the trough, and systematic snowfall, 500 hpa and 700 hpa are in front of the upper trough, and 850 hpa is in front of the rear ridge of the trough. Before and during the cold current snowfall, there are obvious vertical movements, water vapor transport and water vapor convergence in the middle and low levels in the northern part of the Liaodong Peninsula, the phenomenon is more pronounced at 700 hpa than 850 hpa.
