利用地面气象观测站资料、加密地面观测资料和欧洲中期天气预报中心(European Centre for Medium-Range Weather Forecasts, ECMWF)第五代大气再分析数据(ECMWF Reanalysis v5,ERA5;分辨率为0.25°×0.25°)逐小时资料,对山...利用地面气象观测站资料、加密地面观测资料和欧洲中期天气预报中心(European Centre for Medium-Range Weather Forecasts, ECMWF)第五代大气再分析数据(ECMWF Reanalysis v5,ERA5;分辨率为0.25°×0.25°)逐小时资料,对山东2021年11月6—8日极端暴雪过程雪水比影响因子进行研究。结果显示:此次暴雪过程平均雪水比分布总体呈“北大南小、西大东小”的分布特征,降雪初期产生的雪水比小,降雪中后期产生的雪水比大;温度偏高、云内液态水含量较高的地区雪水比较小,温度偏低、云内液态水含量较低的地区雪水比较大;雪水比与地面气温、地表温度呈负相关,地面气温与雪水比的相关性最大,积雪产生之后地表温度与雪水比变化无明显相关。展开更多
Extreme snowfall events over the Tibetan Plateau(TP)cause considerable damage to local society and natural ecosystems.In this study,the authors investigate the projected changes in such events over the TP and its surr...Extreme snowfall events over the Tibetan Plateau(TP)cause considerable damage to local society and natural ecosystems.In this study,the authors investigate the projected changes in such events over the TP and its surrounding areas based on an ensemble of a set of 21st century climate change projections using a regional climate model,RegCM4.The model is driven by five CMIP5 global climate models at a grid spacing of 25 km,under the RCP4.5 and RCP8.5 pathways.Four modified ETCCDI extreme indices-namely,SNOWTOT,S1mm,S10mm,and Sx5day-are employed to characterize the extreme snowfall events.RegCM4 generally reproduces the spatial distribution of the indices over the region,although with a tendency of overestimation.For the projected changes,a general decrease in SNOWTOT is found over most of the TP,with greater magnitude and better cross-simulation agreement over the eastern part.All the simulations project an overall decrease in S1mm,ranging from a 25%decrease in the west and to a 50%decrease in the east of the TP.Both S10mm and Sx5day are projected to decrease over the eastern part and increase over the central and western parts of the TP.Notably,S10mm shows a marked increase(more than double)with high cross-simulation agreement over the central TP.Significant increases in all four indices are found over the Tarim and Qaidam basins,and northwestern China north of the TP.The projected changes show topographic dependence over the TP in the latitudinal direction,and tend to decrease/increase in low-/high-altitude areas.展开更多
利用常规观测、积雪深度逐时加密观测资料和欧洲中期天气预报中心(European Centre for Medium-Range Weather Forecasts,ECMWF)第五代大气再分析(ECMWF Reanalysis v5,ERA5)资料,对2023年12月13—15日山东一次极端暴雪天气过程积雪特...利用常规观测、积雪深度逐时加密观测资料和欧洲中期天气预报中心(European Centre for Medium-Range Weather Forecasts,ECMWF)第五代大气再分析(ECMWF Reanalysis v5,ERA5)资料,对2023年12月13—15日山东一次极端暴雪天气过程积雪特征及其成因进行分析,得到以下结论:(1)此次过程是一次江淮气旋暴雪天气过程,具有持续时间长、降水相态复杂、基础温度低、降温幅度大和积雪深度厚等特征。(2)最大小时新增积雪深度可达8 cm;过程平均雪水比为0.7 cm·mm^(-1),呈“西大东小”的分布特征。(3)有积雪的站近地面温度从开始降雪到地面产生积雪,气温和雪面温度均呈下降趋势,0 cm地温在降雪前期降温明显,积雪形成后地温不再明显变化。无积雪的站在整个降雪时段内近地面温度可分为4种情况。(4)雪水比随气温变化最明显;积雪形成之后地温对雪水比大小影响不大;当雪水比小于0.75 cm·mm^(-1)时,雪水比随雪面温度降低而增大,当雪水比大于0.76 cm·mm^(-1)后,雪面温度不再有明显变化。展开更多
Snow is important in Türkiye especially in the mountainous eastern areas where it may stay on the ground for more than half of the year.This region plays a vital role in feeding the water resources of the trans-b...Snow is important in Türkiye especially in the mountainous eastern areas where it may stay on the ground for more than half of the year.This region plays a vital role in feeding the water resources of the trans-boundary Euphrates-Tigris Basin,supporting crucial dams for water supply,irrigation and energy production.Thus,easy,frequent,correct and economical ways of measuring the snowpack is crucial.The snow properties at specific locations in the mountainous eastern regions over the two snow seasons(2018 and 2019)were studied by using different instruments and techniques,snow pit(box/cylinder/wedge cutter types),snow tube(Federal Sampler)and SnoTel(Snowpack Analyzer).The results point out a 1.7%-7.1%variation between different cutter type snow density measurements within snow pit analysis and the long-term utilized snow tube observations show a closer relation to box/cylinder type cutters.As for the continuous SnoTel observations,a variation of 2.4%-9.8%with various cutter types and a 5.9%difference regarding the snow tube density results are detected.These findings indicate a close range among different instruments,but it is the best when all three systems complement each other to characterize the snowpack effectively in the complex terrain since each has its own advantages.展开更多
An average of eight snowfall events occur each year in the eastern Lesotho Highlands.These snowfall events are typically associated with cut-off low(CoLs)systems and mid-latitude cyclones.However,the moisture sources ...An average of eight snowfall events occur each year in the eastern Lesotho Highlands.These snowfall events are typically associated with cut-off low(CoLs)systems and mid-latitude cyclones.However,the moisture sources of the snowfall are unclassified and unclear.The Hybrid Single-Particle Lagrangian Integrated Trajectory(HYSPLIT)model,an air mass back trajectory model,has been used to evaluate moisture source waters locally in southern Africa and internationally in China and Europe.This study uses HYSPLIT to determine the source moisture of snow in Lesotho.A list of all 82 snowfall events in Lesotho spanning 2017 to 2022 was compiled using the Snow Report SA Instagram page,including the date and location of snowfall.A 72-hour back trajectory for each snowfall event was initiated for both Afriski and the whole of Lesotho.This amounts to models of moisture source trajectories for 28 and 82 snowfall days,respectively.These air mass pathways are classified according to their frequency per snowfall event,per month in the snow season,per year and for the full period.From this,associated moisture source regions and dominant air mass trajectories were identified.This study reports that the air mass trajectories associated with Afriski and Lesotho as a whole are very similar.The most common pathway of air mass trajectories transporting snow-bearing moisture to Lesotho was an inland trajectory from the northern regions of southern Africa.This pathway makes up 16.6%of all trajectories reported and is associated with the Angola Low,the Congo Air Boundary and the St.Helena High Pressure.展开更多
Based on the data of daily snowfall and weather phenomena of 11 national meteorological stations in Ulanqab City from 1991 to 2020,the spatial and temporal distribution characteristics of snowstorm were analyzed.The r...Based on the data of daily snowfall and weather phenomena of 11 national meteorological stations in Ulanqab City from 1991 to 2020,the spatial and temporal distribution characteristics of snowstorm were analyzed.The results show that the snowstorm in Ulanqab had obvious seasonal distribution characteristics,mainly happening in spring(March-May)and autumn(September-November).It also had obvious regional distribution in space,and the snowstorm center appeared in Chahar Right Wing Middle Banner and Jining District,namely the east side of the Yinshan Mountain.In the past 30 years,the amount of snowstorm in the whole year in Ulanqab showed a certain fluctuation trend,and the number of snowstorm days had shown an obvious upward trend since 2011.展开更多
文摘利用地面气象观测站资料、加密地面观测资料和欧洲中期天气预报中心(European Centre for Medium-Range Weather Forecasts, ECMWF)第五代大气再分析数据(ECMWF Reanalysis v5,ERA5;分辨率为0.25°×0.25°)逐小时资料,对山东2021年11月6—8日极端暴雪过程雪水比影响因子进行研究。结果显示:此次暴雪过程平均雪水比分布总体呈“北大南小、西大东小”的分布特征,降雪初期产生的雪水比小,降雪中后期产生的雪水比大;温度偏高、云内液态水含量较高的地区雪水比较小,温度偏低、云内液态水含量较低的地区雪水比较大;雪水比与地面气温、地表温度呈负相关,地面气温与雪水比的相关性最大,积雪产生之后地表温度与雪水比变化无明显相关。
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences[grant number XDA2006040102]the National Natural Science Foundation of China[grant number 42175037].
文摘Extreme snowfall events over the Tibetan Plateau(TP)cause considerable damage to local society and natural ecosystems.In this study,the authors investigate the projected changes in such events over the TP and its surrounding areas based on an ensemble of a set of 21st century climate change projections using a regional climate model,RegCM4.The model is driven by five CMIP5 global climate models at a grid spacing of 25 km,under the RCP4.5 and RCP8.5 pathways.Four modified ETCCDI extreme indices-namely,SNOWTOT,S1mm,S10mm,and Sx5day-are employed to characterize the extreme snowfall events.RegCM4 generally reproduces the spatial distribution of the indices over the region,although with a tendency of overestimation.For the projected changes,a general decrease in SNOWTOT is found over most of the TP,with greater magnitude and better cross-simulation agreement over the eastern part.All the simulations project an overall decrease in S1mm,ranging from a 25%decrease in the west and to a 50%decrease in the east of the TP.Both S10mm and Sx5day are projected to decrease over the eastern part and increase over the central and western parts of the TP.Notably,S10mm shows a marked increase(more than double)with high cross-simulation agreement over the central TP.Significant increases in all four indices are found over the Tarim and Qaidam basins,and northwestern China north of the TP.The projected changes show topographic dependence over the TP in the latitudinal direction,and tend to decrease/increase in low-/high-altitude areas.
基金supported by the Scientific Research Project(BAP)of Eskişehir Technical University,project number 1610F676.
文摘Snow is important in Türkiye especially in the mountainous eastern areas where it may stay on the ground for more than half of the year.This region plays a vital role in feeding the water resources of the trans-boundary Euphrates-Tigris Basin,supporting crucial dams for water supply,irrigation and energy production.Thus,easy,frequent,correct and economical ways of measuring the snowpack is crucial.The snow properties at specific locations in the mountainous eastern regions over the two snow seasons(2018 and 2019)were studied by using different instruments and techniques,snow pit(box/cylinder/wedge cutter types),snow tube(Federal Sampler)and SnoTel(Snowpack Analyzer).The results point out a 1.7%-7.1%variation between different cutter type snow density measurements within snow pit analysis and the long-term utilized snow tube observations show a closer relation to box/cylinder type cutters.As for the continuous SnoTel observations,a variation of 2.4%-9.8%with various cutter types and a 5.9%difference regarding the snow tube density results are detected.These findings indicate a close range among different instruments,but it is the best when all three systems complement each other to characterize the snowpack effectively in the complex terrain since each has its own advantages.
基金the University of the Witwatersrand Friedel Sellschop Grantthe WitsUCL strategic partnership grant
文摘An average of eight snowfall events occur each year in the eastern Lesotho Highlands.These snowfall events are typically associated with cut-off low(CoLs)systems and mid-latitude cyclones.However,the moisture sources of the snowfall are unclassified and unclear.The Hybrid Single-Particle Lagrangian Integrated Trajectory(HYSPLIT)model,an air mass back trajectory model,has been used to evaluate moisture source waters locally in southern Africa and internationally in China and Europe.This study uses HYSPLIT to determine the source moisture of snow in Lesotho.A list of all 82 snowfall events in Lesotho spanning 2017 to 2022 was compiled using the Snow Report SA Instagram page,including the date and location of snowfall.A 72-hour back trajectory for each snowfall event was initiated for both Afriski and the whole of Lesotho.This amounts to models of moisture source trajectories for 28 and 82 snowfall days,respectively.These air mass pathways are classified according to their frequency per snowfall event,per month in the snow season,per year and for the full period.From this,associated moisture source regions and dominant air mass trajectories were identified.This study reports that the air mass trajectories associated with Afriski and Lesotho as a whole are very similar.The most common pathway of air mass trajectories transporting snow-bearing moisture to Lesotho was an inland trajectory from the northern regions of southern Africa.This pathway makes up 16.6%of all trajectories reported and is associated with the Angola Low,the Congo Air Boundary and the St.Helena High Pressure.
文摘Based on the data of daily snowfall and weather phenomena of 11 national meteorological stations in Ulanqab City from 1991 to 2020,the spatial and temporal distribution characteristics of snowstorm were analyzed.The results show that the snowstorm in Ulanqab had obvious seasonal distribution characteristics,mainly happening in spring(March-May)and autumn(September-November).It also had obvious regional distribution in space,and the snowstorm center appeared in Chahar Right Wing Middle Banner and Jining District,namely the east side of the Yinshan Mountain.In the past 30 years,the amount of snowstorm in the whole year in Ulanqab showed a certain fluctuation trend,and the number of snowstorm days had shown an obvious upward trend since 2011.
