Trends in frequency of precipitation extremes in the Yangtze River basin,China: 1960–2003 / Tendances d'évolution de la fréquence des précipitations extrêmes entre 1960 et 2003 dans le bassin versant du Fleuve Yangtze (Chine)     

《水文科学杂志》2013,58(3)

Abstract

The spatial distribution and trends in the frequency of precipitation extremes over the last 44 years (1960–2003), especially since 1990, have been analysed using daily precipitation data from 147 stations in the Yangtze River basin. The research results are as follows: (1) The 15 mm precipitation isohyet approximately divides the precipitation extremes (corresponding to the 95th percentile) of the stations in the middle and lower Yangtze reaches (higher) from those of the upper Yangtze reaches (lower). Also the starting time of the precipitation extremes in the middle and lower Yangtze reaches is earlier than of those in the upper Yangtze reaches. Precipitation extremes are concentrated mostly in June in the middle and lower Yangtze reaches, and July in the upper Yangtze reaches. (2) During the period 1960–2003, the first two decades had fewer precipitation extremes than the last two decades. There have been significant increasing trends and step changes in frequency of annual total precipitation extremes and precipitation extremes with a 1–5 day gap in the middle and lower Yangtze reaches. Precipitation extremes occur more frequently in shorter periods, separated by a few days. Precipitation extremes are also becoming more concentrated in the month with the highest frequency of extremes (June) in the middle and lower Yangtze reaches. In the upper Yangtze reaches, there is an upward tendency of extreme events in June. Increasing precipitation extremes in June for both the middle and lower, and the upper Yangtze reaches will increase the probability of flooding if the observed trends of the last 40 years continue into the future.  相似文献   

The Coweeta Hydrologic Laboratory and the Coweeta Long-Term Ecological Research Project     

Chelcy Ford Miniat  Andrew Christopher Oishi  Paul V. Bolstad  C. Rhett Jackson  Ning Liu  Jason P. Love  Catherine M. Pringle  Kelsey J. Solomon  Nina Wurzburger 《水文研究》2021,35(7):e14302

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Long-term thermal stability study of the typical embankment along the Qinghai-Tibet Railway in warm permafrost regions北大核心CSCD     

徐岳震  申明德  周志伟  马巍  李国玉 《冰川冻土》2022,44(6):1784-1795

Using the long-term ground temperature monitoring data of the permafrost zone along the Qinghai-Tibet Railway from 2006 to 2020,three types of typical roadbed structures were analyzed. Traditional embankment（TE）,U-shaped crushed rock embankment（UCRE）and crushed rock revetment embankment（CRRE）were included the three types of typical roadbed,which were selected to the long-term monitoring sections within the warm permafrost zones. The evolution of ground temperature field,mean annual ground temperature （MAGT）and annual maximum ground temperature（AMGT）in the depth range of 20 m under the embankment were analyzed and studied since 15 years of operation. The monitoring and analysis results show that：the growth rate of MAGT under the left and right shoulders of the TE is always higher than that of the same depth in the natural site. The MAGT under the UCRE is always lower than the natural site and always maintains a certain difference,whereas,the difference in ground temperature under the left and right shoulders is also not negligible. The MAGT of the left shoulder in the CRRE is not much different from that of the natural hole,while the MAGT of the right shoulder is always lower than that of the natural hole,and the differ in ground temperature between the left and right shoulders is smaller than that of the UCRE. The artificial permafrost table（APT）under the TE is always lower than that of in the natural site. Both the UCRE and CRRE,the APT in the left and right shoulders of them has been elevated into the embankment,and the differ of APT between the left and right shoulders is about 1. 0~1. 5 m. the differ of APT between the left and right shoulders in the CRRE is slightly lower than that of UCRE. Overall,because of the influence of thermal disturbance about engineering and climate warming,the TE in the warm permafrost zones cannot keep the thermal stability of permafrost under the embankment. Some active-cooling and reinforcement measures need to be taken. Both of the UCRE and CRRE,have a certain active-cooling effect on the permafrost under embankment,but the differ in ground temperature between the left and right shoulders still needs to be taken seriously. © 2022 Science Press (China).  相似文献   

Fractal characteristics of sand grain group changes under freeze-thaw cycles and its correlation with long-term strength北大核心CSCD     

刘启  张泽  张圣嵘  恽晴飞  付峻松 《冰川冻土》2022,44(6):1820-1832

Seasonally frozen soils are widely distributed in China in terms of area,and the freeze-thaw cycle effect generated by the alternation of cold and warmth is one of the causes of engineering damage in cold areas during construction,and it is particularly important to restore the nature and state of the soil when it is subjected to freeze-thaw action. Therefore,sandy soil specimens with different numbers of freeze-thaw cycles were prepared,and the long-term strength of frozen sandy soil was tested using a spherical template indenter. Using fractal theory and the microstructure image processing software ImageJ,the change law of grain group and long-term strength of two frozen sandy soils under different numbers of freeze-thaw cycles were studied. The results show that：for fine sand（FS）,the fractal dimension DB has a highly significant positive correlation with the long-term strength variation,among which ≥0. 15~0. 20 mm and ≥0. 25~0. 40 mm have the best fit with the long-term strength,and are the dominant grain classes of FS. For medium sand（MS）,the fractal dimension DB is slightly positively correlated with the long-term strength,and the variation shows a“vertical N”trend,in which the grain size content of ≥0. 30~0. 40 mm and ≥0. 40 mm fits better with the long-term strength,and is the dominant grain class for MS. The content of other grain groups did not correlate significantly with the long-term strength change. The freeze-thaw action changed the content ratios of coarse and fine grain agglomerates in the soil. With the increase of the overall particle size interval,the dominant particle size also increases,which shows that the long-term strength of frozen sandy soil tends to decrease and then increase with the increase of the content of some particle sizes. The results of the study can provide theoretical reference for the determination of long-term strength in areas subject to freeze-thaw action. © 2022 Science Press (China).  相似文献   

海底沉积物孔隙压力原位长期观测技术回顾和展望     

陈天  贾永刚  刘涛  刘晓磊  单红仙  孙中强 《地学前缘》2022,29(5):229-245

海底沉积物孔隙压力对海底地质灾害过程反应敏感,是表征海床稳定性的一个重要指标,通过海底沉积物的孔隙压力观测可以判断海床的稳定状态,对于海底地质灾害预测预警具有重要意义。海底沉积物孔隙压力观测存在(1)超高背景压力下的高精度测量;(2)贯入过程传感器超量程破坏;(3)系统长期供电及传感器漂移;(4)深海海底布放和回收等技术难点。国际上海底孔隙压力观测技术从20世纪60年代开始发展,逐渐形成了系列核心监测技术和成熟的商业化设备产品。挪威岩土工程研究所NGI与美国伊利诺伊大学共同研发的NGI-Illinois压差式孔隙压力观测系统,是已知最早的海底沉积物孔隙压力观测设备。此后,美国地质调查局USGS、美国桑迪亚国家实验室、英国牛津大学等相继研发了不同结构的观测设备,覆盖浅海到深海。其中,英国海洋科学研究所研发成功的深海孔隙压力原位长期观测设备PUPPI是一个重要的历史节点,该设备能够在6 000 m水深的环境中连续运行一年,成为当时最成功的海底孔隙压力观测设备,其现代化的设备结构和设计理念被后续的观测设备广为借鉴。21世纪以来,得益于海洋科学技术的整体进步,国际孔隙压力观测技术发展呈现加速趋势。法国海洋开发研究院IFREMER研发的Piezometer系列孔隙压力观测探杆,代表了当今世界的先进水平,可能是目前应用次数最多的海底孔隙压力观测设备。我国在深海探测、观测技术领域起步较晚,在深海沉积物孔隙压力原位长期观测技术方面几乎空白,发展很不成熟。其中,中国海洋大学、自然资源部第一海洋研究所等单位进行了较多的探索性研发工作。近年来,以港珠澳大桥建设、南海天然气水合物试采等为标志的大批国家级海洋建设项目如火如荼,深海油气矿产资源开发、深海天然气水合物开采利用等海洋新兴产业快速起步,深海孔隙压力原位长期监测关键核心技术等“卡脖子”问题仍然突出,严重制约了我国海洋工程产业发展的步伐。因此,迫切需要发展具有自主知识产权和关键核心技术的国产深海沉积物孔隙压力原位长期监测技术。本文回顾了国际、国内海底孔隙压力观测技术的相关研究进展,旨在分析总结孔隙压力观测技术及其应用中涉及的一些核心技术和亟待解决的关键问题,以期为我国该项技术的发展和应用提供借鉴。  相似文献   

万福煤矿不同含水率砂岩蠕变力学特性试验研究     

孙晓明  姜铭  王新波  臧金诚  高祥  缪澄宇 《岩土力学》2023,(3):624-636

为研究深部巷道围岩在地下水作用下的长期蠕变力学特性,采用自主研制的深部软岩五联流变试验系统,开展不同含水率(0%、0.8%、1.6%、2.4%、3.3%)下砂岩吸水软化单轴压缩试验及单轴蠕变试验。通过试验结果研究表明：砂岩的单轴抗压强度、弹性模量和蠕变破坏应力与含水率呈指数下降关系,蠕变破坏应力与单轴抗压强度的比值在0.76～0.84之间;砂岩衰减蠕变阶段时间随着含水率的增加而减少,随应力水平的增加而增加。径向应变比轴向应变先进入稳态蠕变阶段,破坏应力下径向应变的加速蠕变阶段开始时间要先于轴向应变;基于稳态蠕变速率曲线确定了砂岩的长期强度,径向稳态蠕变速率确定的值略小于轴向,长期强度与含水率之间满足负指数关系;将蠕变试验中径向应变与轴向应变之比定义为μ_c,提出了基于μ_c值的岩石长期强度确定方法且μ_c值与含水率无关,对于本次砂岩样品可以认为μ_c值大于0.3时样品会在一定时间内发生加速蠕变破坏;随着含水率的增加,样品破坏形态由单斜面剪切破坏逐渐演变至X状共轭斜面剪切破坏。研究结果为地下水作用下巷道长期稳...  相似文献   

Burial fluxes and sources of organic carbon in sediments of the central Yellow Sea mud area over the past 200 years     

YANG Shu  YANG Qian  LIU Sai  CAI Deling  QU Keming  SUN Yao 《海洋学报(英文版)》2015,34(10):13-22

Long-term changes of composition,sources and burial fluxes of TOC(total organic carbon) in sediments of the central Yellow Sea mud area and their possible affecting factors are discussed in this paper.Firstly,similarity analysis is employed to confirm that the carbon burial features resulted from two collected cores are typical in the central Yellow Sea mud area where YSWC(Yellow Sea Warm Current) is prevalent.On this basis,the burial flux of TOC here was considered to be 235.5–488.4 μmol/(cm2?a) since the first industrial revolution,accounting for about 70%–90% among burial fluxes of TC(total carbon) in the sediments.Compared TOC/TC ratio in the two cores with that in other marine sediments worldwide,we suggest that the growth of calcareous/non-calcareous organisms and dissolution of IC(inorganic carbon) are important factors controlling the TOC/TC ratio in sediment.Results of two-end mixed model based on δ13C data indicate that marine-derived organic carbon(OCa)is the main part among total burial organic carbon which accounts for a ratio over 85%.Due to the high TOC/TC ratio in the two cores,TC in the sediments also mainly exists as OCa,and the proportion of OCa is about 60%–80%.Away from the shore and relatively high primary production in upper waters are the main reasons that OCa is predominant among all burial OC in sediments of the central Yellow Sea mud area.Burial of OC in this mud area is probably mainly influenced by the human activities.Although the economic development during the late 19 th century caused by the first industrial revolution in China did not obviously increase the TOC burial fluxes in the sediments,the rise of industry and agriculture after the founding of new China has clearly increased the TOC burial flux since 1950 s.Otherwise,we also realize that among TC burial fluxes,TIC account for about 10%–30% in sediments of the central Yellow Sea mud area,so its burial could not be simply ignored here.Distinct from TOC burial,long-term TIC burial fluxes variations relate with climate changes more closely:the East Asian summer monsoon may influence the strength of the Huanghe River(Yellow River) flood,which could further affect the transport of terrestrial IC from land to the central Yellow Sea as well as the burial of these IC in the sediments.  相似文献   

Variations in the summer monsoon rainbands across eastern China over the past 300 years     

郝志新  郑景云  葛全胜 《大气科学进展》2009,26(4):614-620

Based on reconstructions of precipitation events from the rain and snowfall archives of the Qing Dynasty (1736–1911),the drought/flood index data mainly derived from Chinese local gazettes from 1736–2000, and the observational data gathered since 1951,the spatial patterns of monsoon rainbands are analyzed at different time scales.Findings indicate that monsoon rainfall in northern China and the middle-lower reaches of the Yangtze River have significant inter-annual(e.g.,5–7-yr and 2–4-yr)as well as inter-de...  相似文献   

西北太平洋热带气旋频数和强度变化趋势初探   总被引：4，自引：0，他引：4       下载免费PDF全文

赵珊珊  高歌  孙旭光  杨修群 《应用气象学报》2009,20(5):555-563

利用1951—2006年西北太平洋 (含南海) 热带气旋资料, 研究了不同强度热带气旋的气候变化特征。结果表明:超强台风 (近中心最大风速≥58m/s, 简称超强台风Ⅱ) 频数、强度和初、终旋日期的变化特征都不同于其他级别热带气旋; 西北太平洋热带气旋的总频数有长期减少趋势, 主要由热带低压和超强台风Ⅱ的长期减少趋势引起; 随着热带气旋强度增强, 出现月最大频数的月份逐渐推迟; 超强台风月频数最大值发生在秋季; 超强台风Ⅱ频数的年变化与除了超强台风Ⅰ(近中心最大风速为51~58m/s) 外的其他级别热带气旋反相关; 受超强台风Ⅱ减少影响, 热带气旋年平均最大风速有减小的长期趋势; 热带气旋的初、终旋日期没有显著的长期变化趋势, 但超强台风Ⅱ的初旋日期有推迟趋势, 终旋日期有提前趋势, 发生时间缩短。  相似文献   

多层位超深试验观测井施工技术          下载免费PDF全文

陶天才  石玲娣 《探矿工程》2010,37(3):24-26

鄂尔多斯盆地西南缘,白垩系志丹群的6个岩组分布俱全,地质与水文地质信息丰富。介绍了位于该区的具有勘探与长观双重意义,集全孔段取心、四层分层抽水试验、三层长期观测于一井的B5号井的井身结构设计和施工工艺。通过B5号多层位超深试验观测井的施工,证明了一井多用途的经济性和可能性,积累了多层位超深观测井施工经验,为整个鄂尔多斯盆地水文地质调查起到了示范作用。  相似文献