Continuous real‐time analysis of the isotopic composition of precipitation during tropical rain events: Insights into tropical convection          下载免费PDF全文

Shaoneng He  Nathalie F. Goodkin  Dominik Jackisch  Maria Rosabelle Ong  Dhrubajyoti Samanta 《水文研究》2018,32(11):1531-1545

To investigate stable isotopic variability of precipitation in Singapore, we continuously analysed the δ‐value of individual rain events from November 2014 to August 2017 using an online system composed of a diffusion sampler coupled to Cavity Ring‐Down Spectrometer. Over this period, the average value (δ¹⁸O_Avg), the lowest value (δ¹⁸O_Low), and the initial value (δ¹⁸O_Init) varied significantly, ranging from ?0.45 to ?15.54‰, ?0.9 to ?17.65‰, and 0 to ?13.13‰, respectively. All 3 values share similar variability, and events with low δ¹⁸O_Low and δ¹⁸O_Avg values have low δ¹⁸O_Init value. Individual events have limited intraevent variability in δ‐value (Δδ) with the majority having a Δδ below 4‰. Correlation of δ¹⁸O_Low and δ¹⁸O_Avg with δ¹⁸O_Init is much higher than that with Δδ, suggesting that convective activities prior to events have more control over δ‐value than on‐site convective activities. The d‐excess of events also varies considerably in response to the seasonal variation in moisture sources. A 2‐month running mean analysis of δ¹⁸O reveals clear seasonal and interannual variability. Seasonal variability is associated with the meridional movement of the Intertropical Convergence Zone and evolution of the Asian monsoon. El Niño–Southern Oscillation is a likely driver of interannual variability. During 2015–2016, the strongest El Niño year in recorded history, the majority of events have a δ¹⁸O value higher than the weighted average δ¹⁸O of daily precipitation. δ¹⁸O shows a positive correlation with outgoing longwave radiation in the western Pacific and the Asian monsoon region, and also with Oceanic Niño Index. During El Niño, the convection centre shifts eastward to the central/eastern Pacific, weakening convective activities in Southeast Asia. Our study shows that precipitation δ‐value contains information about El Niño–Southern Oscillation and the Intertropical Convergence Zone, which has a significant implication for the interpretation of water isotope data and understanding of hydrological processes in tropical regions.  相似文献   

川西理塘断裂带奔戈- 村戈段古地震事件及其非均匀性活动特征     

张克旗  吴中海  周春景  田婷婷  李跃华  李家存 《地质学报》2020,94(4):1295-1303

在对青藏高原东南缘地区的理塘左旋走滑活动断裂带野外调查研究中,在其奔戈- 村戈段开挖了两个探槽LT1301和SLT1204。在对两个探槽上所揭示出的古地震事件进行详细划分的基础上,结合所获得的10个OSL年代样品和13个14C年代样品的测试年龄,对理塘断裂带北段的古地震事件发生时代进行了厘定。结果表明2个探槽共揭示出至少4次古地震事件,其中小规模的探槽LT1301仅揭示出1次古地震,可能为发生于公元1729年的历史地震,或是可能发生于距现在950a~1. 0ka之间的一次大地震,由于关键部位年代数据不足,上述两种可能性尚无法明确。较大的探槽SLT1204揭示出包含有探槽LT1301中古地震事件在内的古地震4次,最早的古地震事件I发生于9. 9ka之前,而事件II、III和IV则发生在公元1729年~4. 8kaBP之间,复发间隔为约1. 6ka。川西理塘断裂带北段的古地震研究结果表明,该断裂的大地震复发具有非线性特征,不符合特征地震模式,其中全新世晚期的大地震活动频率明显增大,表明它正处于丛集活动阶段。  相似文献   

不同强度冷空气对太湖水热交换的定量影响     

刘强  王伟  肖薇  荆思佳  张弥  胡勇博  张圳  谢燕红 《湖泊科学》2019,31(4):1144-1156

作为冷季主要的天气事件,冷空气过境会改变湖泊上方的气团性质,对湖泊的水热通量产生影响,进而影响湖泊的生物物理和化学过程.以亚热带大型浅水湖泊——太湖为研究对象,基于2012-2017年5个冷季（11月-翌年3月）的太湖中尺度通量网观测数据,量化不同强度冷空气（寒潮、强冷空气和较强冷空气）对太湖水热通量的影响.结果表明：在5个冷季中,寒潮、强冷空气和较强冷空气发生的总次数分别为4、11和33次,累积持续天数分别为14、31和78天.冷空气过境显著增强太湖的水热通量,3种冷空气过境使太湖的感热通量分别增至无冷空气时的10.3、6.0和4.3倍,潜热通量分别增至无冷空气时的4.0、2.1和2.7倍.虽然冷空气影响天数仅占冷季天数的16.4%,但对整个冷季的潜热和感热通量贡献分别为34.9%和51.7%,以较强冷空气贡献最大.冷空气影响时,水-气界面的温度梯度是太湖感热通量的主控因子,而潜热通量的主控因子为风速.与深水湖泊相比,太湖等浅水湖泊对冷空气过境的响应更快,寒潮过境时尤为明显.  相似文献   

A continuous modelling approach for design flood estimation on sub-daily time scale     

B. Winter  K. Schneeberger  N.V. Dung  M. Huttenlau  S. Achleitner  J. Stötter 《水文科学杂志》2019,64(5):539-554

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喜马拉雅地区与天山地区地壳强地震的孕震因素探讨     

陈应君 《中国地震》2019,35(2):305-318

利用哈佛大学GCMT数据中心和前人积累的历史地震资料(1962~2016年M W>4.0地震)以及Crust2.0地壳结构统计分析了喜马拉雅地区、天山地区的地壳区域构造与地震活动间的相关性。此外,利用GFZ地学研究中心提供的静态卫星重力模型GGM03S/EGM2008和地形模型Topo计算了2个地区的各类重力异常场,同时还模拟了不同地壳弹性参数下的重力异常场,结果表明喜马拉雅地区重力异常场在水平、垂直方向的梯度特征远大于天山地区的异常特征,且喜马拉雅地区的有效弹性板厚度Te(6~15km)小于天山地区的有效弹性板厚度Te(20~30km)。最后,利用喜马拉雅地区与天山地区的GPS震间三维形变场约束了断层运动模型,结果显示两者主前缘断裂的断层闭锁深度及应力积累状态存在较大的差异。因此认为,造成青藏高原及邻区的边界地壳区域地震活动性差异的动力学因素,与地壳有效弹性板厚度、孕震断层参数及区域应力积累状态等密切相关。  相似文献   

The Kellwasser events in the Upper Devonian Frasnian to Famennian transition in the Toc Tat Formation,northern Vietnam     

Toshifumi Komatsu  Ryota Urakawa  Toshitaka Inada  Kazuki Yamauchi  Takumi Maekawa  Reishi Takashima  Mark Williams  Phong D. Nguyen  Hung D. Doan  Minh T. Nguyen  Shuji Niko  Gengo Tanaka  Tatsuhiko Yamaguchi 《Island Arc》2019,28(1)

Upper Devonian carbonates of the Toc Tat Formation in the Si Phai Pass area of Dong Van District, northern Vietnam were deposited in carbonate platform, slope, and basin environments. These carbonates yield abundant conodonts indicative of the Palmatolepis nasuta, Pa. linguiformis and Pa. triangularis zones, the Frasnian–Famennian stage boundary being identified by the first occurrence of Pa. triangularis. Two positive carbon isotope excursions are recognized, the lower excursion peaking in the interval of the lower to middle Pa. nasuta Zone, whilst the upper excursion peaks just above the local Frasnian–Famennian boundary. Based on the biostratigraphy, these excursions equate to the Lower and Upper Kellwasser events. Locally, tentaculitoid taxa (Nowakia, Styliolina, Homoctenus, and Metastyliolina?) are abundant in the interval of the Pa. nasuta Zone, but show a drastic decline in abundance before the Lower Kellwasser Event, and only two taxa survived into the Famennian.  相似文献   

基于波形特征的露天钼矿微震事件的识别分析——以卓资山钼矿为例     

赵艳红  包金哲  王树波  翟浩  魏建民  杨智升  张晖  赵铁锁  苏日亚  王磊  王鑫  贾昕晔  刘芳 《震灾防御技术》2019,14(3):662-676

基于前人研究成果以及现场的实测结果,采用卓资山露天钼矿微震监测项目产出资料,提取了5类微震事件的波形特征和时频特征。波形特征显示:微地震的振幅、辐射均匀性和频率变化特征表明微地震是由于岩层受到单力偶和剪切力作用破裂而产生;爆破具有P波初动方向向上、S波不易识别的特点,包含“初震段、主震段、尾波段”三段变化形态;小型边坡滑坡波事件属楔体滑坡,是由多个“加速—缓冲—终止”构成,波形是由包络线呈“V”字形的多组脉冲波列组成;机械开采震动事件具有自振能量不变、脉冲幅度相差很大、持续时间间隔不确定的特点;运输车辆波形振幅具有形态“弱—强—弱”、等频率、包络线呈多段纺锤形的特征。时频空间分布可以分为相对独立、界限分明的两类:一类包含微地震、爆破、机械开采、小型边坡滑坡事件,另一类只包含车辆运输事件。  相似文献   

Late Holocene floodplain incision and alluvial fan formation in the central Grampian Highlands,Scotland: chronology,environment and implications     

Colin K. Ballantyne  Graeme Whittington 《第四纪科学杂志》1999,14(7):651-671

A section cut across an alluvial fan and the underlying floodplain terrace in the central Grampian Highlands provides an unusually complete record of late Holocene events. At ca. 2.7–2.4 cal kyr BP floodplain aggradation was replaced by net floodplain incision. Pollen evidence and charcoal counts provide no evidence for contemporaneous anthropogenic landscape change, and the timing of the transition suggests that it reflects an increase in high-magnitude erosive flood events following overall climatic deterioration. The overlying fan was deposited by torrential hyperconcentrated flows during three brief storm-generated depositional events at ca. 2.2–2.1, 1.9–1.8 and 0.9–0.7 cal kyr BP, separated and succeeded by prolonged periods of stability and peat accumulation. During these three events, a cumulative total of ca. 6750 m³ of sediment was deposited, probably in no more than a few hours over a timescale of two millennia. These findings imply that proposed links between human activity and the development of alluvial fans or debris cones require reassessment, and that different elements of the Holocene alluvial landscape have responded in different ways to the same climatic inputs. Aggregation of dating evidence relating to aggradation or incision of alluvial landforms at different scales therefore may produce misleading results. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

‘Bond cycles’ recorded in terrestrial Pleistocene sediments of southwestern British Columbia,Canada     

Stephen R. Hicock  Olav B. Lian  Rolf W. Mathewes 《第四纪科学杂志》1999,14(5):443-449

Recent data from exposures of terrestrial Pleistocene sediments in the Fraser Lowland of southwestern British Columbia reveal at least two ‘Bond cycles’ within Oxygen Isotope Stage 2. The maximum of the Coquitlam Stade coincides with the timing of Heinrich event H2, the Port Moody Interstade with Dansgaard–Oeschger (D–O) interstade 2, the maximum of the Vashon Stade with H1, and the Fort Langley interval with D–O interstade 1. The Sumas Stade apparently preceded H0 (Younger Dryas) but could have been in response to the same climatic signal. The timing of Sumas advances may be explained by a combination of glacio-isostatic rebound, destabilisation of the ice margin, and rapid movement over a short distance on soft muddy beds of a rising sea floor, thereby leading the timing of North Atlantic events by hundreds of years. In contrast, Coquitlam and Vashon advances were mainly over permeable glaciofluvial sediments and because of this their maxima probably did not precede the timing of H2 and H1. The Port Moody Interstade coincided with the global Last Glacial Maximum, due in part to the moderating effect of moist summer storms in a southward-shifted jet stream that influenced the Fraser Lowland at that time. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

太阳质子事件耀斑的短期预报   总被引：1，自引：0，他引：1  

王家龙 《中国天文和天体物理学报》1999,(4)

回顾产生太阳质子事件耀斑的短期预报,讨论短期预报在近期应做的研究．给出以下结论：（１）在６０年代和７０年代,质子事件耀斑的预报有相当大的进展;（２）新预报方法的探索和质子流在日冕与行星际的传播问题,是当前改进短期预报的关键;（３）对实际应用的短期预报工作的改进,可能需要从空间天气预报的角度,研究太阳活动区的分类．  相似文献