Variability in the vertical hyporheic water exchange affected by hydraulic conductivity and river morphology at a natural confluent meander bend          下载免费PDF全文

Jinxi Song  Guotao Zhang  Weize Wang  Qi Liu  Weiwei Jiang  Weiqiang Guo  Bin Tang  Haifeng Bai  Xinyi Dou 《水文研究》2017,31(19):3407-3420

River confluences and their associated tributaries are key morphodynamic nodes that play important roles in controlling hydraulic geometry and hyporheic water exchange in fluvial networks. However, the existing knowledge regarding hyporheic water exchange associated with river confluence morphology is relatively scarce. On January 14 and 15, 2016, the general hydraulic and morphological characteristics of the confluent meander bend (CMB) between the Juehe River and the Haohe River in the southern region of Xi'an City, Shaanxi Province, China, were investigated. The patterns and magnitudes of vertical hyporheic water exchange (VHWE) were estimated based on a one‐dimensional heat steady‐state model, whereas the sediment vertical hydraulic conductivity (K_v) was calculated via in situ permeameter tests. The results demonstrated that 6 hydrodynamic zones and their extensions were observed at the CMB during the test period. These zones were likely controlled by the obtuse junction angle and low momentum flux ratio, influencing the sediment grain size distribution of the CMB. The VHWE patterns at the test site during the test period mostly showed upwelling flow dominated by regional groundwater discharging into the river. The occurrence of longitudinal downwelling and upwelling patterns along the meander bend at the CMB was likely subjected to the comprehensive influences of the local sinuosity of the meander bend and regional groundwater discharge and finally formed regional and local flow paths. Additionally, in dominated upwelling areas, the change in VHWE magnitudes was nearly consistent with that in K_v values, and higher values of both variables generally occurred in erosional zones near the thalweg paths of the CMB, which were mostly made up of sand and gravel. This was potentially caused by the erosional and depositional processes subjected to confluence morphology. Furthermore, lower K_v values observed in downwelling areas at the CMB were attributed to sediment clogging caused by local downwelling flow. The confluence morphology and sediment K_v are thus likely the driving factors that cause local variations in the VHWE of fluvial systems.  相似文献   

Using stable isotopes to understand seasonal and interannual dynamics in moisture sources and atmospheric circulation in precipitation          下载免费PDF全文

Yu Tang  Xianfang Song  Yinghua Zhang  Dongmei Han  Likun Ai  Tianbao Zhao  Yajun Wang 《水文研究》2017,31(26):4682-4692

Stable isotopes in precipitation are useful tracers to strengthen understanding of climate change and hydrological processes. In this study, the moisture sources of 190 precipitation events in Beijing were analysed using the Hybrid Single‐particle Lagrangian Integrated Trajectory model, based on which we studied the relation between variations in precipitation δ¹⁸O and dynamics in moisture sources and atmospheric circulation in seasonal and interannual timescales. Categorization of 7 groups of moisture sources was performed, among which oceanic moisture sources presented lower δ¹⁸O in precipitation than continental moisture sources. The results show that seasonal variations of precipitation δ¹⁸O were caused by changes of moisture sources. In summer, moisture from proximal oceans dominated vapour transport to Beijing due to increasing monsoon strength and resulted in a relatively small variation of precipitation δ¹⁸O. At the interannual timescale, the variations of δ¹⁸O in summer precipitation were related to dynamics in oceanic moistures, showing depleted values when the contribution of oceanic moistures, especially the proportion of long‐distance oceanic moisture, was high. Further analysis indicated that changes of oceanic moisture sources were controlled by the strength of summer monsoons. These findings address the complexity of moisture sources in midlatitude monsoon areas and suggest that isotopic signals in precipitation have the potential to deduce changes in moisture sources and atmospheric circulation and can therefore serve for palaeoclimate reconstruction.  相似文献   

Meteorological disaster frequency at prefecture-level city scale and induced losses in mainland China during 2011–2019     

Xu  Ximeng  Tang  Qiuhong 《Natural Hazards》2021,109(1):827-844

Natural Hazards - Meteorological disasters (MDs), including drought, flood, hail, low temperature and frost (LTF), are causing severe damage to human life and economic development in China. Mapping...  相似文献   

Impact of resolution on regional climate modeling in the source region of Yellow River with complex terrain using RegCM3     

Pinhong Hui  Jianping Tang  Shuyu Wang  Jian Wu  Xiaorui Niu  Yue Kang 《Theoretical and Applied Climatology》2016,124(1-2):365-373

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In situ Measurement of Hydraulic Properties of the Fractured Zone of Coal Mines   总被引：1，自引：0，他引：1  

Zhen Huang  Zhenquan Jiang  Xin Tang  Xianshuai Wu  Dechun Guo  Zuncai Yue 《Rock Mechanics and Rock Engineering》2016,49(2):603-609

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Effects of Interface Behavior on Fracture Spacing in Layered Rock     

Xu Chang  Jianhua Wang  Chunan Tang  Zhongliang Ru 《Rock Mechanics and Rock Engineering》2016,49(5):1733-1746

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On the Thermo-Hydro-Mechanical Behaviour of a Sheared Callovo-Oxfordian Claystone Sample with Respect to the EDZ Behaviour     

Hamza Menaceur  Pierre Delage  Anh Minh Tang  Nathalie Conil 《Rock Mechanics and Rock Engineering》2016,49(5):1875-1888

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贵州辐射雾的时空变化特征及其气象要素分析     

谢清霞  唐延婧  庞庆兵 《气象与环境科学》2016,39(2):119-125

选取2008—2012年贵州省3646站次的辐射雾天气过程,根据08时能见度大小将其划分为4级雾、3级雾、2级雾和1级雾四个等级,利用常规地面观测资料分析其时空变化特征,并根据辐射雾多发生区选取出修文、三穗和凤冈3个分布在贵州省高速干道上的站点,利用相应地面气象观测台站的逐日逐时实测气象要素资料,分析其不同等级的气象要素特征。结果表明:各等级辐射雾在10月—次年1月发生较多;空间分布呈"东多西少"格局,4级雾主要分布中心为修文和岑巩,其余等级辐射雾主要分布中心为三穗、凤冈、平塘、正安、松桃和锦屏;修文站的4级雾偏多与其平均相对湿度明显偏高、风速小于3 m/s和风向主要为偏东风相关性较高;三穗站和凤冈站的平均相对湿度与当日08时和前一日20时的气温差相对利于雾的生成,但其风速较小,垂直混合较弱,故其主要为较低等级雾。  相似文献   

同化FY3B/IRAS资料对GRAPES分析场影响诊断     

王根  刘文静  唐怀瓯 《气象与环境科学》2016,39(3):15-21

GRAPES(Globe and Regional Assimilation and Prediction System)变分系统能够同化常规资料和非常规卫星资料,这些被同化的资料究竟对同化系统得到的分析场有何影响,目前国内外尚未见相关的研究文献。为此,首次采用基于信息熵信号自由度思想,诊断风云三号B星(FY3B)红外分光计(Infrared Atmospheric Sounder,IRAS)资料对GRAPES分析场的影响。诊断过程中,采用数值逼近方法,统计2012年12月24日18时到2013年1月22日00时共114个时次IRAS资料对GRAPES分析场影响,结果表明,IRAS中高层通道亮温资料对GRAPES分析场影响比地表通道20观测亮温的影响大,地表通道8和9观测亮温对分析场影响较大。前24个GRAPES变分同化时次每个时次IRAS通道亮温对分析场影响的贡献率分析结果显示,高层通道和H_2O通道贡献率较大。个例分析结果表明,在同化探空资料基础上加入IRAS资料后,温度和湿度增量场变化幅度较大,表明IRAS资料对分析场有降温和增湿作用。  相似文献   

Shield Tunneling in Rock–Soil Interface Composite Formations     

Yiqun Tang  Jie Xu 《Geotechnical and Geological Engineering》2016,34(6):1693-1705

With increased demand for the tunnel construction in rock–soil interface composite formations, the influence on surrounding environment especially the excavation face instability during construction and ground settlement in the long term has gained great attention. The researches about environmental disturbance by shield tunneling construction in single ground as the soil or rock conditions have been developed continuously. However, due to the complexity and uncertainty of the interaction between rock–soil interface composite formations and shield machines, works on these special conditions have not been carried out sufficiently. In this paper the theoretical, experimental and numerical researches on the excavation face stability and ground settlement are discussed while the in situ datum are used to support them. First, the typical projects in rock–soil interface composite formations are listed and the difficulties met are summarized. Second, the failure model of excavation face and support pressure from the tunneling shield in rock–soil interface composite formations are discussed. Then, a comprehensive survey of the factors of ground settlement during and after construction and some effective prediction models are made. Finally, the existing problems and directions for future research are introduced.  相似文献