Coupled Model of Two-phase Debris Flow, Sediment Transport and Morphological Evolution

The volume fraction of the solid and liquid phase of debris flows,which evolves simultaneously across terrains,largely determines the dynamic property of debris flows. The entrainment process significantly influences the amplitude of the volume fraction. In this paper,we present a depth-averaged two-phase debris-flow model describing the simultaneous evolution of the phase velocity and depth,the solid and fluid volume fractions and the bed morphological evolution. The model employs the Mohr–Coulomb plasticity for the solid stress,and the fluid stress is modeled as a Newtonian viscous stress. The interfacial momentum transfer includes viscous drag and buoyancy. A new extended entrainment rate formula that satisfies the boundary momentum jump condition(Iverson and Ouyang,2015) is presented. In this formula,the basal traction stress is a function of the solid volume fraction and can take advantage of both the Coulomb and velocity-dependent friction models. A finite volume method using Roe's Riemann approximation is suggested to solve the equations. Three computational cases are conducted and compared with experiments or previous results. The results show that the current computational model and framework are robust and suitable for capturing the characteristics of debris flows.     

Fifteen Years of Ocean Observations with China Argo

For 15 years since the beginning of China Argo project, China has deployed over 350 profiling floats in Pacific and Indian ocean, and constructed China Argo ocean observing network. Moreover, we have setup the Argo data receiving, processing and distributing system, and developed various Argo data products using Argo observations, which has promoted the progress of ocean data sharing in China. The abundant Argo data have become a main data source in oceanic and atmospheric basic researches and operational applications. A batch of important achievements in basic research and operational application have been brought, e.g. in aspects of tropical cyclone (typhoon), ocean circulation, meso-scale eddy, turbulence, heat/salt storage and transport and water mass, as well as in ocean, atmosphere/climate operational forecasting and predicting. With the extension of the international Argo program from “Core Argo” to “Global Argo”, we are faced with great challenges in the long-term maintaining and sustained developing of our Argo ocean observing network. It is suggested that we should take the opportunity to construct China regional Argo ocean observing network as soon as possible in adjacent northwestern Pacific and Indian ocean using Chinese BeiDou profiling floats, which will make us to take responsibility and obligation of a big country for addressing global climate changes and preventing natural disasters.     

Regional debris flow susceptibility analysis based on principal component analysis and self-organizing map: a case study in Southwest China

A method was developed to analyze the susceptibilities of 541 regional basins affected by debris flows at the Wudongde Dam site in southwest China. Determining susceptibility requires information on source material quantity and occurrence frequency. However, the large number of debris flows can hinder the individual field investigation in a each small basin. Factors that may trigger debris flows can be identified using remotely sensed interpretation information. Susceptibility analysis can then be conducted based on these factors. In this study, SPOT5 satellite imagery, digital elevation models (DEM), a lithology distribution map, and rainfall monitoring data were used to identify 12 debris flow trigger factors: basin relief ratio, slope gradient in the initiation zone, drainage density, downslope curvature of the main channel, vegetation coverage, main channel aspect, topographic wetness index, Melton’s ruggedness number, lithology, annual rainfall, form factor, and cross-slope curvature of the transportation zone. Principal component analysis was used to obtain the eight principal components of these factors that contribute to susceptibility results. Then, a self-organizing map method was adopted to analyze the principal components, which resulted in a debris flow susceptibility classification. Field validation of 26 debris flow basins was used to evaluate the errors of the susceptibility classification, as well as assess the causes of such errors. The study found that principle component analysis and self-organizing map methodologies are good predictors of basin susceptibility to debris flows.     

基于波形重定技术的杭州湾平均海面高模型建立

利用AVISO提供的SARAL卫星杭州湾周年的WAVEFORM数据,通过对卫星波形分析,提出了一种新的波形重定方法,该方法在顾及波形物理机制基础上,根据各波形的特征进行重定。对重定前后的波形数据进行粗差剔除、共线平均,分析了重定后数据质量。通过交叉点平差,结合验潮站数据建立杭州湾平均海面高模型,所建模型与验潮站平均海面高差值的平均值为0.006m,标准差为0.038m。结果表明,利用本文提出的方法能显著提高卫星测高数据的精度与质量。     

基于模型试验的泥石流坡面物源启动预警模型

为进一步探明银洞子沟物源区坡面物源启动机理与降雨的相关性,在进行详细的现场考察与工程勘察工作后选取了典型模型体,并采用20余组人工降雨物理试验方法将降雨强度与坡度设为控制变量,研究了4种坡形、5种雨强条件下,坡面松散物源的失稳机制及破坏模式。试验结果揭示了地表变形与地下物理力学参数变化的定量响应关系,并基于试验发生破坏的临界雨量,建立了银洞子沟传统I-D预警模型。之后提炼可靠预警参数(坡度、深部体积含水率),通过数学回归分析方法并采用Exponential模型,得出IGD、IGM多参数新型预警判别式,实现了传统I-D模型的有效修正,并具一定的可靠性和实用价值。     

Objective Analysis on Large-scale Circulation Type and Its Links to Precipitation over China

Atmospheric circulation anomaly is a direct cause of weather and climate change. In the past, most researches for the relationship between Weather Type (WT) and precipitation have mainly focused on the subjective classification and diagnosis. Compared to the subjective analysis, objective classification uses more consistent index and standard unification, thus, we can get more WTs, and it has been widely used in many areas. By using daily 12UTC Sea Level Pressure (SLP), Precipitable Water (PW), and 700 hPa wind speed (UV700) data from ECMWF’s Interim Reanalysis, the classification of WTs over China was performed with the method of obliquely rotated T-mode principle component analysis. WT and its link to precipitation over China were further analyzed. The results show that the influence of different WTs on precipitation is not uniform over China, and also show distinctly difference in different seasons. A common feature is that WTs great impact on the regions and months with large precipitation, while less impact on regions and months have with less precipitation. In addition, precipitation trends originating from WT intensity changes are much more deterministic, significant, and predictable than trends from WT frequency changes.     

月表构造与深部构造的关系

地球和月球很可能是通过大撞击形成的。在行星地质学中,研究月球的地质-构造现象,对了解月球、地球乃至太阳系的形成与演化历史都有很大帮助。月球的构造分为深部构造与月表构造,寻找它们在分布或成因上的关系,可以为月球甚至地月系的起源和演化历史提供重要参考。利用LROC的宽视角影像数据以及LOLA数据提取解译月表构造,结合深大断裂进行观察分析,并对月球的撞击盆地进行统计,最后以静海地区为例分析构造分布特征,发现月球的质量瘤盆地中具有环状分布的月岭,外侧具有近环状分布的深大断裂,自前酒海纪至酒海纪,具备上述特征的质量瘤盆地占总撞击盆地的比例突然有一个很大的提升,且静海地区西部具有该构造分布特征。推测该特征与撞击、月海沉降等有关,且在酒海纪与雨海纪期间月球有较多的月海玄武岩分布,由此判断静海西部存在质量瘤,发生过撞击与月海沉降。     

柴达木盆地那棱格勒河及其尾闾盐湖锂成矿物源：来自水化学和锶、硫同位素证据

柴达木盆地那棱格勒河尾闾盐湖（一里坪干盐滩、东台吉乃尔盐湖、西台吉乃尔盐湖和察尔汗盐湖别勒滩区段）赋存了我国目前最大的卤水锂矿床。那棱格勒河及其尾闾盐湖锂的物源仍存在一定争议,主要有围岩风化、古湖残留、含盐系地层淋滤、油田水、深部水等,目前缺乏有力的地球化学证据。本文系统采集了那棱格勒河流域及其尾闾盐湖不同水体样品16件,分析了其主、微量元素含量及锶、硫同位素组成。结合前人的研究成果,对区域水体中锂的来源进行了探讨,得出结论如下：那棱格勒河水锂含量（0. 45~0. 79 mg/L）比楚拉克阿拉干河支流（0. 00~0. 05 mg/L）高出一个数量级,其高锂含量主要受洪水河支流的补给;洪水河高锂含量与其上游热泉水的补给有关,该热泉水锂、锶含量高、 87 Sr/ 86 Sr比值偏高, δ 34 S值偏低,与青藏高原典型热泉水地球化学特征（锂含量0. 4~34. 8 mg/L,锶含量0. 07~4. 24 mg/L, 87 Sr/ 86 Sr比值0. 71224~0. 71259, δ 34 S值- 10. 6‰~7. 6‰）较一致。那棱格勒河水（0. 71170）和尾闾盐湖卤水（0. 71143~0. 71156）相似的 87 Sr/ 86 Sr比值,以及研究区河、湖水硫同位素组成符合主要蒸发浓缩过程 δ 34 S值逐渐下降的变化趋势,均证明研究区尾闾盐湖卤水锂资源主要受那棱格勒河的补给;而古湖残留水、盆地西部含盐系地层淋滤水或油田水具有明显不同的水化学特征和锶、硫同位素组成,这些水体对研究区尾闾盐湖锂补给的贡献较小,可忽略不计。     

朱溪矿集区黑云母石英二长斑岩年代学、地球化学特征及其地质意义

朱溪矿集区内新发现高Sr/Y型枣林黑云母石英二长斑岩,对其开展系统的地球化学和年代学研究,表明岩石具有高w(SiO2)(68.67％～69.27％)、高w(Al2O3)(15.78％～16.54％)、高w(K2O)(3.69％～3.88％),为高钾钙碱性、过铝质石英二长斑岩;∑REE为205.21×10-6～213.13×10-6,∑LREE/∑HREE=19.10～20.93,轻重稀土元素分馏明显,具弱Eu负异常;Ba、U、K、Pb、Sr正异常,Nb、Ta、P、Ti负异常,具岛弧岩浆特点;较高的w(Sr)(366.05×10-6～474.16×10-6)、较低的w(Y)(7.26×10-6～8.89×10-6)、w(Yb)(0.62×10-6～0.73×10-6)显示出埃达克质岩特征.锆石U-Pb年龄为(157±1)Ma.文章认为枣林黑云母石英二长斑岩受古太平洋板块向大陆斜低角度俯冲的影响,形成于弧岩浆构造环境,源区残留相以角闪岩相为主,次为石榴子石,来源深度较深.朱溪矿集区在160 Ma具备形成含Cu成矿岩浆的构造环境及岩浆岩条件,具有找寻斑岩型铜矿的潜力.     

中国西部寒区流域冰川水文调节功能研究

冰川作为固体水库以“削峰填谷”的形式显著调节径流丰枯变化,冰川的水文调节功能对于中国西北干旱区至关重要。使用现有VIC-CAS模型模拟得到中国西部寒区2014—2100年径流预估数据,从趋势和波动变化相结合的视角,基于径流变差系数法,构建了冰川水文调节指数（Glacier_R）,分析了9个寒区流域冰川径流变化的稳定性,详细剖析了历史时期（1971—2010年）和未来到21世纪末这些流域冰川水文调节功能的强弱变化。结果表明：历史时期及RCP2.6和RCP4.5情景下,除长江流域外,青藏高原其余流域的冰川径流减小时间节点为2020s,西北内陆河流域则为2010s。历史时期及RCP2.6和RCP4.5情景下至21世纪末,尽管西部寒区大部分流域的冰川径流呈减少趋势,但波动幅度减小或无明显变化,冰川径流稳定性增强或无变化。总体上,西北内陆河流域的冰川水文调节功能较高,青藏高原流域的冰川水文调节功能较低。RCP2.6和RCP4.5情景下,至21世纪末,西部寒区各流域冰川水文调节功能均呈现减弱趋势,西北内陆河流域减弱更加显著,如RCP4.5情景下,木扎提河冰川水文调节功能降幅达25.4%,而青藏高原各流域的冰川水文调节功能一直处于较低水平。从年代际变化来看,1970s—2010s是寒区流域冰川水文调节功能较强的时期,1980s和2000s两个时段冰川水文调节功能尤强;RCP2.6和RCP4.5情景下,未来到21世纪末,冰川调节功能明显减弱。减弱的时间节点不同,最早为1970s,最晚为2020s。