Identification of factors influencing hydrologic model performance using a top-down approach in a large number of U.S. catchments     

Carolina Massmann 《水文研究》2020,34(1):4-20

Investigating the performance that can be achieved with different hydrological models across catchments with varying characteristics is a requirement for identifying an adequate model for any catchment, gauged or ungauged, just based on information about its climate and catchment properties. As parameter uncertainty increases with the number of model parameters, it is important not only to identify a model achieving good results but also to aim at the simplest model still able to provide acceptable results. The main objective of this study is to identify the climate and catchment properties determining the minimal required complexity of a hydrological model. As previous studies indicate that the required model complexity varies with the temporal scale, the study considers the performance at the daily, monthly, and annual timescales. In agreement with previous studies, the results show that catchments located in arid areas tend to be more difficult to model. They therefore require more complex models for achieving an acceptable performance. For determining which other factors influence model performance, an analysis was carried out for four catchment groups (snowy, arid, and eastern and western catchments). The results show that the baseflow and aridity indices are the most consistent predictors of model performance across catchment groups and timescales. Both properties are negatively correlated with model performance. Other relevant predictors are the fraction of snow in the annual precipitation (negative correlation with model performance), soil depth (negative correlation with model performance), and some other soil properties. It was observed that the sign of the correlation between the catchment characteristics and model performance varies between clusters in some cases, stressing the difficulties encountered in large sample analyses. Regarding the impact of the timescale, the study confirmed previous results indicating that more complex models are needed for shorter timescales.  相似文献   

Evaluating soil moisture estimation from ground-penetrating radar hyperbola fitting with respect to a systematic time-domain reflectometry data collection in a boreal podzolic agricultural field     

Chameera Illawathure  Gary Parkin  Sébastien Lambot  Lakshman Galagedara 《水文研究》2020,34(6):1428-1445

The upper 30 cm of the soil profile, which hosts the majority of the root biomass, can be considered as the shallow agricultural root zone of most temperate crops. The electromagnetic wave velocity in the soil obtained from reflection hyperbolas in ground-penetrating radar (GPR) data can be used to estimate soil moisture (SM). Finding shallow hyperbolas in a radargram and minimizing the subjective error associated with the hyperbola fitting are the main challenges in this approach. Nevertheless, we were motivated by the recent improvements of hyperbola fitting algorithms, which can reduce the subjective error and processing time. To overcome the difficulty of finding very shallow hyperbolas, we applied the hyperbola fitting method to reflections ranging from 27- to 50-cm depth using a 500-MHz centre-frequency GPR and compared the estimated moisture with vertically installed, 30-cm-long time-domain reflectometry (TDR) sensors. We also compared TDR and GPR sample areas in a 2-D plane using different GPR survey types and different hyperbola depths. SM measured with TDR and GPR were not significantly different according to Mann–Whitney's test. Our analyses showed that a root mean square error of 0.03 m³ m⁻³ was found between the two methods. In conclusion, the proposed method might be suitable to estimate SM with an acceptable accuracy within the root zone if the soil profile is fairly uniform within the application depth range.  相似文献   

剪切波分裂揭示的青藏高原上地壳地震各向异性基本特征          下载免费PDF全文

郭铁龙  高原 《地球物理学报》2020,63(3):1085-1103

青藏高原整体隆升,构造运动与介质变形强烈,然而由于地震观测数据不足,青藏高原内部上地壳各向异性研究一直是一个空白.本研究使用西藏地区的地震台网(2009年5月—2017年5月)的观测资料,利用剪切波分裂研究青藏高原上地壳地震各向异性特征.由于青藏高原固定地震台站分布稀疏,可用于进行剪切波分裂研究的近场地震事件记录稀少,本研究采用地震事件的单台定位技术,对公开的地震目录里没有震源深度数据的地震事件进行震源位置约束,并引入微震模板匹配定位方法,对连续地震波形进行检索,识别出地震目录里遗漏的新的微震(小地震)事件波形.微震识别获得的新地震事件记录是地震目录里报告的地震事件记录的大约6倍,用于补充研究区的剪切波分裂数据分析.通过数据分析,对比快波偏振方向,证实微震识别获得的数据极大地增加了有效数据的数量,提高了结果的可靠性.研究结果表明,雅鲁藏布江缝合带与班公—怒江缝合带之间的拉萨地块东部地区,台站的快剪切波(快波)偏振方向主要受区域应力场影响,快波偏振方向主要是NS或NNE方向,表明了区域最大主压应力方向;但个别地震台站(当雄台)快波偏振方向受原地主压应力影响,其快波偏振方向既不平行于断裂走向也不平行于区域主压应力方向,揭示出地壳介质的局部变形导致的局部应力方向不同于青藏块体里的其他地区.研究区西部的改则、普兰和研究区北部的双湖,快波偏振方向显示与断裂等构造走向一致的特点.研究区东部的昌都和察隅,快波偏振方向除了与断裂走向(或构造线)一致,还与地表运动的方向相同,揭示了青藏块体东部的深部物质可能的运移方向.这个现象虽然还需更多的研究证实,但这个发现的重要启示是,地震各向异性结合地表变形可用于探讨地壳深部物质的运动.  相似文献   

四川雅安地区古冲积扇主量元素特征及其意义     

姜大伟  张世民 《第四纪研究》2020,(1):105-113

第四系是与人类生活关系密切的地层,山区地带的第四系主要由河流沉积物组成,这些沉积物的表面风化程度具有重要的环境意义。四川省雅安市地区发育了中更新统砾石层构成的古冲积扇名邛冲积扇和丹思冲积扇,现今废弃于岷江与青衣江之间,遭受了不同程度的侵蚀风化。对两个冲积扇不同位置采集样品,尝试利用主量元素分析冲积扇的风化程度。经过实验发现,主量元素分析可以很好地应用于第四系的测试,砾石间填充的基质砂能够合理反映沉积物经历的风化过程。实验结果表明,沉积物主量元素中长石矿物元素Ca、Na大量流失,而稳定矿物元素Si、Ti等偏高,说明冲积扇经历了长期的风化淋溶作用。A-CN-K图解体现出冲积扇经历了早期的斜长石风化,已经进入以钾长石和伊利石风化为标志的中期阶段。Pettijohn图解表明名邛冲积扇样品含有更多的石英砂岩,沉积物的成熟度较高。这些指标说明名邛冲积扇相比丹思冲积扇经历了更强的风化作用。结合冲积扇的年龄发现,风化速度随年龄的增长呈现减速的特征,体现了风化作用的阶段性.  相似文献   

利用远震研究四川盆地及其周缘瑞利面波相速度和方位各向异性          下载免费PDF全文

王小龙  雷兴林  马胜利  张烨  郭志  闻学泽 《地球物理学报》2020,63(2):445-459

基于四川盆地及周边的245个宽频带台站2010年9月—2014年9月期间的远震记录,提取双台路径瑞利面波相速度频散资料,反演得到四川盆地20～120s的高分辨率瑞利面波相速度及各向异性空间分布.在丰富区域地球物理基础数据的同时,结合已有研究成果对地壳上地幔变形耦合进行探讨,结果表明短周期(20～30s)的相速度分布与四川盆地的地质构造特征相吻合,作为川滇地块、松潘—甘孜地块和四川盆地之间的边界——龙门山断裂带和鲜水河断裂带对上述三个地块上地壳的速度结构具有明显的控制作用;松潘—甘孜地块,特别是川滇地块中下地壳普遍表现为明显的低速异常,表明中下地壳相对软弱;而四川盆地的中下地壳整体呈现相对高速,表明四川盆地具有相对坚硬的中下地壳.研究区域东南角接近北扬子地块与南扬子地块的缝合部位,呈现高速异常.四川盆地南部和东南邻区不同周期均具有较强的各向异性,且快波方向较为一致,反映这些地区不同深度变形耦合较好.四川盆地西部、北部及东北部邻区,不同周期的各向异性快波方向变化较大,不同深度变形耦合较差.这些特征与绕喜马拉雅东构造结的物质流动被扬子地块的高速地壳阻挡的宏观认识基本一致.  相似文献   

Stable carbon isotope signatures of cellulose in macrophytes collected from three eutrophic lakes in China     

《Limnologica》2020

Aquatic plants are essential for maintaining the diversity and stability of a lake ecosystem. Stable carbon isotopes (δ¹³C) of macrophytes have been widely used as a powerful tool to study ecological processes and paleoenvironmental evolution in lakes. Varying results are obtained when using the δ¹³C of macrophytes to study the changes in the lake environment at different spatio-temporal scales. Thus, sample preparation and subsequent laboratory analyses are crucial for studying environmental changes using the isotopic signal retained in the macrophytes, and are essential for the interpretation of isotope-environment relationships. This study analyzed the δ¹³C of different tissue components of macrophytes in three lakes of the lower Yangtze River basin, and a correlation analysis was performed on aquatic environments influencing the δ¹³C values in the different tissue components of macrophytes. The test results showed the difference between the δ¹³C values of the whole sample and cellulose. Relative analyses indicated that the major factors contributing to the δ¹³C variability in macrophytes were pH and the concentration of dissolved inorganic carbon (DIC). The δ¹³C of α-cellulose (δ¹³C_AC) is more sensitive to environmental variables than that of the whole sample (δ¹³C_W) and holocellulose (δ¹³C_HC). The results of this study imply that extraction of α-cellulose is a prerequisite for research on the changes in lake environment using δ¹³C of macrophytes. This study aims to provide theoretical and data basis for further research on the environmental and ecological change using stable carbon isotopes of aquatic plants.  相似文献   

Nishinoshima volcano in the Ogasawara Arc: New continent from the ocean?     

Yoshihiko Tamura  Osamu Ishizuka  Tomoki Sato  Alexander R. L. Nichols 《Island Arc》2019,28(1)

Nishinoshima, a submarine volcano in the Ogasawara Arc, approximately 1 000 km south of Tokyo, Japan, suddenly erupted in November 2013, after 40 years of dormancy. Olivine‐bearing phenocryst‐poor andesites found in older submarine lavas from the flanks of the volcano have been used to develop a model for the genesis of andesitic lavas from Nishinoshima. In this model, primary andesite magmas originate directly from the mantle as a result of shallow and hydrous melting of plagioclase peridotites. Thus, it only operates beneath Nishinoshima and submarine volcanoes in the Ogasawara Arc and other oceanic arcs, where the crust is thin. The primary magma compositions have changed from basalt, produced at considerable depth, to andesite, produced beneath the existing thinner crust at this location in the arc. This reflects the thermal and mechanical evolution of the mantle wedge and the overlying lithosphere. It is suggested that continental crust‐like andesitic magma builds up beneath submarine volcanoes on thin arc lithosphere today, and has built up beneath such volcanoes in the past. Andesites produced by this shallow and hydrous melting of the mantle could accumulate through collisions of plates to generate continental crust.  相似文献   

GEOCHEMISTRY     

《Abstract of Chinese Geological Literature》2014,(3)

正20141357 Guo Tao(School of Mathematics and Science,Shijiazhuang University of Economics,Shijiazhuang 050031,China);Hu Jiawen Assessment on the New Pressure-Volume-Temperature(PVT) Data of Supercritical Water(Geological Journal of China Universities,ISSN1006-7493,CN32-1440/P,19(3),2013,p.447-455,9 illus.,3 tables,32 refs.)Key words:supercritical fluids  相似文献   

关键金属元素分析测试技术方法应用进展   总被引：7，自引：5，他引：2  

李超  王登红  屈文俊  孟会明  周利敏  樊兴涛  李欣尉  赵鸿  温宏利  孙鹏程 《岩矿测试》2020,39(5):658-669

以稀有、稀散、稀土、铂族元素为主体的战略性关键金属矿产资源,在新材料、新能源和信息技术等新兴产业中发挥着越来越关键的作用。随着我国关键矿产资源地质调查的不断深入,关键金属元素以其赋存基体复杂、不同矿物含量差异大、化学性质不稳定等特点对分析测试技术提出了新的挑战。本文根据化学组成不同,对关键金属元素主要赋存基体进行了分类,主要分为硅酸盐、碳酸盐、硫酸盐、钨酸盐、磷酸盐、氧化物、硫化物、卤化物等。对于不同的基体岩石矿物,通常采用酸溶法(硝酸-氢氟酸组合、王水)或碱熔法等传统溶样方法进行化学消解。评述了当前关键金属元素测试常用的电子探针、电感耦合等离子体质谱、电感耦合等离子体发射光谱、X射线荧光光谱等仪器的特点及应用,总结了关键金属元素分析过程中出现的样品难溶解、回收率不完全、测试过程氧化物和同质异位素干扰、样品和标准基体不一致等常见问题,并提出了相应的解决方案。微区原位分析凭借其高效率、低成本、高空间分辨率的优势,以及野外现场分析凭借其简单快速、贴近野外工作的特点是关键金属元素测试技术发展的主要趋势。  相似文献   

苔藓生物结皮层腐殖质组成变化特征研究          下载免费PDF全文

闫德仁  张胜男  吴振廷 《干旱区地理》2019,42(6):1354-1358

腐殖质组成是表征土壤化学性质的主要指标之一，在某种程度对评价风沙土的发育过程具有意义。采集了不同气候区沙地沙漠苔藓生物结皮层样品，采用重铬酸钾容量法和光密度法测定了苔藓结皮层腐殖质组成含量和胡敏酸吸光特性。结果表明：随着干燥指数的增加，苔藓结皮层有机质含量由14.93 g·kg^-1降低到9.89 g·kg^-1，腐殖酸总量由5.1 g·kg^-1降低到2.0 g·kg^-1，胡敏酸含量由2.9 g·kg^-1降低到 0.7 g·kg^-1，富里酸含量由2.2 g·kg^-1降低到1.3 g·kg^-1，胡敏酸与富里酸比值（HA/FA）由1.32降低到0.54，E₄/E₆比值则由4.28增加到5.83。苔藓结皮层腐殖质组成含量及胡敏酸吸光特性具有地带性变化趋势，并影响着生物结皮层及流动风沙土的发育演变过程。  相似文献