Hydrological characteristics of vegetated river flows: a laboratory flume study     

John Z. Shi  Yan-Hong Li  Jocelyne M.R. Hughes  Ming Zhao 《水文科学杂志》2013,58(5):1047-1058

Abstract

Laboratory flume experiments were undertaken to measure the vertical profiles of mean flow velocity for three different flow discharges and four different stem densities of Hydrilla verticillata. The data were used to calculate three parameters, namely Manning's roughness coefficient, the Reynolds number and the Froude number. In addition, empirical equations were obtained for the vertical distribution of measured flow velocity within the transitional zone and above the plant canopy. The results show that: (a) the vertical distribution of measured flow velocity exhibits three zone profiles; (b) Manning's roughness coefficient decreases with increasing depth-averaged flow velocity; (c) the relationship between Manning's roughness coefficient and the depth-averaged flow velocity is within the smooth left inverse curve; (d) Manning's roughness coefficient significantly changes with increasing density of Hydrilla; (e) the Froude number is independent of the density of Hydrilla; and (f) both the Reynolds number and the Froude number increase with increasing depth-averaged flow velocity.

Citation Shi, J.Z., Li, Y.-H., Hughes, J.M.R., and Zhao, M., 2013. Hydrological characteristics of vegetated river flows: a laboratory flume study. Hydrological Sciences Journal, 58 (5), 1047–1058.

Editor Z.W. Kundzewicz  相似文献   

2010年新西兰M_W7.0主震与2011年M_W6.1余震近场强地面运动特征比较分析     

孟令媛  史保平  刘杰 《地震学报》2013,35(3):351-368

2010年9月3日16时35分46秒新西兰南岛Greendale附近发生了M_W7.0地震, 震源深度约10.0 km. 2011年2月21日新西兰南岛又发生了M_W6.1地震, 为2010年M_W7.0主震后最大的一次余震, 震源深度约5.0 km, 发震断层为Christchurch南约9 km一条近东西走向逆冲的隐伏断层, 该地震造成Christchurch城内多处建筑物严重损毁. 本文分析了2010年新西兰地震事件M_W7.0主震与M_W6.1余震强地面运动的特征. 新西兰M_W6.1余震近场强地面运动整体高于M_W7.0主震. 将主震和余震的强震观测记录分别与新一代衰减关系(NGA)进行对比, 发现余震强震观测数据整体高于其震级对应的NGA. 分别选取距离主震和余震震中最近且强震观测记录最高的两个台站(GDLC台站和HVSC台站)作为参照台站, 建立动态复合震源模型(DCSM)及有限断层随机振动模型(SFFM)进行强地面运动的模拟计算, 分析两种模型的模拟结果并对比二者的优势及局限, 以便在未来工作中更好地通过模型计算强地面运动特征, 实现区域化特征快速、 实时分析及局部重点、 细致分析相结合的目标.   相似文献   

Partitioning of Fluoroquinolones on Wastewater Sludge     

Xuefei Zhou  Yalei Zhang  Lu Shi  Jiabin Chen  Zhimin Qiang  Tian C. Zhang 《洁净——土壤、空气、水》2013,41(8):820-827

Laboratory‐scale batch experiments were conducted to investigate the adsorption behavior of eight fluoroquinolones (FQs) on aerobic, anoxic, and anaerobic sludge, under different adsorpiton time, pH, and temperature conditions. Results indicated that adsorption of FQs onto all sludge was a physical sorption process. The relationship of the partitioning coefficient (K_d) and the octanol/water partition coefficient (K_ow) for each FQ was established. The adsorbed fraction of FQs on sludge could then be predicted with the K_d. It was calculated that about 50–72% of the FQs were adsorbed on the sludge. Therefore, the adsorption effect must be considered when studying the fate and occurrence of FQs in wastewater treatment systems.  相似文献   

Development of a data mining method for land control     

Wang Shuliang  Wang Xinzhou  Shi Wenzhong 《地球空间信息科学学报》2013,16(1):68-76

Land resources are facing crises of being misused, especially for an intersection area between town and country, and land control has to be enforced. This paper presents a development of data mining method for land control. A vector-match method for the prerequisite of data mining i. e., data cleaning is proposed, which deals with both character and numeric data via vectorizing character-string and matching number. A minimal decision algorithm of rough set is used to discover the knowledge hidden in the data warehouse. In order to monitor land use dynamically and accurately, it is suggested to set up a real-time land control system based on GPS, digital photogrammetry and online data mining. Finally, the means is applied in the intersection area between town and country of Wuhan city, and a set of knowledge about land control is discovered.  相似文献   

QTPV data model and algorithm and its application to geological exploration engineering     

Cheng Penggen  Shi Wenzhong  Gong Jianya  Zhou Guoqing 《地球空间信息科学学报》2013,16(1):64-71

3D spatial data model and simulating are the core of 3D GIS can be adopted in different domains. A data model based on Quasi Tri-Prism Volume (QTPV) has been proposed. QTPV definition and its special cases have been discussed. Using QTPV and its special cases, irregular natural geological bodies and regular subsurface engineering can be described efficiently. The proposed model is composed of five primitives and six objects. Data structures and topological relationship of the fives primitives and three objects describing stratigraphy are designed in detail. Some schemes are designed for the QTPV modelling of stratigraphy and subsurface engineering according to modelling data. The model manipulation method of QTPV cutting by an arbitrary plane is discussed. Using VC++ 6.0 programming language integrated with SQL database and OpenGL graphic library under windows environment, a system prototype 3DGeoMV has been developed. The experiment result shows that the QTPV model is feasible and efficient in modelling subsurface engineering.  相似文献   

Development of a GIS data model with spatial,temporal and attribute components based on object-oriented approach     

Shi Wenzhong  Zhang Minwen 《地球空间信息科学学报》2013,16(1):17-23

This paper presents a conceptual data model, the STA-model, for handling spatial, temporal and attribute aspects of objects in GIS. The model is developed on the basis of object-oriented modeling approach. This model includes two major parts: (a) modeling the signal objects by STA-object elements, and (b) modeling relationships between STA-objects. As an example, the STA-model is applied for modeling land cover change data with spatial, temporal and attribute components.  相似文献   

Box-Cox正态转换在长江子流域极端降水气候事件判定中的应用     

吴瑶  杜良敏  刘长征  张俊 《湖北气象》2022,41(1):94-100

利用1961-2017年长江流域700个气象站点逐月降水资料计算长江流域9个子流域面雨量,采用基于Box-Cox正态分布转换后的百分位法对长江流域不同时间长度的极端降水气候事件阈值进行界定。结果表明,在数据序列长度发生变化的情况下,面雨量序列经Box-Cox正态转换后,计算得到的极端降水气候事件阈值的变化相较于常规百分位法明显减小,具有更为稳健的特性,从而使得相应极端降水气候事件个例的挑选更为稳定。根据该方法得到的阈值,对2018年汛期(6-8月)长江各子流域极端降水气候事件进行判定,岷沱江流域发生了极端多雨气候事件,而长江干流重庆-宜昌段、汉江及中游干流区间发生了极端少雨气候事件。  相似文献   

Interannual variability of the sea surface salinity and its related freshwater flux in the tropical Pacific: A comparison of CMIP5 and CMIP6          下载免费PDF全文

Hai Zhi  Yu Huang  Pengfei Lin  Shiwei Shi  Meng Dong 《大气和海洋科学快报》2022,15(4):100190

This paper assesses the interannual variabilities of simulated sea surface salinity (SSS) and freshwater flux (FWF) in the tropical Pacific from phases 5 and 6 of the Coupled Model Intercomparison Project (CMIP5 and CMIP6). The authors focus on comparing the simulated SSS and FWF responses to El Niño–Southern Oscillation (ENSO) from two generations of models developed by the same group. The results show that CMIP5 and CMIP6 models can perform well in simulating the spatial distributions of the SSS and FWF responses associated with ENSO, as well as their relationship. It is found that most CMIP6 models have improved in simulating the geographical distribution of the SSS and FWF interannual variability in the tropical Pacific compared to CMIP5 models. In particular, CMIP6 models have corrected the underestimation of the spatial relationship of the FWF and SSS variability with ENSO in the central-western Pacific. In addition, CMIP6 models outperform CMIP5 models in simulating the FWF interannual variability (spatial distribution and intensity) in the tropical Pacific. However, as a whole, CMIP6 models do not show improved skill scores for SSS interannual variability, which is due to their overestimation of the intensity in some models. Large uncertainties exist in simulating the interannual variability of SSS among CMIP5 and CMIP6 models and some improvements with respect to physical processes are needed.摘要通过比较CMIP5和CMIP6来自同一个单位两代模式模拟, 表明CMIP5和CMIP6均能较好地模拟出热带太平洋的海表盐度 (SSS) 和淡水通量 (FWF) 对ENSO响应的分布及其响应间的关系. 与CMIP5模式相比, 大部份CMIP6模式模拟的SSS和FWF年际变化分布均呈现改进, 特别是纠正了较低的中西太平洋SSS和FWF变化的空间关系. 但是, 整体上, CMIP6模式模拟的SSS年际变化技巧没有提高, 与SSS年际变率的强度被高估有关. CMIP5和CMIP6模式模拟SSS的年际变化还存在较大的不确定性, 在物理方面需要改进.  相似文献   

Tropical forcing of Australian extreme low minimum temperatures in September 2019     

Lim  Eun-Pa  Hendon  Harry H.  Shi  Li  de Burgh-Day  Catherine  Hudson  Debra  King  Andrew  Trewin  Blair  Griffiths  Morwenna  Marshall  Andrew 《Climate Dynamics》2021,56(11):3625-3641

We explore the causes and predictability of extreme low minimum temperatures (T_min) that occurred across northern and eastern Australia in September 2019. Historically, reduced T_min is related to the occurrence of a positive Indian Ocean Dipole (IOD) and central Pacific El Niño. Positive IOD events tend to locate an anomalous anticyclone over the Great Australian Bight, therefore inducing cold advection across eastern Australia. Positive IOD and central Pacific El Niño also reduce cloud cover over northern and eastern Australia, thus enhancing radiative cooling at night-time. During September 2019, the IOD and central Pacific El Niño were strongly positive, and so the observed T_min anomalies are well reconstructed based on their historical relationships with the IOD and central Pacific El Niño. This implies that September 2019 T_min anomalies should have been predictable at least 1–2 months in advance. However, even at zero lead time the Bureau of Metereorolgy ACCESS-S1 seasonal prediction model failed to predict the anomalous anticyclone in the Bight and the cold anomalies in the east. Analysis of hindcasts for 1990–2012 indicates that the model's teleconnections from the IOD are systematically weaker than the observed, which likely stems from mean state biases in sea surface temperature and rainfall in the tropical Indian and western Pacific Oceans. Together with this weak IOD teleconnection, forecasts for earlier-than-observed onset of the negative Southern Annular Mode following the strong polar stratospheric warming that occurred in late August 2019 may have contributed to the T_min forecast bust over Australia for September 2019.

  相似文献   

DETERMINING GROUNDWATER SUSTAINABLE YIELD IN BASINS:A CASE STUDY OF YINMA RIVER BASIN     

Shi Fengzhi  Chi Baoming  Zhao Chengyi  Lan Shuangshuang 《第四纪研究》2012,32(2)

地下水可持续开采量的确定与评价既是合理开发地下水资源的基础,又是水文地质学研究中的难点.为克服没有统一的评价标准以及对众多约束条件难以定量化计算的难点,本文从提高流域内整体水资源的利用率出发,综合考虑了流域水资源整体开发利用效益和生态环境需水,以及人工调蓄作用对地下水系统的影响作用,提出了流域地下水可持续开采量的概念;论述了所提出概念的内涵;建立了由流域水循环模拟模型、水资源开发综合效益模型和可持续开采量优化模型组成的流域地下水可持续开采量的评价体系,将流域水循环模拟模型作为研究平台,以水资源开发的综合效益模型作为选优依据,以不同生态环境需水条件为约束条件,对施加其上的各种不同调控措施进行模拟,最后通过性价比的综合分析与评估,得到可持续开发方案下的流域地下水可持续开采量.以吉林省饮马河流域为例展开实例应用,确定饮马河流域最满意的开发模式下,即水库高比例供水(水库供水4.850×108m3),保证河道适宜生态需水时,饮马河流域地下水可持续开采量为2.516×108m3/a.  相似文献