Impacts of uncertain river flow data on rainfall‐runoff model calibration and discharge predictions

In order to quantify total error affecting hydrological models and predictions, we must explicitly recognize errors in input data, model structure, model parameters and validation data. This paper tackles the last of these: errors in discharge measurements used to calibrate a rainfall‐runoff model, caused by stage–discharge rating‐curve uncertainty. This uncertainty may be due to several combined sources, including errors in stage and velocity measurements during individual gaugings, assumptions regarding a particular form of stage–discharge relationship, extrapolation of the stage–discharge relationship beyond the maximum gauging, and cross‐section change due to vegetation growth and/or bed movement. A methodology is presented to systematically assess and quantify the uncertainty in discharge measurements due to all of these sources. For a given stage measurement, a complete PDF of true discharge is estimated. Consequently, new model calibration techniques can be introduced to explicitly account for the discharge error distribution. The method is demonstrated for a gravel‐bed river in New Zealand, where all the above uncertainty sources can be identified, including significant uncertainty in cross‐section form due to scour and re‐deposition of sediment. Results show that rigorous consideration of uncertainty in flow data results in significant improvement of the model's ability to predict the observed flow. Copyright © 2010 John Wiley & Sons, Ltd.     

Lithospheric Electrical Structure across the Eastern Segment of the Altyn Tagh Fault on the Northern Margin of the Tibetan Plateau

Project INDEPTH (InterNational DEep Profiling of Tibet and the Himalaya) is an interdisciplinary program designed to develop a better understanding of deep structures and mechanics of the Tibetan Plateau. As a component of magnetotelluric (MT) work in the 4th phase of the project, MT data were collected along a profile that crosses the eastern segment of the Altyn Tagh fault on the northern margin of the plateau. Time series data processing used robust algorithms to give high quality responses. Dimensionality analysis showed that 2D approach is only valid for the northern section of the profile. Consequently, 2D inversions were only conducted for the northern section, and 3D inversions were conducted on MT data from the whole profile. From the 2D inversion model, the eastern segment of the Altyn Tagh fault only appears as a crustal structure, which suggests accommodation of strike slip motion along the Altyn Tagh fault by thrusting within the Qilian block. A large-scale off-profile conductor within the mid-lower crust of the Qilian block was revealed from the 3D inversion model, which is probably correlated with the North Qaidam thrust belt. Furthermore, the unconnected conductors from the 3D inversion model indicate that deformations in the study area are generally localized.     

基于图像测量的花键套端面尺寸检测

设计了一套基于图像测量技术的花键套端面尺寸检测系统,采用高分辨率工业相机获取零件图像信息,使用相机标定技术标定相机参数,以校正光学系统导致的零件图像畸变,通过图像处理技术处理并分析图像,得到图像特征尺寸信息,最后采用分区域标定像素当量的方法得到零件实际尺寸.使用该检测系统与三坐标测量仪检测系统进行对比实验,实验结果显示,该系统尺寸检测结果与三坐标测量仪检测结果比照相差不超过10 μm.每个零件检测时间不超过20 s,速度远远快于平均检测时间需约2 min的三坐标测量仪检测方法,因此在满足检测精度的基础上大大提高了检测速度,实现了花键套尺寸批量检测.     

Distribution of CMEs with Different Angular Widths and Comparison with the Phase of Sunspot Number in the 23rd Solar Cycle

The variation of the number of coronal mass ejections (CMEs) with different angular widths in the period of 1996-2008 is analyzed statistically in this paper, together with a comparison of the feature of time variation between the number of CMEs with some typical angular widths and the number of sunspots.     

Lateglacial landform associations at Jæren (SW Norway) and their glaci-dynamic implications

The Jæren lowland is located on the southwestern coast of Norway between a mountainous region in the east and the offshore Norwegian Channel in the west. During the Last Glacial Maximum, Jæren was in an intermediate position between an ice stream following the Norwegian Channel northwards, and westward flowing inland ice. The dynamic behaviour of the inland ice and the interaction with the ice stream are examined by means of geomorphological analysis of digital terrain models and sedimentological investigations. SW-trending drumlins were formed at Jæren below tributary ice from the inland, feeding into the Norwegian Channel Ice Stream. The presence of Rogen moraine in the central part of Jæren indicates a frozen substratum prior to their formation, and this suggests a transition to cold-based ice between the tributaries. The deglaciation of the Norwegian Channel at about 15 ka BP resulted in an unstable ice front for the inland ice sheet. The formation of Rogen moraine may be explained by a dynamic advance resulting in extensional flow and fracturing of the frozen substratum between the tributaries. The dynamic advance was followed by an early deglaciation of the coastal areas as evidenced by shallow marine sediments. Deformation of the shallow marine sand indicates a glacial readvance through the valleys formerly acting as tributaries to the ice stream.     

Orbital-scale record of the late Cenomanian–Turonian oceanic anoxic event (OAE-2) in the Tarfaya Basin (Morocco)

High sedimentation rates (up to 12 cm/kyear) of laminated organic carbon-rich biogenic limestones in the Tarfaya Basin provide an unusually high (millennial) resolution record of the late Cenomanian oceanic anoxic event (OAE-2). The global positive carbon-isotope excursion across the Cenomanian–Turonian corresponds to 11 light/dark sedimentary cycles. We interpret these cycles as a response to orbital obliquity variation and estimate the duration of the complete excursion as 440 kyear or one long eccentricity cycle. On this timescale, the main increase in ¹³C values occurred over a short time interval of less than 20 kyear in the late Cenomanian and reached a first maximum approximately 15 kyear prior to the bulk (mainly coccoliths) ¹⁸O-derived sea surface maximum temperature that occurs coeval to the extinction of Rotalipora cushmani. Organic carbon-accumulation rates follow obliquity cycles, reaching a maximum approximately 10 kyear after the last occurrence of R. cushmani, then slowly decreasing during the early Turonian. Thus, the maximum temperature and the maximum organic carbon accumulation in the Tarfaya Basin lagged by at least 15 kyear behind the global carbon-isotope shift and a proposed reduction of atmospheric CO₂ content. The climate change across the Cenomanian/Turonian boundary probably occurred independent of CO₂ levels and may have been controlled by different greenhouse gases (water vapour and methane) and changes in ocean circulation (i.e., opening of the Equatorial Atlantic gateway)