YSI(多参数水质检测仪)测定叶绿素a浓度的准确性及误差探讨

YSI(多参数水质检测仪)由于其快速、轻便的特点,已广泛应用于野外水体中叶绿素a的测定.通过将YSI测得的叶绿素a值与分光光度法测定值进行比较,对YSI6600水质测定的准确性和数据采集进行评估.结果显示,YSI测定值多数偏低,且与分光光度法测定值之间存在显著性差异;时间上,冬季比夏季具有更大的线性相关性.分段回归结果显示,随着叶绿素a浓度不断增大,两组数据的差值也不断增大.YSI测定误差产生于3个方面:(1)测定前YSI校准方法的不同;(2)其它种类具有荧光特性色素的存在;(3)YSI自身结构.     

内蒙古测震台网台站布局对地震定位的影响

选取2009年1月至2016年5月内蒙古中西部及邻区55次M ≥ 3.0地震,通过调整台站空隙角、近台距离、远台距离、定位台站数,改变并对比定位子台网布局对地震定位精度的影响,进而研究定位子台网的选取规则。分区域探讨2种台站分布模式下地震的定位偏差、水平误差、拟合残差随空隙角、近台距离、远台距离、台站分布均匀度的变化及水平误差和定位偏差与拟合残差的关系。分析发现,地震速报选取9-12个台站,且台站分布相对合理的定位子台网参与定位,结果较好,使用水平误差评估定位效果更准确。     

辽宁测震台网地震观测报告质量分析

就地震分布、震相质量、深度分布以及地震震级等,对辽宁测震台网2010-2017年地震观测报告进行分析,得到辽宁地区地震波主要震相的平均传播速度,分别为：Pn震相平均传播速度为7.87 km/s,Pg震相平均传播速度为4.48 km/s,Sn震相平均传播速度为4.48 km/s,Sg震相平均传播速度为3.56 km/s,认为引起震相走时偏差较大的主要原因为地震定位误差及震相不易识别。     

Raingauge network optimization in a tropical urban area by coupling cross-validation with the geostatistical technique

An adequate and reliable raingauge network is essential for observing rainfall data in hydrology and water resource applications. A raingauge network developed for a catchment area is commonly extended periodically to increase data accuracy. Due to financial constraints, the network is reviewed for the optimal number of stations. A new optimization approach is developed in this study by coupling a cross-validation technique with a geostatistical method for raingauge network optimization to prioritize raingauge stations. The spatial interpolation error of the spatial rainfall distribution, measured as the root mean square error (E_rms) optimization criterion is applied to a raingauge network in a tropical urban area. The results indicate that this method can successfully optimize the number of rainfall stations in an existing raingauge network, as the stations are prioritized based on their importance in the network.     

基于洪水预报系统误差反演的多河段联合校正方法

提出一种基于洪水预报误差系统反演的多河段联合校正方法.采用马斯京根法矩阵方程描述多河段多区间入流的河道汇流过程,基于动力系统反演理论建立洪水预报误差的递推方程,最后利用修正后的多河段状态变量经演算得到预报断面的洪水过程,进而达到多河段联合校正目的.对大渡河上游的应用示例结果表明：多河段联合校正方法考虑了河系中断面间的水力联系及预报误差在时程上的传递规律,可充分利用上游多断面实测和校正信息进行下游预报断面的误差修正,因此具有更高的校正精度和稳定性.     

Archival photogrammetric analysis of river–floodplain systems using Structure from Motion (SfM) methods

In this study we evaluate the extent to which accurate topographic data can be obtained by applying Structure from Motion (SfM) photogrammetric methods to archival imagery. While SfM has proven valuable in photogrammetric applications using specially acquired imagery (e.g. from unmanned aerial vehicles), it also has the potential to improve the precision of topographic data and the ease with which can be produced from historical imagery. We evaluate the application of SfM to a relatively extreme case, one of low relative relief: a braided river–floodplain system. We compared the bundle adjustments of SfM and classical photogrammetric methods, applied to eight dates. The SfM approach resulted in data quality similar to the classical approach, although the lens parameter values (e.g. focal length) recovered in the SfM process were not necessarily the same as their calibrated equivalents. Analysis showed that image texture and image overlap/configuration were critical drivers in the tie‐point generation which impacted bundle adjustment quality. Working with archival imagery also illustrated the general need for the thorough understanding and careful application of (commercial) SfM software packages. As with classical methods, the propagation of (random) error in the estimation of lens and exterior orientation parameters using SfM methods may lead to inherent systematic error in the derived point clouds. We have shown that linear errors may be accounted for by point cloud registration based on a reference dataset, which is vital for the further application in quantitative morphological analyses when using archival imagery. Copyright © 2016 John Wiley & Sons, Ltd.     

Event and model dependent rainfall adjustments to improve discharge predictions

Most conceptual rainfall–runoff models use as input spatially averaged rainfall fields which are typically associated with significant errors that affect the model outcome. In this study, it was hypothesised that a simple spatially and temporally averaged event-dependent rainfall multiplier can account for errors in the rainfall input. The potentials and limitations of this lumped multiplier approach were explored by evaluating the effects of multipliers on the accuracy and precision of the predictive distributions. Parameter sets found to be behavioural across a range of different flood events were assumed to be a good representation of the catchment dynamics and were used to identify rainfall multipliers for each of the individual events. An effect of the parameter sets on identified multipliers was found; however, it was small compared to the differences between events. Accounting for event-dependent multipliers improved the reliability of the predictions. At the cost of a small decrease in precision, the distribution of identified multipliers for past events can be used to account for possible rainfall errors when predicting future events. By using behavioural parameter sets to identify rainfall multipliers, the method offers a simple and computationally efficient way to address rainfall errors in hydrological modelling.     

一种卫星钟差精度评估方法

GNSS观测量测量的是测站与卫星间的相对时间延迟,卫星钟差求解的是相对于基准钟的相对钟差,因此卫星钟差的精度评估方法不同于其他GNSS产品。分析了卫星钟差的精度评估方法,采用消除卫星钟系统偏差的方法进行钟差精度的评估,得到的各产品的精度评定结果与各产品公布的钟差精度基本一致,证明了此方法的有效性。     

通量管积分瑞利-泰勒不稳定性的半球不对称和随经度变化的研究

本文利用通量管积分方法,对磁南北半球分别沿磁力线积分,研究背景电离层南-北半球不对称以及中性风场和磁偏角随经度的变化对广义瑞利-泰勒不稳定性和电离层不规则结构生成和发展的影响.结果表明,通量管积分广义瑞利-泰勒不稳定性线性增长率存在显著的半球不对称,南北半球不对称的中性风场是导致电离层不规则结构呈南北分布不对称的重要因素;随经度变化的中性风场和磁偏角对瑞利-泰勒不稳定性的经度变化有重要影响,它们可能是导致不规则结构出现率经度变化的主要控制因素.     

An optimized use of limited ground based topographic data for river applications

A prime requirement for hydrological applications,such as sediment budgeting or numerical modelling,is that produced Digital Terrain Models(DTMs)accurately represent the shape of landforms,especially for river reaches where data are not homogeneous.DTM error is a function of data point measurement accuracy and density and also of the field survey strategy when limited amounts of data will be acquired.This paper aims to advance the importance of the field survey strategy for the specific,but common cases,where only limited topographic data will be available.This methodology is based on the idea that any feature can be properly described by a set of cross sections and breaklines describing both main and secondary directions of the flow.Then,a longitudinal linear interpolation can be applied to the defined homogeneous zones.This morphologically oriented(MO)method that includes data acquisition strategy and interpolation,was validated using a reference DTM derived from LiDAR measurements.An estimation of the uncertainties also is suggested based on the distance of the nearest point and the local slope using a geographically weighted regression.The proposed MO method is typically applicable to Alpine river reaches characterized by multiple channels that may always be underwater and not navigable such as an alternate bar system with secondary and transverse channels.