CMIP5模式对东太平洋ITCZ偶极子模态模拟能力的评估

本研究利用第五次国际间耦合模式比较计划(Coupled Model Intercomparison Project phase 5, CMIP5)中的24个模式的工业革命前控制试验(Pre-industrial Control, picontrol)模拟结果, 结合观测资料, 评估了24个CMIP5 模式对东太平洋热带辐合带偶极子(Eastern Pacific ITCZ dipole, EPID)降水模态的模拟能力, 并建立了其与模式对热带太平洋气候态模拟之间的联系。结果表明: 1) 绝大多数模式在北半球春季(2—4月)对EPID模态模拟能力较差, 主要原因在于CMIP5模式对热带辐合带(Intertropical Convergence Zone, ITCZ)的模拟偏差, 其中模拟效果较差的模式在2—4月的气候态降水分布在赤道以南, 且降水普遍偏强; 2) 对各模式的EPID模态选取的季节按照技巧评分最高进行调整后, 大部分模式能较好地模拟出EPID模态的空间分布特点, 技巧评分在0.6以上, 其中模拟效果好的模式(技巧评分大于0.7)中EPID模态出现的月份同时在中东太平洋气候态表现出“双ITCZ”特征, 且多模式集合结果的模拟误差小于绝大多数模式。     

遥感蚀变信息检测中背景与干扰问题研究

在不同自然景观区的遥感蚀变信息检测中,背景与干扰是2个复杂而又容易混淆的研究对象。本文结合光谱混合模型理论与随机变量概率分布相关理论,深入分析了遥感数据的光谱空间几何结构特征(重点剖析二维散点图),系统研究了背景与干扰的关系、复杂度以及干扰地物类型的划分等问题。这些问题的探讨为遥感蚀变信息检测的最佳方案设计和蚀变信息潜在性评价与准确提取提供了技术思路。     

Exploring the sensitivity of coastal inundation modelling to DEM vertical error

As sea level is projected to rise throughout the twenty-first century due to climate change, there is a need to ensure that sea level rise (SLR) models accurately and defensibly represent future flood inundation levels to allow for effective coastal zone management. Digital elevation models (DEMs) are integral to SLR modelling, but are subject to error, including in their vertical resolution. Error in DEMs leads to uncertainty in the output of SLR inundation models, which if not considered, may result in poor coastal management decisions. However, DEM error is not usually described in detail by DEM suppliers; commonly only the RMSE is reported. This research explores the impact of stated vertical error in delineating zones of inundation in two locations along the Devon, United Kingdom, coastline (Exe and Otter Estuaries). We explore the consequences of needing to make assumptions about the distribution of error in the absence of detailed error data using a 1 m, publically available composite DEM with a maximum RMSE of 0.15 m, typical of recent LiDAR-derived DEMs. We compare uncertainty using two methods (i) the NOAA inundation uncertainty mapping method which assumes a normal distribution of error and (ii) a hydrologically correct bathtub method where the DEM is uniformly perturbed between the upper and lower bounds of a 95% linear error in 500 Monte Carlo Simulations (HBM+MCS). The NOAA method produced a broader zone of uncertainty (an increase of 134.9% on the HBM+MCS method), which is particularly evident in the flatter topography of the upper estuaries. The HBM+MCS method generates a narrower band of uncertainty for these flatter areas, but very similar extents where shorelines are steeper. The differences in inundation extents produced by the methods relate to a number of underpinning assumptions, and particularly, how the stated RMSE is interpreted and used to represent error in a practical sense. Unlike the NOAA method, the HBM+MCS model is computationally intensive, depending on the areas under consideration and the number of iterations. We therefore used the HBM+ MCS method to derive a regression relationship between elevation and inundation probability for the Exe Estuary. We then apply this to the adjacent Otter Estuary and show that it can defensibly reproduce zones of inundation uncertainty, avoiding the computationally intensive step of the HBM+MCS. The equation-derived zone of uncertainty was 112.1% larger than the HBM+MCS method, compared to the NOAA method which produced an uncertain area 423.9% larger. Each approach has advantages and disadvantages and requires value judgements to be made. Their use underscores the need for transparency in assumptions and communications of outputs. We urge DEM publishers to move beyond provision of a generalised RMSE and provide more detailed estimates of spatial error and complete metadata, including locations of ground control points and associated land cover.     

地中电偶极源极低频电磁场的分布与传播特征

利用层状大地中偶极源响应的正演算法, 计算地中电偶极源激发的极低频地震电磁场并分析其在地球环境下的传播特征.设计了多个水平层状地球模型, 分别模拟和展示了深埋地中的电偶极源的响应和空间分布特征.重点分析了含地壳波导+LAI波导模型的高阻大地中, 倾斜电偶极源激励响应随观测点的偏移距和垂直位置、激励源深度、地壳波导结构和参数变化时各场量响应的幅频特征.研究表明, 用倾斜电偶极源模拟和分析高阻大地中孕震电磁辐射的响应及在大地电磁系统中的传播特性是可行的; 模拟的高阻大地中的电磁辐射在地壳波导和LAI波导中均表现有慢衰减或幅值增强特性, 但两个波导效应具有不同的频率选择性; 高阻大地中的电磁辐射在波导的高阻介质中具有幅值强、衰减慢的特点.建议在高阻地层出露的地表、井中或海底的高阻岩层中以及大气层中布设测站.

     

利用爆破事件分析不同速度模型下常规定位方法定位结果

地震定位对速度模型的依赖性很强。四川地区地形复杂,常规工作中可选取多种速度模型进行定位。川西龙门山断裂带为东南部四川盆地和西北部青藏高原东部山区的明显分界线,近年在此断裂带上发生多次较大地震。对发生在该断裂带附近的6个爆破事件和15个天然地震重新定位,并对比结果。研究表明,相同台站包围情况下,川滇3D速度模型稳定性最好,但对浅表爆破不太准确。相比HypoSat(一维速度模型)组合,台站分布对Hypo2000(一维速度模型)和Hypo2000(赵珠速度模型)组合的定位结果影响较大。     

船舶转向避让碰撞距离模型的确定

船舶碰撞距离直接影响船舶碰撞危险度的大小。分析了影响船舶碰撞距离的因素:会遇 态势、船舶的操纵性能、船舶尺度、船舶速度等;给出目标船静止不动时和目标船有运动速度时的 船舶转向避让时碰撞距离数学模型,为研究船舶碰撞危险度和船舶自动避碰决策系统提供理论依 据。     

两种电离层延迟改正模型对星载单频GPS实时定轨精度的影响

采用单频星载GPS实测伪距和载波相位观测值,结合不同的电离层延迟改正模型进行模拟实时定轨实验,分析单频实时定轨的精度。不同轨道高度的低轨卫星实验结果表明,在卫星轨道较高(500 km以上)时,使用单频伪距观测值与改进的Klobuchar模型,实时定轨位置精度可达0.86 m(三维RMS),速度精度可达0.9 mm/s,接近甚至优于双频伪距实时定轨的轨道精度;使用单频码相无电离层组合观测值时,实时定轨位置精度可达0.54 m,速度精度可达0.55 mm/s。采用合适的电离层延迟改正模型,廉价的单频星载接收机可应用于微小卫星的实时定轨。     

大别山及其周边现今垂直形变研究

基于1980年、2005年和2015年3期区域精密水准网观测资料,利用线性动态平差模型计算获取大别山地区水准网长期垂直运动速度场图像。研究发现,淮河平原地表下沉较为严重,大别山呈现弱隆升趋势运动,长江谷地边缘地区较大别山区呈现明显的隆升运动。跨郯庐断裂带水准剖面结果显示,垂直运动与地形呈负相关和弱相关。     

On the multivariate total least-squares approach to empirical coordinate transformations. Three algorithms

The multivariate total least-squares (MTLS) approach aims at estimating a matrix of parameters, Ξ, from a linear model (Y−E _Y = (X−E _X ) · Ξ) that includes an observation matrix, Y, another observation matrix, X, and matrices of randomly distributed errors, E _Y and E _X . Two special cases of the MTLS approach include the standard multivariate least-squares approach where only the observation matrix, Y, is perturbed by random errors and, on the other hand, the data least-squares approach where only the coefficient matrix X is affected by random errors. In a previous contribution, the authors derived an iterative algorithm to solve the MTLS problem by using the nonlinear Euler–Lagrange conditions. In this contribution, new lemmas are developed to analyze the iterative algorithm, modify it, and compare it with a new ‘closed form’ solution that is based on the singular-value decomposition. For an application, the total least-squares approach is used to estimate the affine transformation parameters that convert cadastral data from the old to the new Israeli datum. Technical aspects of this approach, such as scaling the data and fixing the columns in the coefficient matrix are investigated. This case study illuminates the issue of “symmetry” in the treatment of two sets of coordinates for identical point fields, a topic that had already been emphasized by Teunissen (1989, Festschrift to Torben Krarup, Geodetic Institute Bull no. 58, Copenhagen, Denmark, pp 335–342). The differences between the standard least-squares and the TLS approach are analyzed in terms of the estimated variance component and a first-order approximation of the dispersion matrix of the estimated parameters.     

柴达木盆地东部石炭系页岩三维裂缝网络模型研究

裂缝既是页岩气的聚集空间,同时也是页岩气的运移通道, 对页岩气成藏起着重要控制作用。裂缝的产状、密度、组合特征等很大程度上决定了页岩气是否具有开发价值。该研究对柴达木盆地东部的13个露头的岩石裂缝进行了野外观测统计,实测裂缝1 000多条,选取了三个具有代表性的页岩露头进行统计分析建模。通过野外观测和室内统计分析发现,工作区页岩裂缝发育有三组(某些地段一组不发育),各组裂缝的方向满足Fisher分布,迹线长度满足对数正态分布。确定了各组裂缝方向、长度的均值和方差,以及各组裂缝的密度,建立了三维裂缝网络模型,绘出了模拟的三维裂缝网络图。裂缝三维模型为圆盘模型,即假设单个裂缝三维空间上具有圆盘形状。建模过程采用了逆建模方法,其基本原则是通过拟合实测的二维露头观测数据,优化裂缝三维大小和密度参数,使模型能够准确再现野外所观测到的实际现象,包括露头面上不同裂缝的数量、密度和长度。该研究对柴达木盆地东部石炭系页岩裂缝描述达到了定量化,为研究页岩中油气运移提供了很好的基础数据。