A comparison of methods to estimate groundwater recharge from bare soil based on data observed by a large-scale lysimeter

Effectively estimating groundwater recharge is critical to manage water resources, especially in arid and semi-arid regions as impacted by intensive human activities and climate changes. Rare insights have been gained into groundwater recharge since direct observation is hard to carry out. Although several methods are currently available to estimate groundwater recharge, the estimated results may cover noticeable bias. The behaviours of different methods based on different conceptual frameworks and exhibiting different levels of complexity should be examined to estimate actual groundwater recharge. This study aims to assess the performance of four common methods to estimate groundwater recharge. For this end, large-scale lysimeters equipped with soil water content sensors and water table sensors were set up at a research site established in Guanzhong Basin of China. The data achieved by 1-year observation were employed to compare four estimation methods. As revealed from the results, the following findings are drawn. (a) Groundwater level fluctuation (GLF) method is simple, whereas its accuracy is determined by specific yield, and adopting a water balance method to estimate specific yield can considerably enhance the accuracy of GLF. (b) The calibrated numerical model can obtain the optimal result compared with the other methods, whereas long-term observation data are required for parameter calibration. (c) In the water balance method, the maximum entropy production (MEP) model and a practical method (estimating evaporation between two rainfall events) were used to calculate evaporation. As indicated by the results, water balance method combined with MEP is capable of obtaining more reliable results of groundwater recharge compared with the practical method. (d) With an analytical model based on linearized Richards' equation, accurate results can be achieved. What is more, the analytical model only needs the measurement of soil moisture near the surface. The limitation of this method is that it is difficult to determine the maximal water flux. The mentioned findings are of critical implications to the management and sustainable development of groundwater.     

基于加权贝叶斯网络的海洋灾害风险评估

全球气候变化背景下,海洋灾害的群发性、难以预见性和灾害链效应日显突出,造成的损失逐年上升,开展海洋灾害的风险评估工作至关重要。针对海洋灾害评估中的不确定问题,本文首先基于风险理论剖析了海洋灾害风险的不确定性特征,构建了灾害评估指标体系;然后基于贝叶斯网络模型,提出针对不确定性灾害评估的风险贝叶斯网络,进而基于主客观定权,构建了加权贝叶斯网络评估模型;最后对我国沿海地区海洋灾害开展评估研究。实验表明,该评估模型有效实现海洋灾害的风险评估,具有实际可操作性。     

基于无人机MiniSAR和正射影像的海岸带开发利用信息提取对比研究

近年来,海洋在沿海国家的战略地位空前提升,海洋遥感技术也被广泛应用。海洋遥感利用电磁波与大气和海洋的相互作用原理,从卫星平台观测和研究海洋海岸带的各种现象,从而获取海岸带信息,分析海岸带变化。文章基于GIS和遥感技术,利用无人机搭载微型合成孔径雷达(MiniSAR)获取高分辨率SAR影像并与无人机光学正射影像进行对比研究,获取了海岸带开发利用信息分布状况,分析了两种手段获取结果的差异性原因,为深入开展无人机遥感监测在海洋管理中的应用奠定了基础。利用无人机机动灵活的特点,宏观、快速、高效地获取海岸带信息,并实时监测海岸带动态变化,将为海洋综合管理、海洋经济发展、海洋环境保护提供基础数据和技术支撑。     

空-谱融合的条件随机场高光谱影像分类方法

高光谱遥感数据具有光谱信息丰富、图谱合一的特点,目前已经广泛地应用在对地观测中。传统的高光谱分类模型大多过分依赖影像光谱信息,没有充分利用空间特征信息,这使得分类精度还有很大的提升空间。条件随机场是一种概率模型,能够较好地融合空间上下文信息,在高光谱影像分类中已经得到越来越多的关注,但大部分条件随机场模型存在超平滑的现象,会导致影像细节丢失。针对该问题,本文提出了一种优化融合影像空-谱信息的高分辨率/高光谱影像分类方法,该方法将影像的纹理信息与原始光谱信息进行融合,利用SVM分类器对其进行预分类,并将各类概率定义为一元势函数,以融合空间特征信息;然后将空间平滑项和局部类别标签成本项加入二元势函数中,以考虑空间背景信息,并保留各类别中的详细信息。最后,通过两组的高分辨率/高光谱影像数据进行试验。结果表明,与SVM算法、传统的条件随机场方法和面向对象的分类方法相比,本文提出的算法在整体分类精度上分别提高了10%、9%和8%以上,同时在保持地物边缘完整性、避免“同谱异物”与“同物异谱”的现象方面有较明显的优势。     

尼泊尔地震的NOAA卫星数据震前异常分析

发生地震时常伴随有地热辐射增强现象,这些异常信息隐藏于遥感卫星NOAA所捕获的地球射出长波辐射（OLR）数据中,目前多数研究还停留在对源数据的解读,缺乏有效的信息处理技术,致使大部分的OLR数据没有得到充分利用。因此,本文提出一种基于鞅理论的概率统计方法来识别异常特征算法,从有噪声的非结构化的源数据中提取出震前OLR数据异常变化特征序列,从时间序列和地域范围进行震前异常分析。本算法实验是以尼泊尔的在2014年9月至2015年7月期间（包括2015年4月25日Ms7.8大地震）发生的3次地震的OLR数据为例,实验结果显示震中区域的OLR数据在震前的2~3个月开始有显著的异常数据变化,通过分析发现数据显示数据异常在震前出现的时间长短与地震的大小相关,异常的发生区域与震区周围的地貌特征相关。这说明基于鞅理论的算法所提取的OLR数据异常点序列的确与地震发生的时间地点是有关系的。     

FME和VSFTP相结合的不动产数据模式探讨

以实际项目应用为例，阐述了一种FME和VSFTP相结合的不动产数据整合作业模式。该模式通过团队协作，快速迭代更新数据，具有工作效率较高、工作进度可控、数据质量较好的特点，为不动产数据质量相对较差的地区提供了一套可行的数据整合工作模式，该模式也可推广应用到三调内业数据处理。     

Reverse-Time Migration of Converted S-Waves of Varying Densities

Ocean-Bottom Node(OBN) acquisitions provide both non-converted and converted reflection energy. There is a clear advantage to independently imaging both P-and S-waves, as they provide more information collectively than either does alone. In many conventional converted-wave pre-stack migration algorithms, density is treated as a constant, which is not the real-life case on earth. S-wave velocity and density information is crucial for hydrocarbon detection because it helps in the identification of porefilling fluids. In this paper, we focused on the effect of density on imaging, and developed a method of reverse-time migration(RTM) on converted s-waves of varying densities(VD-RTMCS). Phase correction was required prior to pre-stack migration to avoid constructive interference between data from adjacent sources. Synthetic data examples showed that when density variations were included, image profiles showed advantages in signal-to-noise ratio, vertical resolution and imaging of complex structures.     

再探温跃层有孔虫B/Ca与温度和[CO32-]的依赖性及其在24 ka以来热带西太平洋次表层碳酸盐系统重建中的应用

The B/Ca ratio of planktonic foraminifer shells has been used as a proxy for reconstructing past ocean carbonate chemistry. However, recent studies have revealed significant uncertainties associated with this proxy, such as whether seawater temperature or [ CO_3~(2-)] is the dominant control on the partition coefficient(K_D) of planktonic foraminiferal B/Ca. To address these uncertainties and thus improve our understanding of the planktonic foraminiferal B/Ca proxy, we analysed B/Ca ratios in the tests of Neogloboquadrina dutertrei(300–355 μm) and Pulleniatina obliquiloculata(355–400 μm) in surface sediment samples from the tropical western Pacific and South China Sea. The relationship between these B/Ca ratios and bottom water calcite saturation states(Δ[ CO_3~(2-)]) is weak, thus suggesting only a small dissolution effect on the B/Ca of the two species. The correlation coefficients(R~2) between the B/Ca ratios of N. dutertrei and P. obliquiloculata and environmental parameters(e.g., temperature, salinity, phosphate, DIC and ALK) in the tropical western Pacific and South China Sea are not high enough to justify using B/Ca ratios as a palaeoenvironmental proxy in the study areas. The significant correlation between K_D values of N. dutertrei and P. obliquiloculata and carbonate system parameters(e.g.,[ CO_3~(2-)], DIC, ALK, pH and [ HCO_3~-]) in the study area reflect chemical links between the K_D denominator and these variables. Based on our surface sediment calibration, an empirical relationship between the K_D of N.dutertrei and temperature is proposed in the tropical western Pacific. We also generated a record of B/Ca ratios in N. dutertrei(300–355 μm) from Core MD06-3052 in the tropical western Pacific over the past 24 ka to evaluate the application of the revised B/Ca proxy method. Based on the reconstructed empirical relationship for B/Ca and subsurface seawater ALK, we estimated subsurface seawater carbonate system parameters in the tropical western Pacific since 24 ka. In general, the estimated subsurface seawater pH and [ CO_3~(2-)] show an increase with time, and the record of subsurface seawater pCO_2 shows a decrease with time, in the tropical western Pacific over the past 24 ka. The consistent trends in subsurface seawater pCO_2 and opal flux during deglaciation may imply that the reported increase in subsurface water pCO_2 in the study area was promoted by enhanced upwelling in the Southern Ocean.     

Extracting invariant characteristics of sketch maps: Towards place query‐by‐sketch

In geography, invariant aspects of sketches are essential to study because they reflect the human perception of real‐world places. A person's perception of a place can be expressed in sketches. In this article, we quantitatively and qualitatively analyzed the characteristics of single objects and characteristics among objects in sketches and the real world to find reliable invariants that can be used to establish references/correspondences between sketch and world in a matching process. These characteristics include category, shape, name, and relative size of each object. Moreover, quantity and spatial relationships—such as topological, ordering, and location relationships—among all objects are also analyzed to assess consistency between sketched and actual places. The approach presented in this study extracts the reliable invariants for query‐by‐sketch and prioritizes their relevance for a sketch‐map matching process.     

测绘地理信息档案管理对策研究

国民经济建设对测绘地理信息档案的需求旺盛,如何对测绘地理信息数据进行归档管理,提高测绘地理信息档案存储的安全性及方便再利用,已经成为测绘地理信息档案管理部门需要研究的重要课题。本文通过分析当前测绘地理信息档案管理的现状,指出存在的问题,提出有力的改进措施。