北太平洋副热带模态水盐度的年代际变化

副热带模态水(Subtropical Mode Water;STMW)在气候变化中起着重要作用。本文利用全球高分辨率数值模拟结果,研究了北太平洋STMW核心层盐度(Core Layer Salinity;CLS)的年代际变化及其物理机制。结果表明,CLS存在显著的年代际变化,其空间分布则与背景流场分布特征有关。侵蚀区CLS滞后生成区CLS约1~2年,这主要是海流平流输运引起的。生成区内,STMW的季节循环一般可分为生成期(12-4月)、隔离期(5-6月)和侵蚀期(7-11月),生成期混合层盐度(Mixed Layer Salinity;MLS)决定着隔离期和侵蚀期的CLS,而MLS年代际变化则主要由同太平洋年代际涛动存在负相关性的海表面淡水通量的变化引起。     

Designing a spatial pattern to rebalance the orientation of development and protection in Wuhan

Patterns of spatial development and protection form a basic category of geoscience,and redesigning them is a popular subject of research in regional sustainable development that is important for ecological civilization construction.The authors here report a case study of Wuhan city using the circuit theory model and minimum cumulative resistance(MCR)model to rebalance its spatial protection and development.The results show the following:(1)Using the density of the gross domestic product(GDP),density of population,rate of urbanization,and access to transportation as evaluation indicators,seven core areas of development in Wuhan were identified,accounting for 59%of the total number of streets,that exhibited a “circular-satellite”spatial structure.(2)According to the importance of ecosystem services,ecological sensitivity,land use type,and slope of the terrain,the resistance surface of spatial development in Wuhan had a stereoscopic spatial form of an“inverted pyramid,”with high surroundings and a low center.The area of low resistance accounted for 6.64%of the total area of Wuhan.(3)Based on coupling analysis using the MCR and spatial morphological characteristics of current,nine axes of spatial development with a total area of 427.27 km2 and eight key strategic points with a total area of 40.02 km2 were identified.Streets that were prioritized for development accounted for 9.63%of Wuhan's total area.(4)By combining the characterization of the development axis with the structure of the three-level core area,we extracted the structure of spatial development of "one heart,two wings,and three belts" in Wuhan.The research framework and empirical results can provide scientific guidance for the urban spatial layout,the development of regional linkages,and ecological environmental protection in China.     

青藏高原西部阿汝冰芯记录的近100 a气温变化研究

以2017年9月钻取自青藏高原西部阿汝冰崩区长度55.29 m的阿汝冰芯为研究对象,通过冰芯δ18O记录与Nye模型重建了冰芯上部17.87 m的时间序列是1917—2016年.结合冰芯邻近的改则、狮泉河气象站1973—2016年夏季平均气温数据,通过相关性分析及线性回归法、Mann-Kendall(M-K)检验分析,...     

有机质对海底沉积物中粘土矿物X射线衍射分析结果的影响

X射线衍射法广泛应用于分析粘土矿物的含量和结晶特征,由于粘土矿物易与有机质结合形成有机-粘土复合体,是否去除有机质对分析结果有很大影响,实验结果表明影响最大的是伊-蒙混层矿物(含蒙脱石)和伊利石的含量,为得到可靠实验数据,必须重视对样品的前处理工作,对不同批次样品应该保持一致的处理程序。     

基于HYCOM再分析数据研究琉球海流的形成与起源

The origin of the Ryukyu Current(RC) and the formation of its subsurface velocity core were investigated using a 23-year(1993–2015) global Hybrid Coordinate Ocean Model(HYCOM) dataset. The volume transport of the RC comes from the Kuroshio eastward branch(KEB) east of Taiwan and part of the North Pacific Subtropical Gyre(pNPSG). From the surface to 2 000 m depth, the KEB(p-NPSG) transport contributes 41.5%(58.5%) to the mean total RC transport. The KEB originally forms the subsurface velocity core of the RC east of Taiwan due to blockage of the subsurface Kuroshio by the Ilan Ridge(sill depth: 700 m). Above 700 m, the Kuroshio can enter the East China Sea(ECS) over the Ilan Ridge, meanwhile, the blocked Kuroshio below 700 m turns to the right and flows along the Ryukyu Islands. With the RC flowing northeastward, the p-NPSG contribution strengthens the subsurface maximum structure of the RC owing to the blockage of the Ryukyu Ridge. In the surface layer, the pNPSG cannot form a stable northeastward current due to frequent disturbance by mesoscale eddies and water exchange through the gaps(with net volume transport into ECS) between the Ryukyu Islands.     

基于特征点匹配及提纯的点云配准算法

针对传统的基于ICP点云配准算法配准时间长、收敛慢、需要较好初始配准等限制,本文利用现有的点云特征提取算法和描述算法,提取并匹配点云中的特征点,用RANSAC算法结合坐标转换模型剔除误匹配点对,用匹配点对在两点云中的坐标计算之间的坐标转换参数,从而实现点云的配准。相比ICP类算法,提高了点云配准的效率,同时提高了点云配准的自动化程度。     

Testing the stereoscopic precision of a large-format digital camera

The use of large-format digital cameras in aerial photogrammetry is leading to great improvements in photogrammetric production. Since they were first introduced about 10 years ago, the technological community has been testing and investigating the conditions under which this major change can be consolidated. But a certain (and understandable) bias may be noticed in the efforts that developers, researchers and clients are undertaking. Almost all of the efforts aim at checking the quality of automated measurements and very little attention has been directed to stereoscopic measurements by human operators, which, nevertheless, still represent an important task that needs to be carried out in the production chain. This paper presents the results from a number of tests (13 operators from a variety of enterprises) performed to check the stereoscopic precision of Vexcel UltraCamD camera images compared with Leica RC30 film images. The main conclusion to be drawn from the empirical data is that stereoscopic precision does not depend on the type of camera.     

基于采样方差的卫星钟信号分析

对原子钟频率稳定度分析受到频率漂移的影响进行定性分析,明确了不同类型方差在原子钟频率稳定度分析中的适用范围,首次提出将重叠Hadamard方差应用于卫星钟信号分析。分别利用Allan方差、Hadamard方差和重叠Hadamard方差对铷钟进行了稳定度计算,结果表明Allan方差的计算结果受频率漂移影响很大,而Hadamard系列方差能够有效克服频率漂移的影响,对于卫星钟的性能表征具有良好的效果。     

大气湍流对天基遥感系统地面分辨率的影响

分辨率是所有光学成像系统最重要的技术指标之一。当成像系统与待成像目标之间存在大气湍流时,后者便会在不同程度上影响图像分辨率。天基光学遥感更加关心大气湍流对目标地面分辨率的影响。从大气湍流相干长度和到达角起伏两个角度,通过详细的公式推导和数值计算,分别讨论天基光学遥感系统成像过程中湍流对图像地面分辨率的影响。结果表明,地面分辨率0.5 m以上的甚高分辨率遥感成像需要考虑大气湍流因素。     

深圳湾海域表层和柱样沉积物中的重金属分布特征

分析深圳湾表层沉积物中锌、铬、镉、镍、铅、铜等6种重金属元素的含量发现它们的浓度均值已全部超过广东省海岸带沉积物背景值。根据潜在生态危害法,在6种重金属中镉造成的污染最严重,从潜在的生态危害指数评价看镉的含量已达到很高的污染水平。从面状分布看,重金属污染危害指数值在深圳河口区最低,在蛇口段居中等水平,在深圳湾内侧的近岸水域最大。柱样沉积物的浓度变化以1950年为界划分为两部分:1950年以来的现代沉积物中有较强的人类活动干扰痕迹,表现为重金属元素的浓度增长幅度大,且浓度很高,其均值全部大于广东省海岸带的背景值;1950年以前的近代沉积物中有稍弱的人类活动干扰痕迹。研究认为沉积物粒度特征、沉积速率、人类活动与重金属在沉积物中的浓度高低有直接相关关系,并直接影响到重金属在沉积物中的污染水平。