用于GNSS的SpT星载原子钟及时间系统介绍

研究了空间铷钟和被动型氢钟的地面批量和寿命试验测试结果,以及卫星在轨试验所达到的最新性能结果。基于这些星载钟的试验结果,对全球卫星导航系统的地面时间站的关键设备及其相关算法作了简要描述,并介绍了一种新颖的在轨技术,即从星载原子钟组（ONCLE）直接产生高度稳健的时间频率信号。     

陕西凤县地质灾害易发性评价研究

区域地质灾害易发性评价是地质灾害早期预警的基础.为了探索秦岭山区区域地质灾害易发性评价方法,文中在陕西凤县1:5万地质灾害详细调查和数据库建设的基础上,详细分析了地质灾害的发育分布规律及影响因素,利用GIS技术结合信息量模型方法完成了凤县地质灾害的易发性评价区划.结果显示:凤县地质灾害分布主要与河流侵蚀、植被覆盖率及人...     

Preface to the Special Issue on Antarctic Meteorology and Climate:Past,Present and Future

The Antarctic,including the continent of Antarctica and the Southern Ocean,is a critically important part of the Earth system.Research in Antarctic meteorology and climate has always been a challenging endeavor.Studying and predicting weather patterns in the Antarctic are important for understanding their role in local-to-global processes and facilitating field studies and logistical operations in the Antarctic(e.g.,Walsh et al.,2018).Studies of climate change in the Antarctic are comparatively neglected compared to those of the Arctic.However,significant climate changes have occurred in the Antarctic in the past several decades,i.e.,a strong warming over the Antarctic Peninsula even with a recent minor cooling,a deepening of the Amundsen Sea low,a rapid warming of the upper ocean north of the circumpolar current,an increase of Antarctic sea ice since the late 1970s followed by a recent rapid decrease,and an accelerated ice loss from the Antarctic ice shelf/sheet since the late 1970s(e.g.,Turner et al.,2005;Raphael et al.,2016;Sallée,2018;Parkinson,2019;Rignot et al.,2019).Investigating recent climate change in the Antarctic and the underlying mechanisms are important for predicting future climate change and providing information to policymakers.     

断层网络方向特征及其自组织演化

断层网络可视为一浅源构造地震的蕴震系统。地震前兆是该系统在演化过程中所表现出来的复杂的整体动态行为，是蕴震系统自组织演化的构造微动态。本文从信息合成观点出发，提出了方向信息合成方法（ＤｉｒｅｃｔｉｏｎＩｎｆｏｒｍａｔｉｏｎＳｙｎｔｈｅｓｉｓ）。对京、津、唐地区５０条跨断层地形变观测时间序列的计算表明：断层网络活动的方向特征（相对张、压、扭动等）临震前出现了运动方式（方向）群体优势异常；该异常可能具有可重复性，该方向特征的时空演化可视为一个自组织过程。     

Climate anomalies in the southern high latitudes associated with the Subtropical Dipole Mode

1　Introduction EnoughhasbeensaidabouttheteleconnectionofENSO(ElNi o SouthernOscilla tion)inthetropicalPacificOceanandtheclimateinthesouthernhighlatitudes(Fletcher etal.1982;SmithandStearns1993;SimmodsandJacka1995;Liuetal.2002;Kwok andComiso2002).Inres…     

地磁感应电流研究综述

因太阳活动而引起的地磁扰动,会在地球表面感生出地电场,从而在地表附近的导体系统中产生地磁感应电流(GICs).太阳表面的异常活动而引起的磁暴会导致强烈的GICs,严重威胁电信设备、电网、油气管道和铁路运输网络等基础设施系统的安全运行,已经成为最严重的空间天气灾害之一.因此,对GICs进行深入研究以建立对其做出迅速预测的能力,在科学和应用方面都有重要意义.本文综述了GICs的研究进展,从引入空间天气的概念开始,将GICs作为从太阳活动到太阳风再到地球扰动的空间天气链的最终环节;重点阐述了GICs的计算中所涉及的三个步骤:地球表面地磁场重建、感应地电场的计算,以及地面导体系统中GICs计算;对每一步骤中主要方法的相关原理和应用做了简要介绍与评估;最后总结了当前GICs的研究现状,并对未来GICs的研究方向与挑战进行了展望.     

The integrated impacts of natural processes and human activities on groundwater salinization in the coastal aquifers of Beihai,southern China

Salinization in coastal aquifers is usually related to both seawater intrusion and water–rock interaction. The results of chemical and isotopic methods were combined to identify the origin and processes of groundwater salinization in Daguansha area of Beihai, southern China. The concentrations of the major ions that dominate in seawater (Cl^?, Na⁺, Ca²⁺, Mg²⁺ and SO ₄ ^2– ), as well as the isotopic content and ratios (²H, ¹⁸O, ⁸⁷Sr/⁸⁶Sr and ¹³C), suggest that the salinization occurring in the aquifer of the coastal plain is related to seawater and that the prevailing hydrochemical processes are evaporation, mixing, dissolution and ion exchange. For the unconfined aquifer, groundwater salinization has occurred in an area that is significantly influenced by land-based sea farming. The integrated impacts of seawater intrusion from the Beibuwan Gulf and infiltration of seawater from the culture ponds are identified in the shallowest confined aquifer (I) in the middle of the area (site BBW2). Leakage from this polluted confined aquifer causes the salinization of groundwater in the underlying confined aquifer (II). At the coastal monitoring site (BBW3), confined aquifer I and lower confined aquifer II are heavily contaminated by seawater intrusion. The weak connectivity between the upper aquifers, and the seaward movement of freshwater, prevents saltwater from encroaching the deepest confined aquifer (III). A conceptual model is presented. Above all, understanding of the origin and processes of groundwater salinization will provide essential information for the planning and sustainable management of groundwater resources in this region.     

中心城区广场公园绿地可达性研究

城市广场公园绿地的可达性是间接反映其布局是否合理的重要指标。本文运用多中心性模型测度了武汉市中心城区公共交通网络中心性,研究了武汉市中心城区公共交通网络和广场公园绿地空间分布规律以及空间结构;并利用邻近度和中间性两个指标,进一步分析了武汉市中心城区广场公园绿地的空间可达性。结果表明武汉市中心城区广场公园绿地具有以下特点:1)整体分布呈现较强的集聚性,同时区域差异明显;2)邻近度与"距离"呈线性负相关,从中心城区的中心到边缘,广场公园绿地中间性整体呈逐渐下降的趋势;3)位于中心城区中心的广场公园绿地空间可达性最佳,其覆盖区域交通网络中心性较高,可达时间相对较短,位于人口分布中心周围的广场公园绿地可达性较好,且可达性由城区中心向城区边缘逐渐递减。     

Quaternary Sporopollen Records and Environmental Evolution in the Dalangtan of Qaidam Basin

正Since the Quaternary,very thick lacustrine sediments have been deposited in Dalangtan of Qaidam Basin.Based on a study of high-resolution sporopollen analysis on the Dalangtan ZK06 drilling,and paleomagnetic dating     

珠三角空间梯度葫芦藓的重金属含量及其环境指示意义

以珠三角空间梯度上的核心区广州、近郊区肇庆鼎湖及远郊区怀集三地的葫芦藓为研究对象,对其重金属污染进行研究。结果显示:珠三角地区葫芦藓重金属含量呈明显的梯级分布,其中Cu、Pb、Zn、Cr、Cd含量均表现为广州最高,分别为47.64、68.83、252.87、64.20和1.02mg/kg;肇庆次之,分别为36.34、40.51、143.49、51.29和0.64mg/kg;怀集最低,分别为16.42、11.80、97.13、32.43和0.21mg/kg。珠三角地区葫芦藓内不同重金属的含量差异反映了来源差异,其中Cd、Pb、Zn和Cu之间呈显著正相关关系,反映了重金属元素来自于相同的污染源;而Cr与Cd、Pb、Cu和Zn的相关性相对弱一些,说明Cr的污染源与其他元素存在一些差异,或者说这个元素与其他元素同时污染大气的可能性相对小一些。分析进一步揭示,三地葫芦藓污染同三地大气污染以及工业化进程存在一定的耦合性。基于此,指出葫芦藓可作为研究环境污染的指示标志,具有重要的环境指示意义。