New aspects for new generation telescopes     

Eva K. Grebel 《Astrophysics and Space Science》2003,284(2):947-956

A selection of future observing facilities relevant to galaxy evolution science covering the wavelength range from X-rays to the radio regime are summarized. Scientific aspects that can be investigated with these next generation telescopes are briefly discussed. While prospects look bright for highly advanced and innovative future facilities, it will be important to ensure that human resources in observational astronomy and theory – both in terms of expertise, funding, and available positions – are keeping pace with the technological developments. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

关于《大气环流的若干基本问题》     

吕建华 《大气科学》2016,40(1):78-85

本文简要回顾了《大气环流的若干基本问题》的主要内容.以书中部分内容为例,通过和近期大气环流理论的进展相联系,指出叶笃正和朱抱真在书中表达的主要观点,如对大型涡旋在经圈环流中的第一性作用及其作为联系大气环流各主要成员和物理量输送中心环节的认识,对大型涡旋涡度输送在急流形成和维持中作用的强调,以及对大气环流成员和过程的内在统一性的认识等等,能为后来的理论进展所证实,或者和后来的理论互为补充.两位作者对大气环流物理本质和整体图像的深刻理解对大气环流理论的进一步发展以及理解气候变化的基本动力学依然具有现实的意义.  相似文献   

High resolution multisensor fusion of SAR,optical and LiDAR data based on crisp vs. fuzzy and feature vs. decision ensemble systems     

《International Journal of Applied Earth Observation and Geoinformation》2016

Synthetic Aperture Radar (SAR) data are of high interest for different applications in remote sensing specially land cover classification. SAR imaging is independent of solar illumination and weather conditions. It can even penetrate some of the Earth’s surface materials to return information about subsurface features. However, the response of radar is more a function of geometry and structure than a surface reflection occurs in optical images. In addition, the backscatter of objects in the microwave range depends on the frequency of the band used, and the grey values in SAR images are different from the usual assumption of the spectral reflectance of the Earth’s surface. Consequently, SAR imaging is often used as a complementary technique to traditional optical remote sensing. This study presents different ensemble systems for multisensor fusion of SAR, multispectral and LiDAR data. First, in decision ensemble system, after extraction and selection of proper features from each data, crisp SVM (Support Vector Machine) and Fuzzy KNN (K Nearest Neighbor) are utilized on each feature space. Finally Bayesian Theory is applied to fuse SVMs when Decision Template (DT) and Dempster Shafer (DS) are applied as fuzzy decision fusion methods on KNNs. Second, in feature ensemble system, features from all data are applied on a cube. Then classifications were performed by SVM and FKNN as crisp and fuzzy decision making system respectively. A co-registered TerrraSAR-X, WorldView-2 and LiDAR data set form San Francisco of USA was available to examine the effectiveness of the proposed method. The results show that combinations of SAR data with different sensor improves classification results for most of the classes.  相似文献   

沈阳地区MODIS与MERSI气溶胶产品对比研究     

张婕  刘昊野  辛金元  张文煜  肖国杰  冯鑫媛  王莉莉 《遥感学报》2016,20(4):549-560

在中国东北地区,卫星气溶胶产品尚缺乏有效的验证机制,相关应用存在较大不确定性。利用2009–2011年中国地区太阳分光光度计观测网(CSHNET)沈阳站地基观测资料,借助后向轨迹模式分析了该地区气溶胶来源和季节变化特征,并同步对比了FY-3A/MERSI和Terra/MODIS气溶胶产品精度的季节差异及误差来源。结果表明:沈阳站气溶胶光学厚度和Angstrom波长指数季节变化明显,气溶胶受远程输送和区域排放的共同影响,人为源和自然源丰富。不同粒径粒子对气溶胶光学厚度的贡献因季节而异,导致卫星反演算法中气溶胶模型选择误差较大,影响了卫星反演精度。观测期间MODIS与MERSI气溶胶产品与地基观测数据的总匹配率分别为68%和83%。当气溶胶光学厚度较低时(AOD0.35),MODIS产品出现低估,MERSI出现高估,与实测值的相对误差分别为–46%—54%、7%—135%;当气溶胶光学厚度较高时(0.35—0.75),MODIS和MERSI均出现不同程度的低估,两者与实测值的相对误差分别为–34%—54%、–21%—75%;当气溶胶光学厚度大于0.75时,低估尤为严重,与实测值的相对误差可达–34%—100%、–9%—58%。能与地基观测匹配的MODIS和MERSI有效样本数春、秋季较高(春季分别为69%、80%,秋季分别为73%、70%),夏季次之(69%、73%),冬季最少(2%、49%);MODIS与地基观测的相关性总体优于MERSI;但在冬季,MODIS与MERSI产品均不具备代表性。MODIS与MERSI气溶胶产品落入误差线的比例均为春季最高(22%、25%),秋季次之(19%、16%),夏季最小(6%、5%)。MERSI对粗模态气溶胶(α≤0.5)反演效果优于MODIS,而MODIS对混合模态气溶胶(0.5≤α1.5)反演效果优于MERSI。MERSI与MODIS气溶胶产品在春、秋季可比性较好,夏季可比性较差,总体来说,春、秋季MERSI比MODIS低估更为严重。从气溶胶产品在辽宁省的区域分布来看,FY-3A/MERSI比Terra/MODIS覆盖范围略广,各季节FY-3A/MERSI与Terra/MODIS的总体空间分布特征基本一致,但对于某些地区,两者数值上依然存在较大偏差。  相似文献   

中国东部气溶胶光学厚度季节变化的数值模拟     

李嘉伟  韩志伟 《遥感学报》2016,20(2):205-215

气候模式对气溶胶光学厚度AOD的合理模拟,是模拟研究气溶胶气候效应的前提。利用在线耦合的区域气候—大气化学—气溶胶耦合模式系统RIEMS-Chem,模拟研究了2010年中国东部地区AOD的季节变化情况。模拟结果与卫星搭载的中分辨率成像光谱仪(MODIS)的反演资料和地基气溶胶观测网(AERONET)的站点观测资料分别进行了一年四季的详细对比,检验结果显示尽管模拟值有所低估,模式仍然能够合理地反映AOD的季节变化情况和空间分布特征,与AERONET站点观测值相比,整体相关系数为0.6。MODIS反演和相应模拟结果均显示,中国东部地区AOD整体水平夏季最大,春季次之,秋、冬季最小,华北平原、四川盆地和华中地区是AOD的主要大值区。只考虑日间AOD时,其季节分布特征略有不同,在华北平原地区,日间AOD夏季最大(1.1—1.5),在长江中下游流域地区,日间AOD则在春季最大(1.1—1.7);在中国东部,日间AOD的大值在夏、冬两季分别主要分布在长江以北、以南地区,而在春、秋两季则主要位于长江中下游流域。  相似文献   

Fatal weather-related general aviation accidents in the United States     

Andrew J. Fultz 《自然地理学》2016,37(5):291-312

General, or private and non-commercial, aviation accidents produce more fatalities than any other aviation category within the United States. Despite advances in scientific understanding and technology since the early 1900s, weather causes concern for aviation safety, and little is known about the characteristics of fatal weather-related general aviation accidents. We provide a comprehensive spatiotemporal analysis of fatal weather-related general aviation accidents from 1982 through 2013 using data culled from the United States National Transportation Safety Board (NTSB). Weather was a cause or contributing factor in 35% of fatal general aviation accidents, of which 60% occurred while instrument meteorological conditions were present. Fatal weather-related general aviation accidents occur most frequently between October and April, on weekends, in early morning and evening periods, and along the West Coast, Colorado Rockies, Appalachian Mountains, and the Northeast. There has been a long-term reduction in weather-related general aviation accidents and fatalities since the 1980s; nonetheless, these accidents are still responsible for nearly 100 fatalities/year in the United States. This study provides pilots, academics, the Federal Aviation Administration, the NTSB, and other aviation organizations with information to advance mitigation efforts aimed at reducing future aviation-related accidents in the United States.  相似文献   

分省普通地理图数据建库与编研——以新世纪版《国家普通地图集》为例     

王桂芝  王东华  乔俊军  周文  朱秀丽  赵飞 《地理信息世界》2016,(3)

新世纪版《中华人民共和国国家大地图集》编研项目的重要成果之一是《国家普通地图集》,而《国家普通地图集》的主要内容是分省地理图。新版分省地理图的编研,本着"先建库、后制图"的设计理念,充分利用国家1:1000 000基础地理信息数据库成果,并采用基于数据库的自动配图技术。本文主要介绍分省地理图的成果形态、编制技术路线、工艺流程和关键技术等。  相似文献   

“十四五”中国分省经济发展、能源需求与碳排放展望——基于CMRCGE模型的分析     

李继峰  顾阿伦  张成龙  孙振清 《气候变化研究进展》2019,15(6):649-659

在梳理新常态以来各省经济布局发展以及能源需求特征的基础上,重点剖析了国家区域协调发展战略,并利用中国多区域动态可计算一般均衡模型（China Multi-Regional Computable General Equilibrium,CMRCGE）,对“十四五”时期各省经济社会发展、能源需求及碳排放进行了模拟分析。主要结论包括：(1)在区域协调发展战略指引下,预计到“十四五”末,中国将有13个省市人均GDP超过1.5万美元,16个省市人均GDP在1.0万~1.5万美元之间,各省经济有望实现平稳较快发展。(2)预计2025年各省能源需求总量可达54.5亿tce（由于数据原因,未测算西藏）,“十四五”年均增长约为1.5%,能源需求仍保持低速增长。同时能源需求的重心逐步从东部向中部转移,而西部地区能源大省的用能比重基本保持稳定,这与各地所处的经济发展阶段、区域协调发展战略导向基本一致。(3)“十四五”时期各省的碳排放（主要考虑能源利用碳排放）强度年均降幅约为5.4%,绝大部分省份降幅超过4.0%。近年来碳强度显著下降的趋势有望继续保持。  相似文献   

Late Quaternary lake level record of Orog Nuur,southern Mongolia,revealed by optical dating of paleo-shorelines     

《Quaternary Geochronology》2022

The Late Quaternary hydroclimatic evolution of lake systems in Mongolia remains unclear. Here we present a record of lake level variations at Orog Nuur in the Valley of Gobi Lakes in southern Mongolia, since the last interglaciation, based on paleo-shoreline dating using quartz optically stimulated luminescence (OSL) and K-feldspar post-infrared infrared stimulated luminescence (pIRIR) signals. Due to feldspar contamination that could not be eliminated, the OSL signals of quartz single-aliquots (SA), except for two Holocene samples, were unsuitable for dating and a double SA regenerative-dose (SAR) protocol was used for the quartz fraction of these two samples. The pIR₅₀IR₁₇₀ and pIR₂₀₀IR₂₉₀ signals of K-feldspar SA were used to date Holocene samples and old samples (>100 ka), respectively, with the SAR protocol. To determine the bleaching condition of the pIR₂₀₀IR₂₉₀ signals, the first pIRIR dating of K-feldspar single-grains of lake shoreline sediments in Mongolia was performed. The equivalent doses of K-feldspar grains show normal distributions, suggesting that the pIR₂₀₀IR₂₉₀ signals are well-bleached. Overall, the results, combined with those of previous studies, show that a mega-lake developed at 56 m above the modern lake level (a.m.l.) during MIS 5e (124.2 ± 6.8–114.7 ± 8.0 ka). Holocene high-stands occurred in the last deglaciation–early Holocene (11.1 ± 1.0 ka) at 23 m a.m.l. and in the mid-Holocene (6.7 ± 0.8–3.3 ± 0.4 ka) at 20–14 m a.m.l. The dimensions of the paleo-lakes were recovered, and a hydrological index indicates that the effective moisture during MIS 5e and the mid-Holocene was 10.7 times and 3.6–5.0 times larger than today, respectively. Finally, the possible mechanisms behind the lake level history are discussed based on correlation with independent paleoclimatic records.  相似文献   

Synergy of airborne LiDAR and Worldview-2 satellite imagery for land cover and habitat mapping: A BIO_SOS-EODHaM case study for the Netherlands     

《International Journal of Applied Earth Observation and Geoinformation》2015

A major challenge is to develop a biodiversity observation system that is cost effective and applicable in any geographic region. Measuring and reliable reporting of trends and changes in biodiversity requires amongst others detailed and accurate land cover and habitat maps in a standard and comparable way. The objective of this paper is to assess the EODHaM (EO Data for Habitat Mapping) classification results for a Dutch case study. The EODHaM system was developed within the BIO_SOS (The BIOdiversity multi-SOurce monitoring System: from Space TO Species) project and contains the decision rules for each land cover and habitat class based on spectral and height information. One of the main findings is that canopy height models, as derived from LiDAR, in combination with very high resolution satellite imagery provides a powerful input for the EODHaM system for the purpose of generic land cover and habitat mapping for any location across the globe. The assessment of the EODHaM classification results based on field data showed an overall accuracy of 74% for the land cover classes as described according to the Food and Agricultural Organization (FAO) Land Cover Classification System (LCCS) taxonomy at level 3, while the overall accuracy was lower (69.0%) for the habitat map based on the General Habitat Category (GHC) system for habitat surveillance and monitoring. A GHC habitat class is determined for each mapping unit on the basis of the composition of the individual life forms and height measurements. The classification showed very good results for forest phanerophytes (FPH) when individual life forms were analyzed in terms of their percentage coverage estimates per mapping unit from the LCCS classification and validated with field surveys. Analysis for shrubby chamaephytes (SCH) showed less accurate results, but might also be due to less accurate field estimates of percentage coverage. Overall, the EODHaM classification results encouraged us to derive the heights of all vegetated objects in the Netherlands from LiDAR data, in preparation for new habitat classifications.  相似文献