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AIRS遥感观察三峡库区二氧化碳浓度变化特征 总被引：1，自引：0，他引：1
本文采用AIRS仪器遥感观察获得的2003至2010年CO2产品L3数据的月平均结果,分析了三峡库区CO2浓度的时空变化特征。选择三峡库区周边9个网格点,结果表明2003至2010年三峡库区周边区域CO2浓度有明显的季节变化和逐年增加的趋势。8年平均增加量与全国大气CO2浓度增加量一致。不同地区CO2浓度与平均浓度的偏差均在仪器测量误差范围以内,未发现不同地区CO2浓度分布和变化规律有明显的差异。 相似文献
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《西藏科技》2016,(5)
利用753站月资料中近30年西藏降水资料,做出西藏近30年累计降水趋势,结果发现:近30年来西藏的年降水量呈不显著的增加趋势。再利用1981~2010年NCEP再分析月平均高度场资料,定义了东伸指数以确定100hPa高度上南亚高压的东西位置,运用功率谱分析找出南亚高压东西振荡的周期。并选出东西位置异常年份进行合成分析,讨论了夏季南亚高压东西位置异常时对应的高低空以及未来一年内的环流形势的特征。最后利用西藏27个测站30年的降水资料对偏东年和偏西年的降水特征进行分析。还有利用1979~2008年NCEP在分析月平均高度场和风场资料,分析南亚高压各指数的年际变化,并且各指数间作相关与西藏夏季降水的关系。 相似文献
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本文使用全国160站逐月降水资料及NCEP/NCAR再分析资料月平均数据集,采用滑动平均和合成分析方法,分析了江淮流域24个代表站1951-2012年夏季雨量的年代际变化特征.结果表明,近60年来江淮地区夏季降水存在明显的年代际变化特征。通过对西太平洋副热带高压的合成分析,发现江淮流域梅雨期雨量与西太平洋副热带高压关系密切。主要表现为,当副高位置偏西强度偏大时,江淮地区夏季雨量增多;反之,则雨量偏少。 相似文献
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青藏高原是世界上总辐射量最高的地区,也是全球超太阳常数的极值区域之一。此处形成了一个"嵌入"对流层中部大气的巨大的热源,可以伸展到自由大气,其超越了世界上任何超级城市群落所产生的中空热岛效应,对全球与区域大气环流系统变化的动力"驱动"产生了难以估计的效应。与地形热力过程季节变化密切相关的亚洲夏季风是世界上范围最广和强度最强的季风;从冬季到早春季节转换过程中,由于太阳辐射的影响造成青藏高原大地形感热的"快速响应"及其相对高值动态移动,在盛夏梅雨及其云降水带前沿线恰好停滞于中国"三阶梯"地形分布山地—平原过渡区。此现象表明,青藏高原可能扮演着夏季风过程陆地—海洋—大气相互作用的关键角色。中国区域低云量与总云量极值区均与青藏高原大江大河的源头(长江、澜沧江、雅鲁藏布江等)、中东部湖泊群与冰川集中区空间分布几乎吻合,这表明"亚洲水塔"形成的关键因素与"世界屋脊"特有的云降水结构不可分割。研究表明,青藏高原大气热源对局地与下游区域云降水过程水汽输送流型等均有显著影响。长江流域降水与全国低云量存在一个明显沿长江流域的带状高相关结构,充分表明长江流域降水与上游"亚洲水塔""热驱动"以及对流系统具有重要相关关系。从跨赤道经向环流的视角可发现,夏季南、北半球跨赤道气流低层强偏南、高层强偏北气流出现在东亚地区和北美区域两大地形对应的赤道区,这2个跨赤道极值区恰与青藏高原、落基山高原位置相对应。青藏高原纬向与经向环流圈结构与区域-全球大气环流相关机制,印证了"世界屋脊"隆起大地形的"热驱动"及其对流活动在全球能量、水分循环的作用。青藏高原特殊水汽三维结构分布和跨半球的纬向和经向大气垂直环流图表明青藏高原对全球尺度大气环流变化的贡献显著。文章进一步以东亚、全球水循环的视角,提出了青藏高原作为全球性大气"水塔"的观念,认为在高原地区一个水塔的"供水"和"蓄水"循环体系,特别是高原地表冰川、积雪和湖泊作为"蓄水池"系统,使得所有的河流可作为"输水管道",将"水塔"的水向周边区域输送出去,高层大气也提供向外输送的渠道。青藏高原特殊的跨半球大气水分循环可构建"世界水塔"与其周边地区独特的水文功能概念,综合描绘了青藏高原"世界水塔"及其地球上一个完整的行星尺度陆地—海洋—大气水分循环物理图像。 相似文献
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近50年秋季全球旱涝年的分布特征及其与海温和ENSO的关系 总被引：1，自引：0，他引：1
该文用Chen等(2001)最新创建的全球陆地月降水资料(PREC/L),划分并检验了1948年～2001年全球9月～11月的旱涝年.结果表明,冷事件大多对应涝年,暖事件大多对应旱年.全球9月～11月降水有明显的年代际变化,涝年大多在80年代以前,早年大多从80年代开始.其中,1987年～1997年全球9月～11月的连续早年,是一个非常特殊的时段.指出,印度季风区域、东南亚地区、热带太平洋岛屿、我国的东南沿海及日本一带、西非季风区及墨西哥湾区域,是旱涝年的平均降水差异较大的区域.并指出,东太平洋和西南太平洋3月～5月海温的变化对于9月～11月全球陆地降水的趋势变化有很好的预报意义.划分并检验了南、北半球9月～11月的旱涝年.指出,北半球旱涝年的分布和全球的是基本一致的,南半球与北半球的旱涝年的分布具有明显的正相关. 相似文献
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九寨沟、黄龙地区水资源的变化特征及成因分析 总被引：2，自引：0，他引：2
利用九寨沟、黄龙地区附近代表站的降水资料及NCEP/NCAR1959年～2004年共46年月平均再分析资料，采用小波分析、合成分析等方法对九寨沟、黄龙地区水资源的气候特征进行了研究。结果发现，九寨沟、黄龙地区的降水以及水资源的多年平均值分别为691mm、247mm，季节变化明显。46年来，该区年平均降水以及水资源的总趋势是减少的，20世纪80年代尤其是1994年以来减少趋势尤为显著；两者的减少主要发生在7月份。本区年水资源的年代际变化最显著，主要是15年左右的周期。九寨沟、黄龙地区7月份降水、水资源的变化与大气环流和南来水汽的变化有密切关系，主要的影响因子是巴尔喀什湖以东到贝加尔湖以南地区的500hPa高度场形势和来自南海西太平洋地区的偏南风水汽输送。高度场以及南来水汽两个主要因子的变化导致80年代尤其是1994年以来九寨沟、黄龙地区7月份降水显著减少，进而影响到全年降水，使其也呈减少趋势；降水的异常变化进一步引起了九寨沟、黄龙地区水资源的异常变化。 相似文献
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在2015年1月-2015年12月期间,本研究团队对贵州纳朵洞3处滴水点和1处池水点进行了为期一个水文年的监测和实验分析,并结合当地的气象资料,分析了各个滴水点的时空变化特征,初步探讨了洞穴滴水对外界气温和降水的响应机制。(1)洞穴滴水类型的不同导致对外界大气降水的响应机制存在差异,D4和D8为常年性滴水,响应较慢,D7为季节性滴水,响应较快。p H和电导率变化趋势大致相似,总体表现出夏季低、冬季高的特点,3处滴水点水中的CO2浓度变化趋势表现出一致性,呈现出夏季浓度高,冬季浓度低的特点,且存在一定的滞后性,滞后期大约为2个月,这与洞穴外界大气温度与降水的季节变化有关。(2)D4、D8、D7滴水点的土壤和岩层厚度逐渐递减,导致水-土-岩反应时间也随着减少,3处滴水点Ca~(2+)、Mg~(2+)、Ba~(2+)、Sr~(2+)的浓度变化也表现出逐级递减的特点,DC池水点由于夏季洞内CO2浓度较高,致使水中p H偏低,继续溶解下部基岩,进而致使水中Ca~(2+)的浓度偏高。(3)滴水点中Ca~(2+)、Mg2、Ba~(2+)、Sr~(2+)的浓度变化特征总体上表现随着降水的增加,浓度逐渐上升,雨季高于旱季的特点。在5月~10月份雨季期间,随着降水量的增加,各个滴水点Mg/Ca比值处于下降阶段,而在11月至次年4月旱季期间,随着降水量的减少,Mg/Ca比值处于增加阶段。 相似文献
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《中国科学院院刊(英文版)》2008,22(1):2-3
CAS should stick to the principle of rendering service to, and giving impetus for, the development of China＇s science enterprise by making S＆T innovations, said CAS President LU Yongxiang. The CAS president made the remarks in a recent talk to communicate the gist of the winter session of the Party＇s Leading-member Group at CAS, which was held from 7 to 11 January in Beijing. 相似文献
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《中国科学院院刊(英文版)》2008,22(1)
With great care, Dr. ZHOU Zhonghe takes out a package wrapped by cotton tissue from a drawer and says: "This is the gem of our collections: the fossil of a bird that lived 125 million years ago!" Then, pointing at a tiny mound, he explains: "Look, this is the claw and that is the head. It was in the egg shell and ready to hatch ... The species fell into a family of waterside inhabitants." 相似文献
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Marjorie Armstrong-Stassen Margaret Landstrom Ramona Lumpkin 《The Information Society》1998,14(2):153-164
This study examined how students who had no prior experience with videoconferencing would react to the use of videoconferencing as an instructional medium. Students enrolled in seven different courses completed a questionnaire at the beginning of the semester and again at the end of the semester. Students at the origination and remote sites did not differ in their reactions toward videoconferencing but there was a significant difference for gender. Women reacted less favorably to videoconferencing. Compared to the beginning of the semester, students reported significantly less positive attitudes toward taking a course through videoconferencing at the end of the semester. There were no significant differences in students' attitudes toward videoconferencing across courses at the beginning of the semester but there were significant differences across the courses at the end of the semester. The results suggest the need for better preparation for both students and instructors. 相似文献
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A joint study by Prof. ZHANG Zhibin from the CAS Institute of Zoology his co-workers from Norway US Swiss have indicated that historical outbreaks of migratory locusts in China were associated with cold spells suggesting that China's projected climate warming could decrease the pest's numbers. The study was published in Proceedings of the National Academy of Sciences on September .…… 《中国科学院院刊(英文版)》2008,22(1):6-7
Ajoint study by Prof. ZHANG Zhibin from the CAS Institute of Zoology and his co-workers from Norway, US and Swiss have indicated that historical outbreaks of migratory locusts in China were associated with cold spells, suggesting that China＇s projected climate warming could decrease the pest＇s numbers. The study was published in Proceedings of theNational Academy of Sciences on 17 September, 2007. 相似文献
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Caroline Haythornthwaite 《The Information Society》2001,17(3):211-226
A computer-mediated group is a complex entity whose members exchange many types of information via multiple means of communication in pursuit of goals specific to their environment. Over time, they coordinate technical features of media with locally enacted use to achieve a viable working arrangement. To explore this complex interaction, a case study is presented of the social networks of interactions and media use among members of a class of computer-supported distance learners. Results show how group structures associated with project teams dominated who communicated with whom, about what, and via which media over the term, and how media came to occupy their own communication niches: Webboard for diffuse class-wide communication; Internet Relay Chat more to named others but still for general communication across the class; and e-mail primarily for intrateam communication. Face-to-face interaction, occurring only during a short on-campus session, appears to have had a catalytic effect on social and emotional exchanges. Results suggest the need to structure exchanges to balance class-wide sharing of ideas with subgroup interactions that facilitate project completion, and to provide media that support these two modes of interaction. 相似文献
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Electronic data interchange (EDI) provides means for interorganizational communication, creates network externalities, requires an advanced information technology (IT) infrastructure, and relies on standards. In the diffusion of such innovations, institutional involvement is imperative. Such institutions contain governmental agencies, national and global standardization organizations, local government, and nonprofit private organizations like industry associations. The last type of organizations we call intermediating institutions. They intermediate or coordinate ("inscribe") the activities of a group of would-be adopters. Unfortunately, little is known of how these organizations shape the EDI diffusion trajectory. In this article we examine one specific type of intermediating organizations?industry associations?and how they advanced the EDI diffusion process in the grocery sectors of Hong Kong, Denmark and Finland. We identify six institutional measures, placed into a matrix formed by the mode of involvement (influence vs. regulation) and the type of diffusion force (supply push vs. demand pull), that can be mobilized to further the EDI diffusion. Industry associations were found to be active users of all these measures to varying degrees. Their role was critical especially in knowledge building, knowledge deployment, and standard setting. Furthermore, institutional involvement varied due to policy and cultural contingencies and power dependencies. 相似文献
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Puay Tang 《The Information Society》1998,14(1):19-31
The increasing prospects of digital piracy has prompted the perceived need by electronic publishers to adopt technical systems of protection, and governments to reform their copyright laws. This article is a preliminary study of the management of intellectual property by electronic publishers, defined as those involved in the production of online databases, and CD-ROMs. It focuses on three main issues: (1) how electronic publishers view the increasing threat of piracy; (2) the methods of protection employed to protect intellectual property in digital format; and (3) the importance of technological protection of intellectual property in electronic publications. The analysis is based on a sample of 23 UK electronic publishers. The interviews revealed an interesting assortment of protection methods and did not show that technological protection was a preferred way. Instead, the means of protection, in addition to copyright law, comprised niche markets, pricing, trust, bad publicity, and nontechnical and technical means. 相似文献
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Prof. SUN Changpu from the CAS Institute of Theoretical Physics coworkers from University of Basel in Switzerland have worked out a way - at least in theory - to split a beam of molecules according to their chirality. The technique involves passing the molecules through three different laser beams is similar to the famous Stern-Gerlach effect whereby a beam of atoms passing through a magnetic field is split in two according to the atoms' spin states 《中国科学院院刊(英文版)》2008,22(1):23-23
Prof. SUN Changpu from the CAS Institute of Theoretical Physics and coworkers from University of Basel in Switzerland have worked out a way --at least in theory --to split a beam of molecules according to their chirality. The technique involves passing the molecules through three different laser beams and is similar to the famous Stern-Gerlach effect, whereby a beam of atoms passing through a magnetic field is split in two according to the atoms＇ spin states （Phys. Rev. Lett. 99 130403）. 相似文献
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Milton Mueller 《The Information Society》2001,17(3):151-163
Long-standing conflict between domain name registrants and trademark holders prompted the Internet Corporation for Assigned Names and Numbers (ICANN) to create a global, mandatory arbitration procedure known as the Uniform Dispute Resolution Policy (UDRP). The UDRP has been used in 2166 cases involving 3938 domain names as of 1 November 2000. The policy gives the initiator of a complaint, generally a trademark holder, the right to choose which ICANN-accredited dispute resolution service provider (RSP) will handle the case. During the preparation of the UDRP,some feared that complainant selection would lead to "forum shopping" that might bias the results. This article performs a statistical assessment of the forum-shopping thesis and finds support for it. There are statistically significant differences in the various RSPs' propensity to take away names from defendants; there are also major differences in the number of cases brought to each RSP. RSPs who take away names have the larger share of cases. The study examines other variables that might explain differences in market share, such as price, the plaintiff's nationality, or the time taken to decide a case. It finds that nationality and time also are correlated with market share. The study concludes that shopping for a favorable outcome is an important factor in the UDRP. 相似文献
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Prof. Raymond C.K. Chen a neuropsychologist with the CAS Institute of Psychology has made novel progress in his studies of schizophrenia. His work has been reported by a recent issue of Behavioural Neurology.…… 《中国科学院院刊(英文版)》2008,22(1):15-15
Prof. Raymond C.K. Chen, a neuropsychologist with the CAS Institute of Psychology, has made novel progress in his studies of schizophrenia. His work has been reported by a recent issue of Behavioural Neurology. 相似文献