共查询到20条相似文献，搜索用时 250 毫秒
1.
白洋淀流域年径流变化趋势及气象影响因子分析 总被引：8，自引：0，他引：8
本文以白洋淀流域为研究对象,首先应用Mann-Kendall非参数检验法分析流域内8个典型水文站点近50年的年径流变化趋势。在此基础上采用Hurst指数法分析年径流变化趋势在未来的可持续性。利用Pettitt突变检测法分析各水文站点年径流发生突变的年份,比较突变前和突变后年平均径流量的变化情况。选取流域内和附近6个气象站点1957年-2006年近50年间的年平均气温和年降水量资料,对比其在突变年份前后的变化情况,分析气象要素对流域径流量的可能影响。研究结果表明：白洋淀流域各站点年径流量呈下降趋势且具有较强的持续性,且流域上游年径流下降趋势更为显著,而流域下游年径流下降值β高于上游;1979年是白洋淀流域年径流发生突变的年份,且突变后时段内平均年径流量显著低于突变前时段;对突变前后时期径流变化率的分析表明,沙河水系年径流变化可能主要受气候变化变化影响,而拒马河水系径流变化可能受人类活动影响主导;流域在突变年份以后气温整体升高约1℃,降水量约降低56.6mm,气象因子可能是径流不断减少的重要原因 相似文献
2.
近10 年黑河流域上游积雪时空分布特征及变化趋势 总被引：2，自引：0，他引：2
基于黑河流域上游1960年-2011年降水、气温数据及2000年-2011年MODIS（Moderate-resolution ImagingSpectroradiometer）积雪产品,采用Mann-Kendall非参数检验和累积距平曲线,研究了降水、气温序列的变化趋势和突变点,分析了黑河流域上游积雪面积的年内分布过程和年际变化趋势,探讨了近10a来降水、气温变化对积雪覆盖面积的影响。结果表明：①黑河流域上游年平均气温呈显著的上升趋势,年降水量也呈微弱增加趋势;②黑河流域上游积雪面积年内分布呈双峰型,峰值分别出现在秋季和春季,夏季积雪面积最小;③2000年-2011年积雪面积呈微弱上升趋势,但各季变化不同。春、秋季积雪面积呈上升趋势,夏季为减少趋势,冬季没有明显的变化;④积雪频率有3个高值区,分布在黑河流域上游西岔札马什克水文站周围及以上区域。积雪频率与流域内高程存在显著的相关性;⑤各个季节积雪面积与气温呈负相关的关系;除秋季外,与降水呈正相关的关系。也即较大的降水在较低的气温条件下,有利于积雪的增加,温度的升高则使积雪面积减少。 相似文献
3.
根据日喀则站气象、水文资料对近年来日喀则气候变化趋势、水文要素特征变化进行了初步探讨。分析表明,近41a西藏日喀则站年平均气温表现为明显的升高趋势,温度变化倾向率为0.31/10a,降水呈微弱上升趋势,年波动较大,总体上呈现暖湿化趋势。1956~2003年日喀则站平均流量基本保持不变,与本站降水量有较好的相关性,与上游江孜站降水考虑的情况下两者相关系数高达0.83,说明年楚河流域的影响较大,多年平均径流量为11.93×108m3,6~9月份降水的占全年流量59.6%.近年来年输沙量呈减少趋势,这与流域内水利设施的改善和植被的恢复有很大关系。 相似文献
4.
基于HIMS的黑河上游山区径流模拟分析 总被引：1，自引：0，他引：1
基于HIMS（Hydro-Informatic Modeling System）,构建了黑河上游山区的分布式水文模型,取得了较高的模拟与验证精度,并在不同的气候变化情景下模拟分析黑河上游山区莺落峡水文站径流,结果表明：①HIMS在黑河上游山区具有适应性,日过程模型率定期和验证期Nash-Suttcliffe效率系数均达0.80,月过程模型率定期和验证期均高达0.97;②莺落峡站年径流量与气温呈负相关关系,与降水量呈正相关关系,气温升高和降水量减少都会减少年径流量;③降水不变情景下,气温对不同月份径流量影响不同,气温降低2℃时会加剧径流年内分配不均的程度;而在气温不变的情景下,月径流量均随降水增加而增加,但径流量年内分配格局未受到降水变化的显著影响;④不同气候变化情景下年径流量差异明显,对年径流量最不利的气候变化情景是气温升高2℃,降水减少20%;最有利的情景是气温降低1℃,降水增加20%。 相似文献
5.
黄河上游流域气候变化对径流的影响 总被引：3，自引：0，他引：3
黄河上游是我国重要的水源涵养区。然而,近年来黄河上游年平均气温呈逐年上升趋势,对流域水资源情势造成较大影响。本文基于SWAT模型,研究在未来不同气候情景下,流域径流在未来两个时期（2046年-2065年以及2081年-2100年）的时空分布规律。结果表明,在未来两个时期内,流域径流量呈减少趋势,且2081年-2100年时期的减少幅度较2046年-2065年时期大;流域多年平均径流量、年径流量序列的第10和90百分位值（R10和R90）的最大值与最小值分别出现在CSIRO-A2和INM-B1两种组合情景下;CSIRO模式下流域径流量最大,INM模式下最小,MRI模式居中;日径流量的第90百分位值（Q90）在所有组合情景下都表现出减小的趋势。在不同气候变化情景下,流域未来多年平均径流深的空间分布与基准期较为一致,即上游径流深较大,下游径流深较小;在不同情景下流域多年平均径流深要低于基准期。研究结果可以为黄河流域水资源管理和相关政策的制定提供科学依据。 相似文献
6.
中国黄土高原气候暖干化及其对生态环境的影响 总被引：36，自引：1，他引：36
应用中国黄土高原7省51个代表性气象站1961年～2000年主要气象要素观测资料和1956年～2000年黄土高原中部主要河流的年径流量,采用EOF和其他数理统计方法研究了黄土高原气候和径流量变化特征及其对生态环境的影响,结果表明:中国黄土高原年平均气温呈明显的上升趋势,年平均气温以每年0.026℃/年的速度上升,增温速度大于全国同期增温速度;年降水量和植物生长季降水量均呈递减的趋势,年降水量递减率为-2.095mm/年,递减率高于全国同期值;年平均气温和夏季平均气温变率呈增大趋势;黄土高原中部7条主要河流径流量呈明显的下降趋势,年河流径流量以每年0.4851×108m3/年的速度下降.气候暖干化导致土壤含水量下降,风沙加大,植物存活率降低,植被覆盖率下降,地表土质更趋疏松,是黄土高原区域生态环境趋于恶化的重要原因. 相似文献
7.
黑河流域气候变化的水文水资源效应 总被引：7，自引：0，他引：7
利用4个典型气象站近50年的气温降水资料,分析了黑河流域的气候变化特征。在近50年当中,黑河流域的气候发生了显著的变化,主要表现在气温的升高和降雨量的增加。黑河流域气温的升高十分显著,其升温率远远大于同期北半球的平均升温率,尤其是近几年来增温幅度之大是几十年来所罕见的;降水量的增加虽然没有气温增加那么明显,但总的趋势是增加的。在此基础上,进一步分析了黑河流域气候变化对区域水文水资源的影响,主要表现在:①气候变暖造成了上游山区冰川的不断萎缩和雪线的持续升高,尤其是最近两年间,冰川为较大的负平衡,出现强烈亏损;②由于黑河上游山区夏季降水量的增加和冬春季气温的升高,黑河流域各出山口流量近60年来是趋于增加的,尤以莺落峡水文站最为显著;③在走廊平原区,温度上升造成农业消耗水量的增加,温度每上升1℃,可使水资源消耗量增加2.979×108m3/年左右;④变暖也造成了河湖水质的不断恶化。黑河和下游湖泊水体的矿化度逐年升高。 相似文献
8.
长江上游降水变化及其对径流的影响 总被引：5，自引：0，他引：5
利用长江上游地区60个国家基本、基准站1960年-2009年的月降水量资料和干流区屏山、寸滩和宜昌3个水文控制站同期径流资料,分区域对长江上游地区的降水量、径流量变化趋势以及降水量和径流量的相关性进行了分析.主要结论如下:①年降水量呈上升和下降趋势的气象站点空间分布相对集中,分别分布在屏山站以上流域和屏山站以下流域;屏山站以下流域和整个长江上游地区年降水量近50年呈现下降趋势,屏山站以下流域秋季降水量的显著减少是长江上游年降水量减少的主要原因;②整个长江上游月降水量趋势从1月-7月以上升趋势为主逐渐转变到8月-12月以下降趋势为主,且月降水量变化趋势空间分布有从3月份至9份月由屏山站以下流域开始逐渐向长江源头过渡的趋势,到9月份整个长江上游基本呈减少趋势;③与降水量变化趋势基本一致,屏山站以下流域寸滩和宜昌站年径流下降趋势显著的主要原因是5月-11月径流的减少,且秋季下降显著,而屏山站春、夏、冬和年径流呈上升趋势,且春季和冬季上升趋势很显著;④整个上游地区面雨量与径流量具有很好的相关性,同期面雨量与径流量在月、季和年尺度上相关性都较显著.屏山以上流域隔月相关比同期相关性强. 相似文献
9.
选取贡嘎气象站1981-2010年平均气温、降水量序列,分析表明:贡嘎县年平均气温8.6℃,年平均最高气温16.4℃,年平均最低气温2.0℃,最热月平均最高气温23.8℃,最冷月平均最低气温-8.7℃,贡嘎站年平均气温呈明显的上升趋势,并且以0.32℃/10a的速率上升。贡嘎县年降水量392.1mm,其中8月最多,为120.6mm,1月最少,为0.3 mm,夏季降水量292.6mm,月站年降水量的74.6%,冬季降水量仅1.5mm,约占年降水量的0.4%,近30年的年降水量成增加趋势,但增幅仅为3.93mm/10a。 相似文献
10.
气候变化和人类活动对湟水河流域径流量影响的定量评估 总被引：7，自引：0，他引：7
湟水河是西北干旱区重要河流之一,对维持西北干旱区生态平衡具有极其重要的作用。近年来,湟水河流域水资源减少已经引起了严重的生态环境问题,本文根据流域内1966-2010年水文气象数据,采用累积距平法、累积量斜率变化率法,对湟水河流域径流量和气候变化特征及趋势进行了分析,并定量评估了气候变化和人类活动对径流量变化的影响。结果表明:年降水量、蒸散发量和径流量总体均呈减少趋势;径流量的下降变幅为0.1亿m3/10a,具有4a、9a和20a的准周期变化,且在1987年前后发生了突变;气候变化对湟水河流域径流减少的贡献率达35.46%,人类活动改变了部分水循环的路径,对径流的减少起主导作用,贡献率为64.54%。 相似文献
11.
A research group led by Prof. ZHAI Qiwei from the Institute for Nutritional Sciences under the CAS Shanghai Institutes for Biological Sciences has discovered that even relatively low doses of resveratrol-a chemical found in the skins of red grapes in red wine-can improve the sensitivity of mice to the hormone insulin according to a report in the October issue of Cell Metabolism.…… 《中国科学院院刊(英文版)》2008,22(1):14-15
Aresearch group led by Prof. ZHAI Qiwei from the Institute for Nutritional Sciences under the CAS Shanghai Institutes for Biological Sciences has discovered that even relatively low doses of resveratrol--a chemical found in the skins of red grapes and in red wine--can improve the sensitivity of mice to the hormone insulin, according to a report in the October,2007 issue of Cell Metabolism. As insulin resistance is often characterized as the most critical factor contributing to the development of Type 2 diabetes, the findings“provide a potential new therapeutic approach for preventing or treating” both conditions, the researchers said. 相似文献
12.
《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
13.
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
14.
《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
15.
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
16.
Active biological molecules functional structures can be fabricated into a bio-mimetic system by using molecular assembly method. Such materials can be used for the drug delivery disease diagnosis therapy new nanodevice construction.…… 《中国科学院院刊(英文版)》2008,22(1):22-22
Active biological molecules and functional structures can be fabricated into a bio-mimetic system by using molecular assembly method. Such materials can be used for the drug delivery, disease diagnosis and therapy, and new nanodevice construction. 相似文献
17.
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
18.
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
19.
Leah A. Lievrouw 《The Information Society》2000,16(2):155-159
This essay focuses on universal service and the Internet as means to support social and political participation. The emphasis on access to telecommunications systems in conventional approaches to universal service is contrasted with access to content. A model of the information environment is described that accounts for the roles of content and conduit, both of which are necessary conditions to achieve true access. A method is outlined for employing information indicators to observe or measure the information environment. 相似文献
20.
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