首页 | 本学科首页   官方微博 | 高级检索  
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   7篇
  国内免费   1篇
  完全免费   2篇
  大气科学   10篇
  2015年   2篇
  2013年   1篇
  2012年   1篇
  2011年   1篇
  2010年   1篇
  2007年   1篇
  2006年   1篇
  2005年   1篇
  2003年   1篇
排序方式: 共有10条查询结果,搜索用时 78 毫秒
Several Holocene loess-soil profiles at the archaeological sites of the political center, and later, the capital cities of the predynastic Zhou and Western Zhou Dynasty (ca. 1400–771 B.C.) inthe southern Loess Plateau were studied multi-disciplinarily. It provides insights into monsoonal climatic change and the relocations of the Zhou culture in this climatically sensitive semiarid zone. Both the analytical data and written records indicate that increased climatic aridity at 1150 B.C. induced a considerable environmental deterioration and degradation of natural resources, especially water shortages, decreases in precipitation and deficits in soil moisture. These resulted in poor harvest and great famines, plagues, domestic upheavals, population migrations, and even conflicts between Zhou people who subsisted on dry farming and nomadic tribes on the northern steppe during the development of the Zhou culture. It seems that persistent droughts forced Zhou people to move from the upland plateau to the lowland riverbanks step by step through relocations, following a direction of increasing climatic humidity, soil moisture, water availability and biodiversity. The southward migration of the nomads on the steppe of the northern Loess Plateau and the Mongolia Plateau in response to the climatic aridity was another dynamic force that caused the relocations of the Zhou culture.  相似文献
青海地区闪电回击通道的温度特性   总被引:3,自引:3,他引:0  
用无狭缝摄谱仪获得了青海高原地区云对地闪电回击过程的光谱,在谱线辨认和光谱特征分析的基础上,根据光谱线相对强度和跃迁参数值,用多谱线法,对回击通道不同高度处的温度进行了定量分析。结果表明,通道温度与闪电放电的强度密切相关,一般情况下,闪电放电过程越强,对应的通道温度越高;对通道不同高度处的数据分析发现,同一回击的通道温度随高度的增加略呈减小趋势。  相似文献
713雷达数据判读与地学可视化   总被引:1,自引:1,他引:0       下载免费PDF全文
713型气象雷达为我国自主设计的固定式测雨雷达,目前我国西北部和中部地区的一些气象局仍在使用。文章简要介绍了713雷达的平面位置显示器(PPI)和距离高度显示器(RHI)两种数据的结构和格式,在充分解析后,采用Visual Basic.NET2005开发语言,完成了对两种雷达回波数据的准确判读。并结合GIS二次开发组件MapX,采用常规天气雷达数据产生回波图像的算法,提出并实现了极坐标系下的雷达平显回波图和高显回波图的地学线型与面型可视化,最大限度恢复了雷达数据中存储的回波信息,为准确分析区域降水提供了依据。  相似文献
Concentrations of peroxy radicals were measured by a chemical amplification technique at a remote forested site as part of the Program for Research on Oxidants in a Forested Region in Nikko (PROFRN). During the measurement period of 22–27 July 2002, the mixing ratios of peroxy radicals averaged for 3 min at midday ranged from 109 to 134 pptv at a height approximately 5 m above the forest canopy. Significant diurnal variation in concentrations of peroxy radicals was observed, with the maximum usually occurring around noon. Most of the variation was driven by changes in the intensity of solar radiation. However, it was found that the peroxy radical concentration reached its peak about 3-h later than that of solar radiation on 24 and 26 July. The origins of this delay are discussed based on an analysis of the total radical budget in that period. A transport of polluted air masses to the site was one of possible causes for the inconsistency. In addition, the measured peroxy radical concentrations were compared with those derived from the deviations of NO-NO2-O3 photo-stationary state (PSSD) for clear days. The estimated half-hour-average concentrations of peroxy radical were in agreement with the PERCA measured in the morning and late afternoon. However the two techniques differed by as much as a factor of two during the time of near midday.  相似文献
During the late sixth century and early seventh century, the Eastern Turkic Empire (i.e., the Eastern Turkic Khanate) was the most powerful country in the Northeast Asia. It collapsed suddenly in a.d. 630, and historians concluded that the combination of social, political and economic factors, as well as the invasion of the Tang Empire, would be the root cause. Here we suggest that a climatic cooling event ca. a.d. 627–629 could be the direct cause. In a.d. 627–629, the Eastern Turkic Empire experienced severe disasters of snow and frost. Many of the sheep and horses died. People suffered great famine and massive deaths. The Empire fell into severe national crisis and collapsed in a.d. 630. Simultaneously, the Tang Empire also experienced three successive years of frost disasters. Climatic cooling possibly also occurred in other regions. Our investigation of the ca. a.d. 627–629 climatic cooling event also improved our understanding of another problem: was the climatic event due to the impact of a ca. a.d. 626 volcanic eruption?  相似文献
王波  霍振华 《大气科学进展》2013,30(4):1213-1223
An extension of the conditional nonlinear optimal parameter perturbation (CNOP-P) method is applied to the parameter optimization of the Common Land Model (CoLM) for the North China Plain with the differential evolution (DE) method. Using National Meteorological Center (NMC) Reanalysis 6-hourly surface flux data and National Center for Environmental Prediction/Department of Energy (NCEP/DOE) Atmospheric Model Intercomparison Project II (AMIP-II) 6-hourly Reanalysis Gaussian Grid data, two experiments (I and II) were designed to investigate the impact of the percentages of sand and clay in the shallow soil in CoLM on its ability to simulate shallow soil moisture. A third experiment (III) was designed to study the shallow soil moisture and latent heat flux simultaneously. In all the three experiments, after the optimization stage, the percentages of sand and clay of the shallow soil were used to predict the shallow soil moisture in the following month. The results show that the optimal parameters can enable CoLM to better simulate shallow soil moisture, with the simulation results of CoLM after the double-parameter optimal experiment being better than the single-parameter optimal experiment in the optimization slot. Furthermore, the optimal parameters were able to significantly improve the prediction results of CoLM at the prediction stage. In addition, whether or not the atmospheric forcing and observational data are accurate can seriously affect the results of optimization, and the more accurate the data are, the more significant the results of optimization may be.  相似文献
 在全球气候变暖背景下,地面接收太阳辐射总量发生改变,探讨自然和人为因素对其影响成为热点。利用线性趋势分析、M-K突变检验和小波分析等方法,分析了1961—2009年大同市地面接收太阳辐射的变化特征,验证地面接收太阳辐射的突变年份和周期变化及未来变化趋势,探讨太阳辐射与相关气象要素的关系。结果表明:近49 a大同市地面接收太阳辐射年平均值为5617.28 MJ/m2,整体呈现明显下降趋势,但2000年后又缓慢上升;大同市地面接收太阳总辐射在1975年发生突变;太阳总辐射的振荡周期为9a,现正处于太阳辐射偏高年份;日照时数逐年递减,地面接收太阳辐射减少,二者呈现显著正相关;降水量在波动中缓慢减少,而地面接收太阳辐射总量减少,二者呈现一定正相关;云量变化逐年减少,但与地面接收太阳辐射相关性不明显,气候的自然因素变化与地面接收太阳辐射的相关性较小。  相似文献
免费师范生专业能力的培养现状是测量免费师范生培养质量的重要指标,也是改革免费师范生教育的事实依据。本研究采用问卷调查法对陕西师范大学的1 531名2008级免费师范生的专业能力进行研究,结果表明:师范生的课堂教学能力和反思发展能力有待提高;不同性别、学科类别的师范生在专业能力上存在差异;艺术生的各项专业能力培养现状均比文科生、理科生要好。为提升师范生专业能力,学校应从注重反思发展、加强教育教学实践、重视专业培养中的群体差异三个方面入手。  相似文献
张菡 《吉林气象》2015,(2):90-93
本文旨在为成人学前教育美术专业的教师改进教学提供借鉴。成人学前教育美术专业教学中存在诸多问题:美术课程设置不够完善、美术师资力量不强、教学资源相对不足、教学内容与方法还不令人满意、学生的自学能力较弱等。针对这种现状,本文拟就所存在的问题作以探讨分析,进而提出相应的改进策略。  相似文献
运用一元回归分析、Mann-Kendall和R/S方法,对1960—2009年汉中市气温、降水量和日照时数变化特征及未来趋势进行分析。结果表明:近50 a来,汉中市年平均气温以0.14℃/10 a的速率升高,并在1997年发生增温突变,其Hurst值为0.94,表明未来气温的变化与过去50 a有较强的持续性,仍将呈现上升趋势。汉中市年降水量以-28.45 mm/10 a的速率显著减少,呈波动变化,突变不显著,其Hurst值为0.75,说明汉中市降水量减少的趋势还将继续;日照时数在过去50 a呈减少趋势,减少率为-56.42 h/10 a,并在1979—1980年发生突变,其Hurst值为0.91,说明汉中市未来日照时数变化趋势与过去一致,仍将持续减少。  相似文献
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号