首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  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   159篇
  国内免费   2篇
  完全免费   18篇
  大气科学   179篇
  2022年   1篇
  2021年   1篇
  2019年   4篇
  2018年   10篇
  2017年   4篇
  2016年   6篇
  2015年   5篇
  2014年   21篇
  2013年   26篇
  2012年   11篇
  2011年   6篇
  2010年   7篇
  2009年   6篇
  2008年   5篇
  2007年   8篇
  2006年   1篇
  2005年   7篇
  2004年   5篇
  2003年   6篇
  2002年   3篇
  2001年   3篇
  1999年   3篇
  1998年   2篇
  1997年   2篇
  1996年   9篇
  1995年   4篇
  1994年   2篇
  1993年   1篇
  1992年   1篇
  1991年   1篇
  1989年   1篇
  1988年   1篇
  1987年   2篇
  1986年   1篇
  1984年   1篇
  1983年   1篇
  1979年   1篇
排序方式: 共有179条查询结果,搜索用时 874 毫秒
1.
华南中尺度暴雨数值预报的不确定性与集合预报试验   总被引:48,自引:0,他引:48       下载免费PDF全文
陈静  薛纪善  颜宏 《气象学报》2003,61(4):432-446
利用非静力MM5模式,分析了不同积云对流参数化方案对华南暖区暴雨数值预报的不确定性影响,进行了中尺度暴雨模式扰动集合预报试验。不同对流参数化方案的对流凝结加热引起不同的局地温度扰动,通过大气内部的热力动力过程,导致垂直速度的差异,进而影响网格尺度和次网格尺度降水时间、地点和强度。后续降水再通过凝结潜热释放形成新的扰动源。不同积云对流参数化方案还可引起扰动源能量传播方式不同,最终使模拟大气的动力和热力结构有差异。针对物理过程的不确定性,使用两种模式扰动方法构造集合预报扰动模式,第一种方法是随机组合不同积云对流参数化方案和边界层方案,第二种方法是扰动Grell积云对流参数化方案中主要参数振幅。集合预报结果表明,第一种方法的集合预报效果优于第二种方法,仅扰动参数振幅值似乎还不足以反映华南暴雨预报的不确定性。单一的确定性预报在暴雨落区和强度方面的可信度不稳定,集合产品能给华南暴雨过程提供更有用价值的指导预报,具有较高的应用价值。  相似文献
2.
3.
Most studies on the impact of climate change on regional water resources focus on long-term average flows or mean water availability, and they rarely take the effects of altered human water use into account. When analyzing extreme events such as floods and droughts, the assessments are typically confined to smaller areas and case studies. At the same time it is acknowledged that climate change may severely alter the risk of hydrological extremes over large regional scales, and that human water use will put additional pressure on future water resources. In an attempt to bridge these various aspects, this paper presents a first-time continental, integrated analysis of possible impacts of global change (here defined as climate and water use change) on future flood and drought frequencies for the selected study area of Europe. The global integrated water model WaterGAP is evaluated regarding its capability to simulate high and low-flow regimes and is then applied to calculate relative changes in flood and drought frequencies. The results indicate large ‘critical regions’ for which significant changes in flood or drought risks are expected under the proposed global change scenarios. The regions most prone to a rise in flood frequencies are northern to northeastern Europe, while southern and southeastern Europe show significant increases in drought frequencies. In the critical regions, events with an intensity of today's 100-year floods and droughts may recur every 10–50 years by the 2070s. Though interim and preliminary, and despite the inherent uncertainties in the presented approach, the results underpin the importance of developing mitigation and adaptation strategies for global change impacts on a continental scale.  相似文献
4.
Indicators of Climate Change for the Russian Federation   总被引:11,自引:0,他引:11  
Observed climate changes over the Russian Federation (RF) territory are considered. Several indicators based on monthly mean temperature and precipitation station data are used to quantify regional climate changes. Some of these are the components of two aggregated indices of climate change, suggested by Karl et al. (1996): the Climate Extremes Index (CEI) and the Greenhouse Climate Response Index (GCRI). For the RF territory as a whole, and for its western part, the "Russian Permafrost Free (RPF) territory" in particular, changes in surface air temperature are investigated, together with changes in precipitation and drought indices, and also the fraction of the Russian territory experiencing climatic anomalies below and/or above certain specified percentiles. Composite indices CEI-3 and GCRI-3 based on three parameters (air temperature, precipitation and drought indices) are examined, as well as the Climate Anomaly Index (CAI), known in Russia as Bagrov's coefficient of "anomality".It is shown, that over the area of the RPF as a whole, air temperature and the occurrence of drought has increased somewhat during the 20th century, while precipitation has decreased; these changes were non-uniform in space. The linear trend accounts for only a small fraction of the total variability, but the role of climate variations on decadal scales seems more substantial. The CEI, determined as the percentage of the area experiencing extreme anomalies (with a 10% or less frequency of occurrence) of either sign, increased for mean annual temperature, decreased for total precipitation and increased slightly for the occurrence of drought conditions; the aggregated index based on all three of these quantities increased slightly. There was also an increase in the GCRI-3 index, which is indicative of an agreement between the observed climate changes and the changes owing to the greenhouse effect as predicted by climatic models.The observed climate changes are too small to enable us confidently to reject a hypothesis that they are a reflection of the natural variability of climatic parameters within the context of a stationary climate. However, there is no doubt about the reality and importance of the observed changes.  相似文献
5.
干旱及半干旱地区地表能量通量的卫星遥感参数化   总被引:9,自引:0,他引:9       下载免费PDF全文
对干旱及半干旱地区非均匀地表区域地表能量通量的研究是一个十分重要但又是一个难点问题。作者提出了一个基于卫星遥感和地面观测的参数化方案,并把其用于中国西北地区“我国重大气候和天气灾害形成和预测理论的研究”(国家重点基础研究发展规划项目G1998040900,1999-2003)的“敦煌试验”区和“黑河试验”(HEIFE,1989-1994)区,并利用4个景(“敦煌试验区”:2000年6月3日-初夏、2000年8月22日-夏末和2001年1月29日-冬天:“黑河试验”区:1991年7月9日-夏季)的陆地资源卫星Landsat5 TM和Landsat-7 TM资料进行了分析研究,得到了有关干旱及半干旱地区非均匀地表区域地表特征参数、植被参数和地表能量通量的分布图像。最后还讨论了参数化方案的适用范围和需改进之处。  相似文献
6.
Using Remote Sensing to Assess Russian Forest Fire Carbon Emissions   总被引:6,自引:0,他引:6  
Russian boreal forests are subject to frequent wildfires. The resulting combustion of large amounts of biomass not only transforms forest vegetation, but it also creates significant carbon emissions that total, according to some authors, from 35–94 Mt C per year. These carbon emissions from forest fires should be considered an important part of the forest ecosystem carbon balance and a significant influence on atmospheric trace gases. In this paper we discuss a new method to assess forest fire damage. This method is based on using multi-spectral high-resolution satellite images, large-scale aerial photography, and declassified images obtained from the space-borne national security systems. A normalized difference vegetation index (NDVI) difference image was produced from pre- and post-fire satellite images from SPOT/HRVIR and RESURS-O/MSU-E images. A close relationship was found between values of the NDVI difference image and forest damage level. High-resolution satellite data and large-scale aerial-photos were used to calibrate the NDVI-derived forest damage map. The method was used for mapping of forest fire extent and damage and for estimating carbon emissions from burned forest areas.  相似文献
7.
8.
A computational framework to generate daily temperature maps using time-series of publicly available MODIS MOD11A2 product Land Surface Temperature (LST) images (1 km resolution; 8-day composites) is illustrated using temperature measurements from the national network of meteorological stations (159) in Croatia. The input data set contains 57,282 ground measurements of daily temperature for the year 2008. Temperature was modeled as a function of latitude, longitude, distance from the sea, elevation, time, insolation, and the MODIS LST images. The original rasters were first converted to principal components to reduce noise and filter missing pixels in the LST images. The residual were next analyzed for spatio-temporal auto-correlation; sum-metric separable variograms were fitted to account for zonal and geometric space-time anisotropy. The final predictions were generated for time-slices of a 3D space-time cube, constructed in the R environment for statistical computing. The results show that the space-time regression model can explain a significant part of the variation in station-data (84%). MODIS LST 8-day (cloud-free) images are unbiased estimator of the daily temperature, but with relatively low precision (±4.1°C); however their added value is that they systematically improve detection of local changes in land surface temperature due to local meteorological conditions and/or active heat sources (urban areas, land cover classes). The results of 10–fold cross-validation show that use of spatio-temporal regression-kriging and incorporation of time-series of remote sensing images leads to significantly more accurate maps of temperature than if plain spatial techniques were used. The average (global) accuracy of mapping temperature was ±2.4°C. The regression-kriging explained 91% of variability in daily temperatures, compared to 44% for ordinary kriging. Further software advancement—interactive space-time variogram exploration and automated retrieval, resampling and filtering of MODIS images—are anticipated.  相似文献
9.
Summary The energy and water cycle over the Tibetan Plateau play an important role in the Asian monsoon system, which in turn is a major component of both the energy and water cycles of the global climate system. Using field observational data observed from the GAME/Tibet (GEWEX (Global Energy and Water cycle Experiment) Asian Monsoon Experiment on the Tibetan Plateau) and the CAMP/Tibet (CEOP (Coordinated Enhanced Observing Period) Asia-Australia Monsoon Project (CAMP) on the Tibetan Plateau), some results on the local surface energy partitioning (diurnal variation, inter-monthly variation and vertical variation etc.) are presented in this study.The study on the regional surface energy partitioning is of paramount importance over heterogeneous landscape of the Tibetan Plateau and it is also one of the main scientific objectives of the GAME/Tibet and the CAMP/Tibet. Therefore, the regional distributions and their inter-monthly variations of surface heat fluxes (net radiation flux, soil heat flux, sensible heat flux and latent heat flux) are also derived by combining NOAA-14/AVHRR data with field observations. The derived results were validated by using the ground truth, and it shows that the derived regional distributions and their inter-monthly variations of land surface heat fluxes are reasonable by using the method proposed in this study. Further improvement of the method and its applying field were also discussed.  相似文献
10.
The drama of uncertainty   总被引:3,自引:1,他引:2  
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