2003年淮河流域致洪暴雨的环流演变   总被引：2，自引：6，他引：2  

陈晓红  冯皖平  璩瑛 《气象科学》2006,26(2):192-196

使用EC模式的格点高度场和风场资料,分析2003年6~7月欧亚地区环流形势演变特征与安徽淮河流域致洪暴雨的关系发现:淮河流域的强降雨能持续14 d之久,是500 hPa高空超长波维持2波、长波交替出现5~6波、高纬度为阻塞环流形势以及副热带高压脊长时间稳定在23~27°N偏北位置诸因子共同作用的结果。  相似文献   

A Large-Eddy Simulation and Lagrangian Stochastic Study of Heavy Particle Dispersion in the Convective Boundary Layer   总被引：4，自引：1，他引：4  

Xuhui Cai  Rui Zhang  Yan LI 《Boundary-Layer Meteorology》2006,120(3):413-435

Large-eddy simulation and Lagrangian stochastic dispersion models were used to study heavy particle dispersion in the convective boundary layer (CBL). The effects of various geostrophic winds, particle diameters, and subgrid-scale (SGS) turbulence were investigated. Results showed an obvious depression in the vertical dispersion of heavy particles in the CBL and major vertical stratification in the distribution of particle concentrations, relative to the passive dispersion. Stronger geostrophic winds tended to increase the dispersion of heavy particles in the lower CBL. The SGS turbulence, particularly near the surface, markedly influenced the dispersion of heavy particles in the CBL. For reference, simulations using passive particles were also conducted; these simulation results agreed well with results from previous convective tank experiments and numerical simulations.  相似文献   

2004年鲁西南两次台风低压暴雨过程对比分析     

王友强李春光  王延贵 《河南气象》2006,(1):36-37

对2004年鲁西南两次台风影响造成的大~暴雨过程分析结果表明,西风槽作用下的降水,若有台风低压参与,系统均得以发展,雨势进一步加强。台风低压与西风槽结合及结合点位置,对鲁西南暴雨的形成均很重要。如副高强盛西进时,一般台风低压偏西,与西风槽结合点偏西;副高东退时,结合点一般偏东。  相似文献   

An approximate analytical solution for the deposition of heavy particles released from an elevated line source   总被引：1，自引：1，他引：1  

T. Bouvet  J. D. Wilson 《Boundary-Layer Meteorology》2006,119(1):1-18

This work re-examines and further develops an analytical solution for the deposition swath of heavy particles released in the atmosphere from an elevated source over uniform terrain, correcting the particle diffusivity for the crossing trajectory effect. The revised (approximate) analytical solution proves to be accurate within 20% over a wide range of micrometeorological conditions and particle size, despite its neglect of the turbulence component of the deposition flux. It compares very satisfactorily with experimental data and with the simulations of a Lagrangian stochastic model, provided the variable U(H)/w _g ≤7 (ratio of the mean horizontal wind speed at source height to the particle settling velocity). In this domain of validity, simple formulae relating the statistics of the deposition swath to U(H)/w _g are derived.  相似文献   

Using magnetic susceptibility to find Precambrian impact ejecta: A proposal     

Dallas Abbott  Rajat Mazumder 《Gondwana Research》2007,12(4):571-575

Layers with high magnetic susceptibility contain heavy minerals that are the most likely to preserve signatures of impact in metamorphosed Precambrian rocks. The following impact indicators are resistant to alteration and metamorphism and are likely to be found in heavy mineral layers: impact diamond, SiC, shocked zircon, high-pressure TiO₂ phases, reidite, and high-pressure chromite. Coesite and stishovite could also be present but are not likely to be preserved in rocks metamorphosed above the greenschist facies. Looking for layers with high magnetic susceptibility will also identify layers that might contain concentrations of zircon for dating.  相似文献   

Mineralogy and heavy metal content in sediments from Rio Gato,Carelmapu and Cucao,Southern Chile     

I. González  M. M. Jordán  T. Sanfeliu  M. Quiroz  C. de la Fuente 《Environmental Geology》2007,52(7):1243-1251

In southern Chile, with a mild and rainy climate, high levels of heavy metals have been detected in many gold placer deposits. Many of the contaminants pose risks to human life, and consequently damage the trofic chain in this environment. The study zones selected correspond to the handicraft gold-bearing sands of Rio Gato (Los Muermos), Carelmapu and Cucao. These are all located in the X Region of “Los Lagos” in Chile. The type of methodology used in the characterization of the associated mineralization consists of testing each representative sample with a grain size distribution, statistical parameter analysis and a mineralogical analysis, using a binocular magnifying glass, a petrographic microscope, XRD and SEM/EDX. The chemical composition was defined by means of X ray fluorescence and micro-chemical analysis. The results of the study about sediments in southern Chile are presented. The major concentrations of heavy minerals are generally located in areas of dynamic river energy. In the samples, more than 70% of the heavy minerals were distributed among grain sizes corresponding to thin sand with good grain selection (meshes of 0.25–0.06 mm). The main mineral phases present in the analysed samples were gold, zircon, olivine, ilmenite, hornblende, hypersthene, hematite, garnet, chromite, chlorite, augite, amphibolitic-epidote, etc. The main heavy metals found as a result of the study were mercury, lead, cadmium, chrome, tellurium, indium, zinc, cobalt, copper, platinum, gold, etc., and as well some less common elements like cerium, praseodymium, gadolinium, neodymium, samarium and lanthanum. This research work is only a starting point for carrying out a risk probability mapping of heavy metals and the mineralogy of the Cucao, Carelmapu and Rio Gato gold-bearing sands.  相似文献   

海岸地形作用在青岛一次晚秋暴雨过程中的数值模拟分析          下载免费PDF全文

邰庆国  汤剑平  高留喜  石莹  裴洪芹 《气象科学》2007,27(6):633-640

利用常规资料和卫星、雷达观测,分析了2004年11月9日至10日山东青岛地区一次暴雨的中尺度结构特征,并在初步分析的基础上进行了数值模拟和地形的敏感性对比试验,结果表明:此次暴雨是冷锋前暖区的浅层对流性强降水;西太平洋的水汽是这次暴雨的主要水汽源;模式对这次强降水具有较强的模拟能力;海岸地形作用所产生的次级环流和中尺度重力波,可能是这次对流性强降水的触发机制,同时对这次降水有很大的增幅作用。  相似文献   

南岭山地高速公路雾区恶劣能见度研究   总被引：13，自引：8，他引：13  

吴兑  赵博  邓雪娇  毕雪岩  范绍佳 《高原气象》2007,26(3):649-654

使用2003年10月-2005年3月南岭山地京珠高速公路粤北段云岩雾区路段5套能见度仪的每分钟能见度资料和3套自动气象站的每分钟温度、湿度、风向、风速等气象要素资料, 分析研究了南岭山地高速公路雾区浓雾的能见度特征.结果表明, 南岭山地高速公路雾区各月雾日频率以1月最多, 近一半的天数都有雾; 3月次之, 7月最少.11月到次年5月雾日占全年雾日的80%以上, 形成明显的"雾季".南岭山地高速公路雾区浓雾存在日变化, 雾的频率在一天内凌晨最高, 午后最低, 明显比辐射雾的日变化小, 说明夜间辐射降温虽然不是南岭山地高速公路雾区起雾的主要原因, 但还是起到了一定的加强作用.虽然南岭山地雾区大气中含有丰富的凝结核, 南岭山地形成浓雾还是需要较高的相对湿度, 相对湿度至少要达到91%以上才能形成雾.在雾区出现5.2 m/s的大风时仍然有雾, 有雾时90%以上的风速在3 m/s以下, 有几乎一半的浓雾出现时风速在2 m/s左右, 这与辐射雾形成时大都是静小风的情况形成了鲜明对照.南岭山地高速公路雾区浓雾受地形影响比较大, 迎风坡出现雾的频率比背风坡高.  相似文献   

盐城市发生大暴雨的天气类型分析   总被引：2，自引：2，他引：2  

商兆堂  濮梅娟  蒋名淑 《气象科学》2007,27(4):436-440

按500 hPa形势,盐城市大暴雨的天气类型可划分为台风型和副高边缘型两大类。发生大暴雨时一般副高较强,高空有低槽或切变线,有明显的冷暖气流辐合区。系统深厚,高、中、低层配合较好。地面天气系统主要有冷锋、静止锋、气旋、低压倒槽。  相似文献   

鲁中山区地形对山东省一次暴雨影响的敏感性数值模拟试验   总被引：3，自引：0，他引：3  

张可欣  汤剑平  邰庆国  裴洪芹 《气象科学》2007,27(5):510-514

利用PSU/NCAR MM5V3中尺度数值模式进行了鲁中山区地形对一次台风暴雨的数值模拟敏感性试验,结果分析表明:鲁中山区地形作用对山东省暴雨有重要影响,迎风坡可引起低层气流和水汽的辐合上升运动增强,降水量增加,但偏北气流在迎风坡的水汽辐合不明显,降水量影响不大;山顶引起低层辐合上升运动减弱,辐散下沉运动增强,降水量减小;背风坡引起低层气流和水汽的辐合上升运动增强,降水量增加。  相似文献