2009年华北大范围暴雪成因及雷达回波特征分析   总被引：1，自引：0，他引：1  

余政  周后福  孙家驰 《山东气象》2011,31(4):12-18

利用石家庄、济南和濮阳多普勒雷达资料,结合天气形势和实况,对2009年11月9—12日华北大范围暴雪天气过程的分析表明:(1)低层冷、中层暖、高层冷的"冷-暖-冷"层结造成了中层以上大气不稳定;中层急流将南方暖湿空气输送到北方,同时低层东北回流将东部海区的水汽向内陆输送,从而为持续性降雪提供了源源不断的水汽;700hPa切变线及低空急流为降水形成提供了触发条件,低空辐合、高空辐散的配置为降水持续提供了动力条件。(2)雷达回波呈现出大范围层状云结构,分布均匀连续,反射率因子一般在15～29dBZ之间;雷达径向速度图上低层零速度线呈"S"型结构,风向随高度顺转,有暖平流存在;2km左右高度存在切变层,低层东北回流把暖湿空气抬升,中层西南气流把暖湿气流源源不断地向华北地区输送。③降水区域与700hPa散度和水汽通量散度中心的叠加区域有较好的对应关系,低空急流和高空急流的加强使回波强度局部加强,达到30～35dBZ,导致局部强降雪的产生。  相似文献   

婺城区地质灾害现状与防治措施     

王铁生 《浙江地质》2013,(7):58-59

金华市婺城区地处浙江省中部偏西,金衢盆地腹部。面积1388平房公里,其中城区面积3404平方公里,人口62万。东邻金东区,南毗武义县,西和西南连龙游县和遂昌县,北接兰溪市,地理坐标：东经119°18′-119°46′,北纬28°44′-29°15′。山区面积占55．16％。丘陵占36．07％,河谷平原占877％,年平均气温17℃左右,多年平均降雨量1640毫米左右。全区森林覆盖率70．2％。  相似文献   

水文现代化评价指标体系研究          下载免费PDF全文

章树安  章雨乾 《水文》2013,33(4):65-69

水文是水利和国民经济建设与发展的重要基础工作之一,是实现水利现代化和实施最严格水资源管理制度的基础与保障。研究水文现代化评价指标体系,对于指导各地开展水文现代化建设具有现实意义。通过对已有的研究成果分析与总结,较全面地阐述了建立水文现代化评价指标思路与原则,应用德尔菲法,确定了10个一级评价指标和53个二级评价指标以及相应的平均权重,从而形成了水文现代化评价指标体系。为我国水文现代化建设评价提供了有一定应用价值的评价指标,对各地稳步推进水文现代化建设具有一定的指导意义。  相似文献   

《西北地质》平均引文率在陕西省排名第四     

《西北地质》2013,(4):141-141

2013年11月27日,在陕西科技期刊学术年会上,中国科学技术信息研究所（简称中信所）著名期刊评价专家张玉华研究员针对陕西省期刊进行了具体统计研究。据最新统计数据显示,陕西省平均引文率前十名的期刊《西北地质》榜上有名。《西北地质》平均引文率在陕西省256种期刊中排名第四。  相似文献   

1960-2004年南京市风速变化及其成因研究     

《青海气象》2014,(1)

利用南京、高淳、江宁、江浦、六合、溧水六个地面站1960—2004年逐日平均风速数据资料,分析了南京市平均风速的时空变化特征及其可能原因。其结果表明:近45年来南京市年平均风速为2.61m/s,最大平均风速出现在3月,为3.08m/s,十月的平均风速最小,为2.45m/s。一年四季中,春季的平均风速最大,为2.93m/s,秋季平均风速最小,为2.50m/s,呈现出"春季大,秋季小"的季节分布类型。近45年间各季节与年平均风速的年代际变化趋势基本一致,都呈现出波动性变化及总体减弱的趋势。在空间上,南京市平均风速呈现出"南大北小"的地理分布格局。风速的变化,主要是由于全球气候变暖下中国乃至亚洲大气环流的变化而引起的局地环流的变化。此外,强冷空气南下次数和强度的减小、台风的减少、观测环境的影响、仪器性能的差异以及统计时次的变更等也是引起南京市风速变化的原因。  相似文献   

Genome-wide survey and analysis of microsatellites in the Pacific oyster genome: abundance,distribution, and potential for marker development     

王家丰  亓海刚  李莉  张国范 《中国海洋湖沼学报》2014,32(1):8-21

Microsatellites are a ubiquitous component of the eukaryote genome and constitute one of the most popular sources of molecular markers for genetic studies. However, no data are currently available regarding microsatellites across the entire genome in oysters, despite their importance to the aquaculture industry. We present the fi rst genome-wide investigation of microsatellites in the Pacifi c oyster Crassostrea gigas by analysis of the complete genome, resequencing, and expression data. The Pacifi c oyster genome is rich in microsatellites. A total of 604 653 repeats were identifi ed, in average of one locus per 815 base pairs(bp). A total of 12 836 genes had coding repeats, and 7 332 were expressed normally, including genes with a wide range of molecular functions. Compared with 20 different species of animals, microsatellites in the oyster genome typically exhibited 1) an intermediate overall frequency; 2) relatively uniform contents of(A)n and(C)n repeats and abundant long(C)n repeats(≥24 bp); 3) large average length of(AG)n repeats; and 4) scarcity of trinucleotide repeats. The microsatellite-fl anking regions exhibited a high degree of polymorphism with a heterozygosity rate of around 2.0%, but there was no correlation between heterozygosity and microsatellite abundance. A total of 19 462 polymorphic microsatellites were discovered, and dinucleotide repeats were the most active, with over 26% of loci found to harbor allelic variations. In all, 7 451 loci with high potential for marker development were identifi ed. Better knowledge of the microsatellites in the oyster genome will provide information for the future design of a wide range of molecular markers and contribute to further advancements in the fi eld of oyster genetics, particularly for molecular-based selection and breeding.  相似文献   

Impact of Meteorological Drought on Streamflow Drought in Jinghe River Basin of China   总被引：1，自引：0，他引：1  

ZHAO Lin  LYU Aifeng  WU Jianjun  Michael HAYES  TANG Zhenghong  HE Bin  LIU Jinghui  LIU Ming 《中国地理科学(英文版)》2014,(6):694-705

Under global climate change, drought has become one of the most serious natural hazards, affecting the ecological environ- ment and human life. Drought can be categorized as meteorological, agricultural, hydrological or socio-economic drought. Among the different categories of drought, hydrological drought, especially streamflow drought, has been given more attention by local govern- ments, researchers and the public in recent years. Identifying the occurrence of streamflow drought and issuing early warning can pro- vide timely information for effective water resources management. In this study, streamflow drought is detected by using the Standard- ized Runoff Index, whereas meteorological drought is detected by the Standardized Precipitation Index. Comparative analyses of fre- quency, magnitude, onset and duration are conducted to identify the impact of meteorological drought on streamflow drought. This study focuses on the Jinghe River Basin in Northwest China, mainly providing the following findings. 1） Eleven meteorological droughts and six streamflow droughts were indicated during 1970 and 1990 after pooling using Inter-event time and volume Criterion method. 2） Streamflow drought in the Jinghe River Basin lagged meteorological drought for about 127 days. 3） The frequency of streamflow drought in Jinghe River Basin was less than meteorological drought. However, the average duration of streamflow drought is longer. 4） The magnitude of streamflow drought is greater than meteorological drought. These results not only play an important theo- retical role in understanding relationships between different drought categories, but also have practical implications for streamflow drought mitigation and regional water resources management.  相似文献   

Improvement of 6–15 Day Precipitation Forecasts Using a Time-Lagged Ensemble Method简     

JIE Weihua  WU Tongwen  WANG Jun  LI Weijing  and LIU Xiangwen 《大气科学进展》2014,31(2):293-304

A time-lagged ensemble method is used to improve 6-15 day precipitation forecasts from the Beijing Climate Center Atmospheric General Circulation Model,version 2.0.1.The approach averages the deterministic predictions of precipitation from the most recent model run and from earlier runs,all at the same forecast valid time.This lagged average forecast （LAF） method assigns equal weight to each ensemble member and produces a forecast by taking the ensemble mean.Our analyses of the Equitable Threat Score,the Hanssen and Kuipers Score,and the frequency bias indicate that the LAF using five members at time-lagged intervals of 6 h improves 6-15 day forecasts of precipitation frequency above 1 mm d-1 and 5 mm d-1 in many regions of China,and is more effective than the LAF method with selection of the time-lagged interval of 12 or 24 h between ensemble members.In particular,significant improvements are seen over regions where the frequencies of rainfall days are higher than about 40％-50％ in the summer season; these regions include northeastern and central to southern China,and the southeastem Tibetan Plateau.  相似文献   

Effects of doubled carbon dioxide on rainfall responses to large-scale forcing: A two-dimensional cloud-resolving modeling study     

LI Xiaofan  SHEN Xinyong  LIU Jia 《大气科学进展》2014,31(3):525-531

ABSTRACT Rainfall responses to doubled atmospheric carbon dioxide concentration were investigated through the analysis of two pairs of two-dimensional cloud-resolving model sensitivity experiments. One pair of experiments simulated pre-summer heavy rainfall over southern China around the summer solstice, whereas the other pair of experiments simulated tropical rainfall around the winter solstice. The analysis of the time and model domain mean heat budget revealed that the enhanced local atmospheric warming was associated with doubled carbon dioxide through the weakened infrared radiative cooling during the summer solstice. The weakened mean pre-summer rainfall corresponded to the weakened mean infrared radiative cooling. Doubled carbon dioxide increased the mean tropical atmospheric warming via the enhanced mean latent heat in correspondence with the strengthened mean infrared radiative cooling during the winter solstice. The enhanced mean tropical rainfall was associated with the increased mean latent heat.  相似文献   

Effects of additional HONO sources on visibility over the North China Plain   总被引：1，自引：1，他引：0  

Ying Li  Junling An  Ismail Gultepe 《大气科学进展》2014,31(5):1221-1232

The objective of the present study was to better understand the impacts of the additional sources of nitrous acid （HONO） on visibility, which is an aspect not considered in current air quality models. Simulations of HONO contributions to visibility over the North China Plain （NCP） during August 2007 using the fully coupled Weather Research and Forecasting/Chemistry （WRF/Chem） model were performed, including three additional HONO sources： （1） the reaction of photo-excited nitrogen dioxide （NO~） with water vapor; （2） the NO2 heterogeneous reaction on aerosol surfaces; and （3） HONO emissions. The model generally reproduced the spatial patterns and diurnal variations of visibility over the NCP well. When the additional HONO sources were included in the simulations, the visibility was occasionally decreased by 20%-30% （3-4 km） in local urban areas of the NCP. Monthly-mean concentrations of NO3, NH＋, SO]- and PM2.5 were increased by 20%-52% （3-11μg m-3）, 10%-38%, 6%-10%, and 6%-11% （9-17 μg m-3）, respectively; and in urban areas, monthly-mean accumulation- mode number concentrations （AMNC） and surface concentrations of aerosols were enhanced by 15%-20% and 10%-20%, respectively. Overall, the results suggest that increases in concentrations of PM2.5, its hydrophilic components, and AMNC, are key factors for visibility degradation. A proposed conceptual model for the impacts of additional HONO sources on visibility also suggests that visibility estimation should consider the heterogeneous reaction on aerosol surfaces and the enhanced atmospheric oxidation capacity due to additional HONO sources, especially in areas with high mass concentrations of NOx and aerosols.  相似文献