川西高原持续性暴雨特征和水汽输送     

武敬峰  徐晓芳  赵巍燃  青泉  邹玲 《气象科技》2020,48(5):704-716

利用常规资料、NCEP FNL分析资料和HYSPLIT模式,对2008—2017年川西高原持续性暴雨过程的时空分布、环流分型、水汽源地和输送路径进行分析。结果表明:①2008—2017年川西高原单站持续性暴雨的总频次为337次,在21次区域持续性暴雨中,位于高原与盆地过渡区的泸定、康定、汶川出现持续性暴雨次数最多;②7月发生频率最高,持续时间多为3～4天;③将影响川西高原暴雨的环流分型为两槽一脊型、一脊一槽型、西风槽型和偏西气流型,其中孟加拉湾气旋影响有16例,6—7月个例都有孟加拉湾气旋的存在;④川西高原上空气团主要通过4条路径进入,源自北大西洋、地中海和伊朗中北部的西北路径占比29%,源自里海到咸海之间地区的东北路径占比17%,源自热带印度洋洋面的西南和东南路径各占比43%和11%,偏北路径的空气质点起始高度比偏南路径的高,相应的温度和水汽含量也偏低;⑤将水汽输送分为"S"型、偏西气流型和偏南气流型3个类型。  相似文献   

实现基于JDO的电子政务系统持久层     

董樵  苗放  祖彩霞 《物探化探计算技术》2004,26(2):189-192

JDO为对象持久性提供了第一个标准化的、完全面向对象的方法。JDO不但实现了透明的对象存储，而且提供到任何数据底层的存储功能，使得应用可移植性更强。完备的数据存储功能，易于维护的程序代码及开放的规范标准，都使JDO成为一种优秀的对象持久性机制。  相似文献   

Fractal Analysis of the Gray-Scale Intensity Data of Finely Laminated Sediments from Bainbridge Crater Lake, Galápagos     

N. A. Bryksina  W. M. Last 《Mathematical Geology》2005,37(4):327-336

The gray-scale intensity data of finely laminated sediments from Bainbridge Crater Lake, Galápagos, were analyzed in terms of Hurst exponent and fractal dimension. The sediment record preserved in this volcanic maar provides a continuous history of past El Niño/Southern Oscillation (ENSO) events over the last 6200 years. Accelerator mass spectrometry radiocarbon data show that sedimentation rate was not constant for whole core. To take into consideration this fact gray-scale intensity data from analyses of X-radiography images of a 4.1 m long core from this basin were divided into Data 1 and Data 2. Data 1 corresponds to the more recent part of stratigraphic sequence, which was deposited since 3000 yr BP; Data 2 is from the earlier part of record between 6200 and 3000 yr BP. A persistent behavior with a Hurst exponent of H = 0.88 and H = 0.8 was found by power spectrum analysis method for Data 1 and Data 2, respectively. The width method of analysis shows that ENSO fluctuation before 3000 yr BP had a persistent behavior on a time-scale up to 26 years, while the more recent El Niño occurrences have a persistent behavior on a time-scale up to 5.6 years.  相似文献   

夏季欧亚中高纬持续流型特征Ⅰ:流型指数与持续流型   总被引：8，自引：1，他引：8       下载免费PDF全文

潘婕  王盘兴  纪立人 《气象科学》2004,24(2):127-136

定义了夏季(6～8月)欧亚中高纬500hPa逐日流型指数Ⅰ，用它确定了1959～2000年夏季欧亚中高纬典型持续流型W、E、C。统计表明，流型指数Ⅰ、持续流型与欧亚中高纬500 hPa环流形势特征及我国东部夏季降水异常关系密切，从而证明了它们的合理性和应用价值。  相似文献   

夏季北半球500 hPa位势高度场持续性异常的地理分布及区域特征   总被引：10，自引：3，他引：10  

李金龙  纪立人 《大气科学》1994,18(2):163-172

本文利用２３年夏季3个月的５００ hPa位势高度场，对２０°Ｎ以北的热带以外地区的位势高度异常进行了分析，着重研究了持续时间超过天气尺度扰动时间（大约1周）的持续异常。结果表明:５００ hPa高度场上持续异常的产生?具有很大的地理依赖性，在以下几个地区最容易产生持续异常:（１）北太平洋中东部到阿拉斯加南部（ＮＥＰ）。（２）北大西洋东部到欧洲大陆西海?岸（ＥＡＴ）。（３）前苏联西北部的新地岛附近（ＷＮＳU）。（４）加拿大北部的哈得逊湾附近（ＮＣＡ）。（５）白令海峡以北的北冰洋地区（ＡＲＣ）。进一步对异常关键区统计分析得到:异常多发区特征显著地不同于异常少发区，正异常与负异常也有所差别。  相似文献   

Sediment records of persistent organic pollutants （POPs） in relation to regional economic development： A comparison study in both Pearl River Delta and Yangtze River Delta, China     

Gan ZHANG Lingli GUO Guoqing LIU Jun LI Zhangdong JIN Shihua QI Xiangdong LI 《中国地球化学学报》2006,25(B08):188-189

Persistent organic pollutants （POPs） are semi-volatile chemicals that are toxic to wildlife and human. Typical POPs include most organochlorine pesticides （OCPs）, polycyclic aromatic hydrocarbons （PAHs）, polychlorobiphenyls （PCBs）, polybrominated biphenyl ethers （PBDEs）, etc. Most POPs are hydrophobic, capable of accumulating and existing for a long time in the sediments. Well preserved, laminated sediment layers hence can serve as archives for POP pollution history in the sediment pool. Rapid economic growth has taken place since the early 1980s in most parts of China, of which the Yangtze River Delta, the Pearl River Delta and the Pan-Bohai Bay took the lead. Along with the brilliant regional economic development, the environmental quality has been severely deteriorated. For a more sustainable economic and social development, it is of vital need to understand the relationship between regional economic development and environmental pollution.  相似文献   

西北太平洋冷海温对东亚初夏大气环流影响的数值研究   总被引：1，自引：1，他引：1       下载免费PDF全文

袁佳双  郑庆林 《应用气象学报》2006,17(3):310-315

利用改进的NCAR CCM3气候模式, 研究了1992年西北太平洋持续冷海温对东亚初夏季节大气环流的影响。西北太平洋冷海温不利于初夏东亚南支西风急流季节性北移, 引起亚洲东部沿海低槽明显加深, 东亚大槽平均高度场降低了4.66 dagpm, 从而也不利于西太平洋副热带高压的西伸加强。西北太平洋冷海温还不利于我国大陆初夏温度场回升, 特别是引起我国东北地区近地面温度下降2~5 ℃, 是影响东北冷夏现象的重要原因之一。模拟结果表明, 1992年初夏江淮入梅期较常年偏晚, 降水异常偏少, 与紧邻东亚大陆的西北太平洋持续冷海温有关。  相似文献   

Gas segregation in dykes and sills     

Thierry Menand  Jeremy C. Phillips 《Journal of Volcanology and Geothermal Research》2007

Many basaltic volcanoes emit a substantial amount of gas over long periods of time while erupting relatively little degassed lava, implying that gas segregation must have occurred in the magmatic system. The geometry and degree of connectivity of the plumbing system of a volcano control the movement of magma in that system and could therefore provide an important control on gas segregation in basaltic magmas. We investigate gas segregation by means of analogue experiments and analytical modelling in a simple geometry consisting of a vertical conduit connected to a horizontal intrusion. In the experiments, degassing is simulated by electrolysis, producing micrometric bubbles in viscous mixtures of water and golden syrup. The presence of exsolved bubbles induces a buoyancy-driven exchange flow between the conduit and the intrusion that leads to gas segregation. Bubbles segregate from the fluid by rising and accumulating as foam at the top of the intrusion, coupled with the accumulation of denser degassed fluid at the base of the intrusion. Steady-state influx of bubbly fluid from the conduit into the intrusion is balanced by outward flux of lighter foam and denser degassed fluid. The length and time scales of this gas segregation are controlled by the rise of bubbles in the horizontal intrusion. Comparison of the gas segregation time scale with that of the cooling and solidification of the intrusion suggests that gas segregation is more efficient in sills (intrusions in a horizontal plane with typical width:length aspect ratio 1:100) than in horizontally-propagating dykes (intrusions in a vertical plane with typical aspect ratio 1:1000), and that this process could be efficient in intermediate as well as basaltic magmas. Our investigation shows that non-vertical elements of the plumbing systems act as strong gas segregators. Gas segregation has also implications for the generation of gas-rich and gas-poor magmas at persistently active basaltic volcanoes. For low magma supply rates, very efficient gas segregation is expected, which induces episodic degassing activity that erupts relatively gas-poor magmas. For higher magma supply rates, gas segregation is expected to be less effective, which leads to stronger explosions that erupt gas-rich as well as gas-poor magmas. These general physical principles can be applied to Stromboli volcano and are shown to be consistent with independent field data. Gas segregation at Stromboli is thought likely to occur in a shallow reservoir of sill-like geometry at 3.5 km depth with exsolved gas bubbles 0.1–1 mm in diameter. Transition between eruptions of gas-poor, high crystallinity magmas and violent explosions that erupt gas-rich, low crystallinity magmas are calculated to occur at a critical magma supply rate of 0.1–1 m³ s^− 1.  相似文献   

大气河对2013年“7.9”四川盆地持续性暴雨作用的诊断分析     

岳俊  李国平 《成都信息工程学院学报》2015,30(1):72-80

2013年7月7~11日,四川盆地大部分地区出现了持续性强降雨天气(以下简称四川"7.9"暴雨)。此次过程的降水中心稳定少动、降水强度及总量大、持续时间长,累积降水量最高达到了1000mm以上,造成严重灾害。为分析位于孟加拉湾地区的大气河对四川"7.9"暴雨的影响。利用NCEP/NCAR再分析资料,通过研究孟加拉湾大气河水汽对这次暴雨的作用及影响,得到的结果表明:此次持续性暴雨过程中,孟加拉湾大气河受西太平洋副高东撤影响,并在200 h Pa和850 h Pa高低空急流的共同作用下,不断向四川地区输送水汽。这种水汽输送一直持续到11日才停止,此时降水也趋于结束。在整个暴雨过程中,850 h Pa上孟加拉湾大气河输送的水汽由于云贵高原阻挡,而绕开云贵高原在南海地区与西太副高外围的水汽以及南半球的越赤道气流汇合后,在低空急流左侧辐合气流作用下输送到四川盆地,为暴雨产生提供水汽。同时,700 h Pa上的水汽直接越过云贵高原到达四川盆地。孟加拉湾大气河的这两种输送方式为四川盆地持续性暴雨提供了充足的水汽供应。  相似文献   

GFS对我国南方两次持续性降水过程的预报技巧评估   总被引：2，自引：1，他引：1  

董颜  刘寿东  王东海  赵艳风 《气象》2015,41(1):45-51

采用美国全球预报系统（Global Forecasting System,GFS）资料,利用谐波滤波提取空间长波、超长波分量,检验评估了GFS对2012年7月11—31日东亚地区大气环流场和降水的可预报能力。结果表明：GFS模式对东亚地区的中低层高度场预报可靠时效维持6 d以上,高层预报可靠时效可达10 d;长波、超长波的可预报效果显著,其中高度场长波5～8波的预报效果好于3～6波,风场则相反;GFS对我国南方两次持续性降水过程的可预报天数维持在8 d左右,并可提前2天预报出强降水带位置;模式对持续性降水过程预报相对站点观测降水量整体偏强。  相似文献