中高层大气瞬态发光事件（TLEs）及可能的影响   总被引：1，自引：0，他引：1  

郄秀书  吕达仁  卞建春  杨静 《地球科学进展》2009,24(3):286-296

中高层大气瞬态发光事件（TLEs）是发生于活跃雷暴上空平流层和中间层的一类快速大气放电现象。根据光辐射的形态特征和发生位置的不同,可将已发现的TLEs归纳为4类：由电离层快速向下发展的Red Sprites(又称红色精灵,红闪);由雷暴云顶部向上发展的Blue Jets（又称蓝色喷流,蓝激流）;由闪电激发的低电离层区域的圆环状放电ELVEs(Emissions of Light and VLF perturbation due to EMP Sources,又称光辐射和EMP源引起的甚低频扰动) 和由云顶向电离层快速向上发展的Gigantic Jets(又称巨大喷流)。对已有的TLEs现象学和形态特征的观测事实以及物理机制和理论研究等进行了回顾,讨论了TLEs对平流层和中间层大气以及电离层的可能影响,并提出了目前在TLEs理论方面尚未解决的问题,指出了进一步观测和理论研究的必要性。  相似文献   

晚中生代地球表层重大地质事件的陆地环境剧变与生物群演替响应   总被引：3，自引：1，他引：2       下载免费PDF全文

柳永清  旷红伟  姬书安  吕君昌  刘燕学  江小均  彭楠  陈铭培  李家华 《地学前缘》2009,16(5)

晚中生代时期华北东北部发育燕辽生物群、热河生物群和阜新生物群陆地生物群。它们的快速演变过程和华北克拉通上同时期发育的岩石圈减薄、大面积强烈岩浆活动、变质核杂岩及伴随的伸展盆地等地球表层重大地质事件并行发生,表现着地壳表层系统圈层间的相互作用和响应。生物群的繁盛与灭绝与地球表层大规模岩浆-火山活动(髫髻山组—张家口组和大北沟组—义县组)发育时代高度协同一致。地球表层重大地质事件直接或间接地控制或改造着地球表层古地理和古生态环境,生物群只得调整自身去适应环境和生态背景的改变。火山-岩浆活动改变着地质-生态环境,生物群都紧密联系多期次火山-岩浆活动,化石也都被埋葬在沉积-火山碎屑岩中。华北克拉通破坏重大地质事件发生响应于全球变化和统一地球表层系统。盆地沉积充填序列、特殊陆相环境沉积建造、特殊环境沉积物等记录了响应的古地理、古环境变化与响应。陆地生物群分布、演化、更替与精确定年,脊椎-无脊椎生物(化石)埋葬特征,生物演化速率、消长关系和生物群(组合)更替的形式和性质,以及脊椎动物骨骼、牙齿的常量、微量元素、H-B-C-N-O-S和C-O-Sr等地球化学特征的研究可以恢复和重建古地理、古生态环境和古生态系统。  相似文献   

松辽盆地白垩系青山口阶缺氧事件层的有机地球化学特征   总被引：1，自引：0，他引：1       下载免费PDF全文

孔惠  黄永建  黄清华  张文婧  谢磊  刘学红  谢晓云 《地学前缘》2009,16(6):96

松辽盆地白垩系青山口阶下部广泛分布一套富含有机碳的黑色泥岩、页岩沉积,它具有干酪根碳同位素正偏、重排甾烷含量低,普遍存在伽马蜡烷生物标志化合物等有机地球化学特征,代表了白垩纪温室效应时间窗内古湖泊贫氧环境条件下的沉积产物。结合生物地层研究成果,认为青山口阶下部曾发生过古湖泊缺氧事件,其层位大体可与白垩纪古海洋Cenomanian-Turonian界线事件层进行对比,由此提出了松辽盆地青山口阶下部的时代归属于晚白垩世Cenomanian晚期—Turonian早期的新观点。  相似文献   

SRES A2情景下中国气候未来变化的多模式集合预测结果   总被引：56，自引：3，他引：53       下载免费PDF全文

姜大膀  王会军  郎咸梅 《地球物理学报》2004,47(5):776-784

采用政府间气候变化委员会资料中心的模式预测结果,本文分析了SRES A2温室气体和气溶胶排放情景下中国大陆21世纪前30年的10年际气候变化趋势. 研究揭示：大陆冬季和夏季表面温度、表面最高温度和最低温度分别升高0.3～2.3℃、0.1～2.0℃、0.5～2.7℃,增幅大体上呈现东西向带状分布,由南至北升温逐渐加强,且增幅随时间加大. 此外,上述三气候要素冬季升温幅度要大于同期夏季、表面最低温度升幅要强于同期表面最高温度,冬季和夏季表面温度的季节内变化范围减小. 冬季东亚地区海平面气压异常幅度在-1.0hPa至0.4hPa之间变化,呈东西向带状分布,表现为南正北负、随时间推进异常幅度有所加大,正负交界面向南扩展;同时,东北、华北和西部海平面气压负异常较大. 夏季海平面气压异常空间分布与冬季相似. 2001～2030年,青藏高原大部、大陆东南部和河套大部分地区降水量增加0.1～0.8mm/d.  相似文献   

2001年3月2日磁通量传输事件特性的研究   总被引：3，自引：1，他引：2       下载免费PDF全文

左平兵  刘绍亮  金曙平  刘振兴  史建魁 《地球物理学报》2004,47(3):376-384

2001年3月2日11:00 至11:15 UT 期间,Cluster Ⅱ在南半球极尖区晨侧附近磁鞘内探测到3个通量传输事件（简称FTEs）. 本文利用Cluster Ⅱ星簇4颗卫星观测到的磁场和等离子体资料研究了这些通量传输事件的磁场形态和粒子特征. 并利用它们探测到的空间磁场梯度资料由安培定律直接求出星簇所在区域的电流分布. 结果指出：（1）BY占优势的行星际磁场结构在磁层顶的重联可以在极尖区附近发生;（2）FTEs通量管形成初期内外总压差和磁箍缩应力不一定平衡,达到平衡有一发展过程;（3）FTEs通量管截面在L M平面内的线度约为1.89RE;（4）FTEs通量管中等离子体主要沿轴向场方向流动,整个通量管以慢于背景等离子体的速度沿磁层顶向南向尾运动;（5）FTEs通量管中不仅有轴向电流,也存在环向电流. 轴向电流基本沿轴向磁场方向流动. 轴向和环向电流在管内均呈体分布,因而轴向电流产生的环向磁场接近管心时不断减小到零,而环向电流生成的轴向场则不断增大到极值;（6）在通量管的磁鞘部分观测到磁层能量粒子流量的增强,这表明通量管通过磁层顶将磁鞘和磁层内部连通起来了.  相似文献   

A Hall MHD model to study energetic charged particle events produced during fluctuations in the interplanetary magnetic field intensity     

F.C. Huang  Z.W. Ma  Z.M. Sheng   《Planetary and Space Science》2008,56(7):913-916

Energetic charged particles, which are often observed in solar active regions, may be also produced in interplanetary space due to the decoupling of ions and electrons in plasma. The Hall term in general Ohm's law is generally thought to be responsible for the decoupling of electrons and ions in plasma during magnetic reconnection. In this paper, a Hall MHD model is developed to study energetic charged particle events produced during fluctuations in the interplanetary magnetic field intensity. Two energetic charged particle events are used to test this model. It is concluded that the Hall effect does not only play the important role in the process of magnetic reconnection, but also in energetic charged particle events produced during fluctuations in the interplanetary magnetic field intensity.  相似文献   

Seismicity and seismotectonics of West Saxony, Germany — new insights from recent seismicity observed with the Saxonian seismic network     

M. Korn  S. Funke  S. Wendt 《Studia Geophysica et Geodaetica》2008,52(4):479-492

A new network of permanently recording seismic stations in West Saxony has considerably improved detection threshold, location accuracy and depth determination in this seismically active region. Between 2001 and 2007 more than 900 events have been located. Seismicity mainly occurred along a band stretching north-south between Leipzig and Vogtland/NW Bohemia area with local magnitudes ranging between −0.8 and 2.8. Seismicity clearly delineates the Leipzig-Regensburg (L-R) fault zone striking N-S, and the Gera-Jachymov (G-J) fault zone striking roughly NNW-SSE. The hypocentral depths can be divided into two depth ranges, one at depths below 10 km, and a second at less than 10 km depth that only extends S-N from the Vogtland until the crossing between L-R and G-J fault zones. A small earthquake sequence that occurred near Werdau/Zwickau in August 2006 at almost the same epicenters as an earlier sequence 1997/98 seems to confirm this finding: a relative localization of 15 events with the double-difference technique clearly reveals two distinct subclusters at about 6 and 12–14 km depth. With the improved station coverage 33 new fault plane solutions from events along the L-R fault zone north of the swarmquake area could be determined from P-polarities and P/S ratios. They do not differ significantly from solutions in the Vogtland/NW-Bohemia area and are mostly compatible with a N-S oriented fault plane. Strike slip mechanisms with or without a dip slip component dominate.  相似文献   

Seasonal and inter-annual zooplankton dynamics in temporary pools with different hydroperiods   总被引：1，自引：0，他引：1  

Silvia Tavernini   《Limnologica》2008,38(1):63-75

The results of a research carried out in 2001 on nine temporary mountain pools (Northern Apennines, Italy) underlined a major role of hydroperiod in shaping zooplankton communities of temporary habitats. In 2002, the same pools were studied to assess inter-annual differences in zooplankton seasonal patterns. Data on precipitations (both snow and rainfalls) were collected to evaluate the influence of precipitation regimes on hydroperiod and concurrently on hydrochemical features and zooplankton dynamics.Mean annual snow and rainfall abundances were highly similar in both years but precipitation patterns were different. Moreover, different air temperatures were measured in the 2 years of study. These factors influenced water persistence and dry and wet cycles in the pools: in 2001, three pools dried out in summer and remained dry until autumn rainfalls (type A pools), in five pools (type B pools) the summer dry period was interrupted by re-filling due to storms in July and only in one pool water did remain for the entire research period (C1). In 2002, type A and B pools underwent only one dry phase (June–July) while C1 showed a hydroperiod similar to the one that occurred in the previous year. Overall, type A and B pools can be classified as ‘seasonal’ and C1 as ‘near-permanent or permanent’.Principal component analysis and paired t-tests did not show significant differences between years in the hydrochemical features of the pools. However, the seasonal pools showed a wide range of variation in their hydrochemical parameters while water features of the permanent pool presented less variability.Within the pools, divergences in the number and in the type of zooplankton taxa between the 2 years were limited. Rotifer and copepod density of the seasonal pools were comparable over years and only cladocerans exhibited distinct density dynamics. Cladoceran appeared to be associated with ionic content and influenced by the occurrence of ice-melting and by the wet phase length of the pools.On the contrary, the permanent pool showed diverse zooplankton seasonal patterns in 2001 compared to 2002. Over years, different pH values were measured; pH and conductivity varied with changing water volume, which in turn explained a significant amount of the observed variation in zooplankton densities in 2002.  相似文献   

Possible role of fluid overpressure in the generation of earthquake swarms in active tectonic areas: The case of the Peloritani Mts. (Sicily,Italy)   总被引：1，自引：0，他引：1  

S. Giammanco  M. Palano  A. Scaltrito  L. Scarfì  F. Sortino 《Journal of Volcanology and Geothermal Research》2008

The Peloritani Mts. (NE Sicily) are characterized by frequent seismicity. Between 1994 and 2006 more than 1000 earthquakes (1.0 ≤ M_L ≤ 3.3) occurred, mostly as highly clustered swarms located at shallow depth near the villages of Castroreale and Rodì Milici (western part of Peloritani Mts.). The same area is also characterized by some geothermal springs and gas vents. Using a multidisciplinary approach, data were collected on the tectonic setting, seismicity pattern and geochemical characteristics of fluid emissions, with the aim of understanding the process of earthquake swarm generation beneath the investigated area.  相似文献   

义乌市降水变化特征分析          下载免费PDF全文

冯利华  赵贤产  毛樟林  华云峰  朱跃娟  朱持则  张行才  骆高远 《气象与环境学报》2008,24(1):1-4

根据历史和实测资料的统计分析,得到义乌市的降水变化特征。结果表明:丰水期义乌市的涝年偏多,旱年偏少,而枯水期则旱年偏多,涝年偏少。厄尔尼诺事件的当年或翌年,义乌市的降水显著偏多,而拉尼娜事件的当年或翌年,义乌市的降水则显著偏少。丰水期平均入梅日偏早,平均出梅日偏晚,平均梅雨日数偏长,平均梅雨量偏多,而在枯水期则反之。义乌市6月6—15日入梅的可能性最大,出梅日期的时间分布相对比较分散,其集中期的发生规律不如入梅集中期明显。厄尔尼诺事件的当年或翌年,义乌市的出梅日偏晚,而拉尼娜事件的当年或翌年,义乌市的出梅日偏早。研究结果可为水库源区雨季的人工增雨作业提供科学依据。  相似文献