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31.
AbstractThe potential influence of a developing La Niña on Arctic sea-ice annual variability is investigated using both observational data and an atmospheric general circulation model. It is found that during the developing phase of an eastern Pacific (EP) La Niña event in June, July, and August (JJA) and September, October, and November (SON), the sea-ice concentration (SIC) over the Barents–Kara Seas declines more than 15%. The local atmospheric circulation pattern associated with the EP La Niña is characterized as a weak decrease in geopotential height over the Barents–Kara Seas, combined with an anticyclone in the North Atlantic. The corresponding southerly winds push warm waters northward into the key sea-ice reduction region and directly accelerate sea-ice melt. Meanwhile, the abundant moisture contained in the lower troposphere is transported into the Arctic region by winds resulting from the local barotropic structure. The humid atmosphere contributes to both net shortwave and longwave radiation and thus indirectly accelerates the decline in sea ice. Simulations by the European Centre Hamburg Model, version 5.4, are forced by observed sea surface temperature anomalies associated with EP La Niña events. The results of the simulations capture the North Atlantic anticyclone and reproduce the moisture transport, which supports the premise that an EP La Niña plays a crucial role in sea-ice reduction over the Barents–Kara sector from the perspective of atmospheric circulation and net surface heat flux. 相似文献
32.
ON SOME KEY SEDIMENTATION PROBLEMS OF THREE GORGES PROJECT (TGP) 总被引:1,自引:0,他引:1
Lin Bingnan Dou Guoren Xie Jianheng Dai Dingzhong Chen Jisheng Tang Richang Zhang Ren 《国际泥沙研究》1989,(1)
I. INTRODUCTIONThe Three Gorges Project (TGP) being planned is to be located on the Yangtze River at Sandouplug, 44 km upstream of Yichang (Fig. l). A scheme studied in the feasibility stage has the crest ofthe dam placed at 185 m with a maximums height o… 相似文献
33.
Sun Jinzhong College of Engineering Technology China University of Geosciences Beijing Tan Hanhua Guizhou Institute of Communication Design Guiyang Qi Shengwen Institute of Geology Chinese Academy of Sciences Beijing 《中国地质大学学报(英文版)》2001,12(2)
INTRODUCTIONBecauseofitssimpleoperationandlowcostaswellaseffec tivenessformanyprojects ,heavytampinghasbeenusedwidelyintheworld (Qianetal.,1986 ) .However,thestrongvibrationinsoilmasscausedbyheavytampingmaybeharmfultobuildings,instrumentsandevenhumanbodiesar… 相似文献
34.
有限区域卫星云图资料变分分析的试验研究 总被引:25,自引:6,他引:25
资料分析在数值预报中的重要性受到越来越多的关注,星目前常规探测网的时空局限性,利用分辨率较高的非常规资料势在必行。该文利用一个有限区域中尺度模式MM4,采用变分分析技术对有限区域的常规探空资料和非常规云图资料进行变分分析和数值模拟。 相似文献
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37.
Kinetic study of the hydrocarbon generation from Upper Paleozoic coals in Ordos Basin 总被引:6,自引:0,他引:6
When organic matter during geological processes is affected by a variety of factors such as paleotemperature, and time, complicated chemical reactions will occur, finally resulting in the generation of petroleum and natural gas. These reactions leading to… 相似文献
38.
Fluid inclusion studies of 5 gold deposits connected with alkaline rocks show that quartz separated from auriferous quartz veins contains abundant three-phase CO2-NaCl-H2O inclusions and two-phase CO2-dominated ones,measuring 5-20um in diameter,Homogenization temperatures of the fluid inclusions are mostly within the range of 150-300℃,and the salinities,mainly 0.2wt%-12 wt%(NaCl),Gold mineralizations occurred at depths of 1.4-2.8km,The most striking character of fluid composition is that among the cations,Na^ in dominant,followed by K^ ,Ca^2 ,among the anions,Cl^- is slightly higher than SO4^2-,In the evaporate,H2O is dominant,followed by CO2,The pH values are mainly within the range of 6.5-8.5,indicating that the ore-forming solutions are alkaline in nature.The hydrogen and oxygen isotopic ratios indicate that the ore fluid is composed mainly of magmatic water.With the dropping of temperature in the ore fluid,the contents of CO2 decreased while the salinity increased.The relations between Au and other components of the ore fluid are discussed in the paper,and it is concluded that in these deposits,Chlorides,H2S,SiO2,CO2,etc.in the fluid all are involved in the migration and concentration of Au. 相似文献
39.
西藏改则县托和平错地区展金组中发育一套早—中二叠世以玄武岩类为主、玄武安山岩次之、安山岩少量的海相火山岩组合。该火山岩中玄武岩、玄武安山岩的SiO2含量为44.43%~54.87%,TiO2含量多在4%以上,K2O+Na2O平均为4.57%,玄武岩类富K,玄武安山岩富Na。区内火山岩富集K、Ba、Th、Ta、Ce、P、Zr、Sm、Ti、Cr,亏损Rb、Nb、Hf、Sc,Y/Nb在0.322~0.499之间。综合常量元素和微量元素特征,可将该火山岩归入碱性玄武岩系列。区内火山岩从基性到中性稀土元素总量基本没有变化,REE平均为402.31×10-6,LREE/HREE为8.17~12.69,为轻稀土强烈富集型,δEu为0.93~1.04,平均为0.99,无Eu异常,玄武岩的Th/Ta值多数大于1.6。火山岩的地质特征和地球化学特征表明,本区火山岩产出的大地构造环境为冈瓦纳大陆北缘裂谷环境。 相似文献
40.
华北和印度夏季风降水变化的对比分析 总被引:3,自引:0,他引:3
利用华北和印度夏季降水资料,采用趋势分析、小波变换等方法,对两地区夏季风降水进行了对比分析。结果表明:1) 华北和印度夏季风降水量都存在线性减少倾向,但华北更为显著,减少达16 mm/10 a;2) 华北和印度夏季风降水变化都以18 a周期为主,近年都有逐渐缩短的趋势,而印度的这种周期缩短得比华北更快,近年降水变化周期接近15 a;3) 华北和印度夏季风降水变化在1956、1976、1992/1993年发生了趋势转折;4) 华北和印度降水量主要集中在6-9月,夏季风降水特征非常明显,但两地变化特征表现不尽相同。 相似文献