A comparison between mesospheric wind measurements made near Christchurch (44°S, 173°E) using the high resolution doppler imager (HRDI) and a medium frequency (MF) radar     

D. J. Frame  B. N. Lawrence  G. J. Fraser  M. D. Burrage 《Annales Geophysicae》2000,18(5):555-565

We report on the comparison of winds measured by a medium frequency (MF) radar near Christchurch, New Zealand, and by the high resolution doppler imager (HRDI). Previous comparisons have demonstrated that there can be significant differences in the winds obtained by the two techniques, and our results are no different. However, these data show relatively good agreement in the meridional direction, but large differences in the zonal direction, where the radar is regularly measuring the zonal wind as too easterly. To do the comparison, overpasses from the satellite must be obtained when it is close to the radar site. The radar data are averaged in time around the overpass because we know the radars sample phenomena which have spatial and temporal scales which make them invisible to HRDI. There are a limited number of overpass comparisons which limit our confidence in these results, but a detailed analysis of these data show that the proximity of the overpass is often an important factor in the differences obtained. Other factors examined include the influence of the local time of the overpass, and the amount of radar data averaged around the overpass time.  相似文献   

Letter to the editor A strange cloud in the Arctic summer stratosphere 1998 above Esrange (68°N), Sweden     

J. Siebert  C. Timmis  G. Vaughan  K. H. Fricke 《Annales Geophysicae》2000,18(4):505-509

When the University of Bonn lidar on the Esrange (68°N, 21°E), Sweden, was switched on in the evening of July 18, 1998, a geometrically and optically thin cloud layer was present near 14 km altitude or 400 K potential temperature, where it persisted for two hours. The tropopause altitude was 4 km below the cloud altitude. The cloud particles depolarized the lidar returns, thus must they have been aspherical and hence solid. Atmospheric temperatures near 230 K were approximately 40 K too high to support ice particles at stratospheric water vapour pressures of a few ppmv. The isentropic back trajectory on 400 K showed the air parcels to have stayed clear of active major rocket launch sites. The air parcels at 400 K had travelled from the Aleutians across Canada and the Atlantic Ocean arriving above central Europe and then turned northward to pass over above the lidar station. Parcels at levels at ±25 K from 400 K had come from the pole and joined the 400 K trajectory path above eastern Canada. Apparently the cloud existed in a filament of air with an origin different from those filaments both above and below. Possibly the 400 K level air parcels had carried soot particles from forest wild fires in northern Canada or volcanic ash from the eruption of the Korovin Volcano in the Aleutian Islands.  相似文献   

长江与黄河沉积物中磁铁矿成分标型意义   总被引：22，自引：1，他引：21  

杨守业  李从先  朱金初  张文兰 《地球化学》2000,29(5):480-484

长江与黄河沉积物中磁铁矿的元素组成揭示,两者的ＦｅＯ与Ｆｅ２Ｏ３及一些置换元素的含量差异明显。长江磁铁矿中ＦｅＯ与Ｆｅ２Ｏ３含量稍高于黄河磁铁矿,而Ｔｉ、Ｖ、Ｓｉ、Ａｌ、Ｃｒ、Ｍｇ及Ｍｎ等元素含量明显地低于黄河磁铁矿,元素含量变化显著小于黄河磁铁矿。这反映长江磁铁矿中Ｆｅ＾２＋及Ｆｅ＾３＋的类质同象置换较少,主要为均质相单矿物颗粒,而黄河磁铁矿中元素含量变化大,既有均质相的颗粒,也存在一些Ｆｅ＾２  相似文献   

Mineral and thermal waters of the Ipelská Pahorkatina hillyland     

L. Melioris 《Environmental Geology》2000,39(5):448-462

 Mineral and thermal waters occur at Kalinciakovo, Santovka, Dudince, Slatina and Turovce, in the inner side of the Western Carpathian arc, the south-western margin of the Central Slovak Neovolcanics, and on the so-called Levice spring line. They are important sources of mineral waters for Slovakia, which are used for different purposes (bathing therapy, bottling, recreation). The mineral and thermal waters of Dudince have an extraordinary position among them. The mineral water with its physico-chemical composition and content of gasses enables its wide use for bathing therapy and it occupies a special position among the mineral waters of the Carpathian arc. Received: 9 November 1998 · Accepted: 2 March 1999  相似文献   

Stable isotopic studies of dinosaur eggshells from the Nanxiong Basin, South China   总被引：2，自引：0，他引：2  

ZHAO Zikui  YAN Zheng 《中国科学D辑(英文版)》2000,43(1):84-92

Stable carbon and oxygen isotopes have been observed in dinosaur eggshell samples,identified as Macroolithus yaotunensis,collected in two sections of the Nanxiong Basin,Guangdong Province,South China.Multiple positiveδ18O perturbations that occurred during the K/T transition of about 150 ka suggest that there may have been at least three periods of the extreme dry climate with a mean annual air temperature over 27℃.δ13C ranges from -8.37‰ to -11.60‰ of the dinosaur eggshells,added to the metabolic enrichment of 16‰,may indicate that the dinosaurs represented by this type of eggshells probably consumed the plant species of C3 type with the δ13C values of -24.3‰- -27.6‰.Moreover,the trend toward more negative δ13C values of the eggshells during the K/T transition could be an indirect consequence of a lasting increase in atmospheric CO2 concentration.  相似文献   

Element geochemistry of weathering profile of dolomitite and its implications for the average chemical composition of the upper-continental crust--Case studies from the Xinpu profile,northern Guizhou Province,China     

JI Hongbing  OUYANG Ziyuan  WANG Shijie  ZHOU Dequan 《中国科学D辑(英文版)》2000,43(1)

Geochemical behavior of chemical elements is studied in a dolomitite weathering profile in upland of karst terrain in northern Guizhou.Two stages can be recognized during the process of in situ weathering of dolomitite:the stage of sedentary accumulation of leaching residue of dolomitite and the stage of chemical weathering evolution of sedentary soil.Ni,Cr,Mo,W and Ti are the least mobile elements with reference to Al.The geochemical behavior of REE is similar to that observed in weathering of other types of rocks.Fractionation of REE is noticed during weathering,and the two layers of REE enrichments are thought to result from downward movement of the weathering front in response to changes in the environment.It is considered that the chemistry of the upper part of the profile,which was more intensively weathered,is representative of the mobile components of the upper curst at the time the dolomitite was formed,while the less weathered lower profile is chemically representative of the immobile constitution.Like glacial till and loess,the "insoluble" materials in carbonate rocks originating from chemical sedimentation may also provide valuable information about the average chemical composition of the upper continental crust.  相似文献   

Composition and provenance of the Upper Cretaceous to Eocene sandstones in Central Palawan, Philippines: Constraints on the tectonic development of Palawan     

Shigeyuki Suzuki  Shizuo Takemura  Graciano P. Yumul JR    Sevillo D. David JR    Daniel K. Asiedu 《Island Arc》2000,9(4):611-626

Abstract Sandstones from the Upper Cretaceous to Eocene succession of Central Palawan are rich in quartz grains and acidic volcanic rock fragments. Potassium feldspar grains and granitic rock fragments are commonly observed. The moderate to high SiO₂ and low FeO plus MgO contents of the sandstones support the proposal that clasts were derived from a continental source region. Southern China (Kwangtung and Fukien regions) is inferred to be the source area of the sandstones. The sedimentary facies of the Upper Cretaceous to Eocene succession consist of turbidite and sandstones, suggesting that they were deposited in the deep sea portions of submarine-fans and basin plains situated along a continental margin. These features indicate that the Upper Cretaceous to Eocene succession of the Central Palawan were derived and drifted from the southern margin of China. The tectonic history related to the formation of Palawan Island is also discussed.  相似文献   

南京汤山洞穴石笋稳定同位素指示的气候与环境意义   总被引：16，自引：1，他引：15  

汪永进  许汉奎 《地质学报》2000,74(4):333-338

对南京汤山葫芦洞南壁钙板上一支长８２ｍｍ石笋进行了高精度热电离质谱（ＴＩＭＳ）定年及氧碳同位素分析。结果表明,该支短石笋生长时段长达３００ｋａ左或（距今４６３～１５９ｋａ）,其底部年龄进一步证实南京直立人生存时代早于４５０ｋａＢＰ。δ＾１３Ｃ值在ＭＩＳ６／７界线上的显著漂移揭示了一次土壤侵蚀事件,结束了洞穴文化层的堆积历史。  相似文献   

风化型和含煤建沉积型高岭土的物质组成对比研究   总被引：1，自引：1，他引：0  

魏俊峰 《华东地质学院学报》2000,23(3):184-187

我国高岭土资源丰富,矿床类型多,其中风化和含煤建造沉积型是两类比较重要的高岭土矿床,对这两类高岭土矿床化学组成,矿物组成及高岭石矿物学特征的异同点进行研究和探讨,其结果表明,风化高岭土的化学成分一般属硅高铝低型,钾含量偏高,钛含量低,铁含量则随成矿线岩和风化条件的不同波动范围大,矿物组成主要为结晶度较差的高岭石、水云线和石英,以及极少量的管状埃洛石,含煤建造沉积型高岭土一般属铝高硅低型,钾含量低,钛含量明显偏高,矿物组成简单,高岭石含量〉９５％,结晶度较好。  相似文献   

云南会泽铅锌矿床构造控矿及断裂构造岩稀土元素组成特征   总被引：22，自引：3，他引：19  

韩润生  刘丛强  黄智龙  李元  陈进 《矿物岩石》2000,20(4):11-18

云南会泽超大型铅锌矿床是川滇黔铅锌成矿区大型富铅锌矿床的典型代表,本文在研究矿区成矿地质背景,划分断裂构造岩类型及构造体系的基础上,提出ＮＥ构造带（华夏系）是会泽铅放离主要的成矿构造体系,概括了构造控矿特征,以控矿断裂带中的构造岩、矿及为主要研究对象,分析不同方向断裂的构造岩的稀土元素组成特征,按其特征和酝酿民分模式,将构造岩（矿石）划分为７种类型：Ｅｕ富集－开阔“Ｗ”型、Ｃｅ富集－Ｅｕ弱亏损－平缓型、平缓型、ＨＲＥＥ－ＬＲＥＥ较富集－开阔“Ｖ”字型、Ｅｕ强亏损－下斜型,Ｅｕ亏损－下斜型、Ｅｕ亏损－平缓型、其中ＮＥ向断裂带中的Ｃｅ富集－Ｅｕ弱亏损－平缓型与Ｅｕ富集－平缓型模式的构造岩是成矿预测的微观标志之一。  相似文献