Conversion characteristics between barotropic and baroclinic circulations of the sah in its seasonal evolution

In the context of 1958-1997 NCEP/NCAR re-analyses, the South Asia high (SAH) was divided into two components, barotropic and baroclinic, the former based on mass weighed vertical integration and the latter on the difference between the measured circulation and the barotropic component counterpart, where upon the barotropic and baroclinic circulation conversion features were addressed of the research SAH during its seasonal variation. Evidence suggests that i) in summer (winter), the SAH is a thermal (dynamical) system, with dominant baroclinicity (barotropicity), either of the components accounting for approximately 70% of the total contribution; ii) as time progresses from winter to summer, accompanied by the barotropic SAH evolving into its baroclinic analog, the SAH is moving under the “thermal guidance” of its baroclinic component circulation, suggestion that the component circulation precedes the system itself in variation; iii) the reversal happens when it goes from summer to winter, with the SAH displacement under the “dynamic steering” of its barotropic component circulation.     

El Nino演变不同阶段东亚大气环流年际异常型的数值模拟

给定1948～1999年逐月变化的全球观测的海表温度分布，使用全球大气环流模式（CCM3/NCAR）模拟了大气对海表温度变化的响应，利用SVD和合成检验方法，分析了El Nino发展阶段夏季、成熟阶段冬季以及衰亡阶段夏季东亚大气环流的年际异常型.结果表明：El Nino发展阶段夏季，中国东北、朝鲜半岛以及日本海附近为高度负异常中心，西太平洋副高偏弱、偏东，东亚夏季风增强；El Nino成熟阶段冬季，东亚大槽加强，东亚北部冬季风加强；El Nino衰亡阶段夏季，西太平洋副高偏强、偏南、西伸，东亚夏季风减弱；El Nino事件在其衰亡阶段夏季与东亚大气环流异常的关系最紧密，其次是成熟阶段冬季，最后是发展阶段夏季.模拟的El Nino演变不同阶段东亚大气环流年际异常型易于解释以往研究中观测分析揭示的由El Nino造成的我国东部气温和降水异常型.     

东北和华北东部气温异常特征及其成因的初步分析

采用REOF，SVD分析方法，首先指出东北和华北东部气温异常是全国气温异常的第一主分量，进而分析其异常特征及成因。结果表明：全区年、季气温均呈上升趋势，其中冬季增温最大，极端低温较极端高温升高明显。近百年来，全区增温幅度明显高于20世纪全球平均增暖水平。冬季，对流层中、低层上，当纬向西风偏强时，东北和华北东部易高温；而当经向风强盛时，易低温。夏季，气温异常与东北冷涡活动有关；1980年代以来气温显著变暖与对流层中、低层气压场的年代际突变有关。冬夏季气温与东亚冬夏季风、Nino3区海温的关系并不显著，但在1990年代以前，东北夏季低温与El Nino的对应关系较好。     

东准噶尔海相火山岩型小瑞江铜矿地质特征及其找矿方向

在西伯利亚板块库兰卡孜干晚古生代岛弧上，古亚洲洋壳对西伯利亚古陆南缘俯冲一碰撞不同阶段形成了多种类型的金、铜、汞矿床（点），新发现的产在下泥盆统细碧岩中的海相火山岩型小瑞江铜矿，地表铜化矿带具有一定规模，铜矿受一定的层位和岩性控制，其特征与海相火山岩黄铁矿型白银铜矿特征相似，属海底基性火山喷流沉积形成的矿床，有着广阔的找矿前景．     

GCM STUDIES ON ANTHROPOGENIC CLIMATE CHANGE IN CHINA*

Impacts of human activities on climate change as simulated by the general circulation models (GCMs)in China for the recent ten years have been summarized and reviewed in this paper.The researches show that it might be getting warmer over China due to the greenhouse effects.The atmospheric circulation and precipitation also might be changed due to the greenhouse effects.The assessments and evaluations of the models over the globe and China have also been presented in this paper.     

中亚蛇绿岩带研究进展及区域构造连接

中亚地区分布着数十条不同时代和不同性南的蛇绿岩带,这些形成于早古生代或新元古代的蛇绿岩带由于受后期构造变动的强破坏,只在极少数地点保存良好。尽管出露分散,确定其时代和性质有一定困难,但其仍具极其重要的构造单元划分、对比和连接意义。在对比和讨论蛇绿岩带的连接时,应以微体化石给出信息为主,同时参考蛇岩下部组分的同位素年代学数据。讨论了新疆东北部邻区和西部邻区蛇绿岩带的时代和性质,以及这些蛇绿岩带的对此     

LARGEST ALTYN TAGH LITHOSPHERIC SHEAR FAULT IN CENTRAL ASIA

LARGEST ALTYN TAGH LITHOSPHERIC SHEAR FAULT IN CENTRAL ASIA     

Evolution of the Academician Ridge Accommodation Zone in the central part of the Baikal Rift, from high-resolution reflection seismic profiling and geological field investigations

 New high-resolution seismic reflection data from the central part of Lake Baikal provide new insight into the structure and stratigraphy of Academician Ridge, a large intra-rift accommodation zone separating the Central and North Baikal basins. Four seismic packages are distinguished above the basement: a thin top-of-basement unit; seismic-stratigraphic unit X; seismic-stratigraphic unit A; and seismic-stratigraphic unit B. Units A and B were cored on selected key locations. The four packages are correlated with a series of deposits exposed on the nearby western shores: the Ularyar Sequence (Oligocene); the Tagay Sequence (Lower to Middle Miocene); the Sasa Sequence (Upper Miocene to Lower Pliocene); the Kharantsy Sequence (Upper Pliocene); and the Nyurga Sequence (Lower Pleistocene). Based on stratal relationships, sedimentary geometries, distribution patterns and principal morphostructural elements – both onshore and offshore – we propose a new palaeogeographic evolution model for the area. In this model progressive tectonic subsidence of the Baikal basins and successive pulses of uplift of various segments of the rift margins lead to: (a) formation of the ridge as a structural and morphological feature separating the Central and North Baikal basins during the Middle to Late Miocene; (b) gradual flooding of the main parts of the ridge and establishment of a lacustrine connection between the two rift basins during the Late Miocene; and (c) total submergence of the top parts of the crest of the ridge during the latest Pleistocene. This new model helps to better constrain numerous phases in the structural evolution of the Baikal Rift, in which the Academician Ridge as an accommodation zone plays a crucial role. Received: 26 November 1999 / Accepted: 12 March 2000