Late Tremadoc and Early Floian Graptolites from Central Hunan, China     

LI Ming  FENG Hongzhen  JI Xinxin  LI Lixia 《《地质学报》英文版》2010,84(6):1343-1364

<正>Fourteen graptolite species of the Late Tremadoc and Early Floian are described from the Nanba section in the Yiyang area,Hunan Province.Among them,Paradelograptus onubensis, Kiaerograptus bulmani,K.kutchini and Paratemnograptus isolatus of the Late Tremadoc are first found in China.Based on the current graptolite materials,the correspondingly complete graptolite zones of Upper Tremadocian in China are recognized as follows(in ascending order):the Adelograptus tenellus Zone,the Aorograptus victoriae Zone,the Araneograptus murrayi Zone and the Hunnegraptus copiosus Zone.In the Nanba section,the Hunnegraptus copiosus Zone is overlain directly by the Tetragraptus approximatus Zone,there is no hiatus below the base of Floian.  相似文献   

Systematic errors in the medium range prediction of the Asian summer monsoon circulation     

U. C. Mohanty  K. J. Ramesh 《Journal of Earth System Science》1995,104(1):49-77

The present study describes an analysis of Asian summer monsoon forecasts with an operational general circulation model (GCM) of the European Centre for Medium Range Weather Forecasts (ECMWF), U.K. An attempt is made to examine the influence of improved treatment of physical processes on the reduction of systematic errors. As some of the major changes in the parameterization of physical processes, such as modification to the infrared radiation scheme, deep cumulus convection scheme, introduction of the shallow convection scheme etc., were introduced during 1985–88, a thorough systematic error analysis of the ECMWF monsoon forecasts is carried out for a period prior to the incorporation of such changes i.e. summer monsoon season (June–August) of 1984, and for the corresponding period after relevant changes were implemented (summer monsoon season of 1988). Monsoon forecasts of the ECMWF demonstrate an increasing trend of forecast skill after the implementation of the major changes in parameterizations of radiation, convection and land-surface processes. Further, the upper level flow is found to be more predictable than that of the lower level and wind forecasts display a better skill than temperature. Apart from this, a notable increase in the magnitudes of persistence error statistics indicates that the monsoon circulation in the analysed fields became more intense with the introduction of changes in the operational forecasting system. Although, considerable reduction in systematic errors of the Asian summer monsoon forecasts is observed (up to day-5) with the introduction of major changes in the treatment of physical processes, the nature of errors remain unchanged (by day-10). The forecast errors of temperature and moisture in the middle troposphere are also reduced due to the changes in treatment of longwave radiation. Moreover, the introduction of shallow convection helped it further by enhancing the vertical transports of heat and moisture from the lower troposphere. Though, the hydrological cycle in the operational forecasts appears to have enhanced with the major modifications and improvements to the physical parameterization schemes, certain regional peculiarities have developed in the simulated rainfall distribution over the monsoon region. Hence, this study suggests further attempts to improve the formulations of physical processes for further reduction of systematic forecast errors.  相似文献   

Anomalously deep earthquakes in northwestern Italy     

Marco Cattaneo  Paolo Augliera  Stefano Parolai  Daniele Spallarossa 《Journal of Seismology》1999,3(4):421-435

It is usually assumed that earthquakes in intraplate regions occur in the upper crust, and northwestern Italy is generally assigned to this kind of normal seismicity. In this work, the depth distribution of the events localized in this area by the Istituto Geofisico Geodetico (IGG) seismic network in the period 1991–1997 is analyzed in detail. In particular, the location capability of the network is discussed, adopting as reference quarry blasts (for the epicentral position) and the locations obtained from a dense temporary network (for the depth estimate). Within the so-obtained error limits, the depth distribution of events show a characteristic pattern: while for most of the area covered by the network the well-located seismicity lies within the first 20 km of depth, in a band following the inner arc of the Western Alps, numerous events have anomalously large focal depths, reaching a maximum of 114 km. These depth determinations cannot be attributed to instabilities of the location procedure: different choices of the propagation models used for the hypocentral determination led to very similar depth values, always significantly larger than the standard values for the surrounding areas. A strong correlation has been found between the 3-dimensional distribution of these foci and the P-wave propagation anomalies obtained from tomographic studies, suggesting a direct link between elastic and rheological properties of lower crust and upper mantle in this area.  相似文献   

卡尔曼滤波模型误差的识别   总被引：3，自引：1，他引：2  

陶本藻 《大地测量与地球动力学》1999,19(4):15-20

本文在简述卡尔曼滤波模型基础上讨论了模型误差的检验和估计问题,提出了检验卡尔曼滤波模型误差显著性的几种统计假设检验方法,探讨并给出了估计模型误差的方法和公式。  相似文献   

基于集合预报的台风“利奇马”登陆后远距离暴雨预报的敏感性分析     

王毅  张晓美  陶亦为  刘爽  邓国 《气象科学》2020,40(1):22-29

2019年第9号台风“利奇马”在8月10日登陆后引发了远距离大范围的暴雨,本文利用ECMWF(EC)和GRAPES全球集合预报模式等资料对暴雨短期预报的误差及原因进行了分析。此次台风远距离暴雨主要集中在8月10日夜间的山东中部地区,EC集合预报对该区域的降水量预报效果总体优于GRAPES集合预报。集合敏感性分析可以识别出和预报变量高相关(敏感)的天气系统,结果表明山东区域平均降水量对同期500 hPa副高、台风西北侧海平面气压和山东北部低层温度较为敏感,而对流层高层的高度及经向风存在更大范围的敏感区。根据暴雨预报TS评分选取EC集合预报成员作为优势组和劣势组,结果表明优势组预报成员表现为山东上空300 hPa低槽前倾,北侧高空偏南急流更强,同时配合低层台风外围偏东风急流,形成高层辐散、低层辐合的有利条件。另外,优势组预报的中纬度低层冷空气和斜压锋区更强,导致优势组在山东中部预报出暴雨,更加接近于实况。  相似文献   

地震前兆信息系统的信息分解与浓缩     

刘文义 《地震》1993,(5):18-23

本文运用数值分类学中的因子分析方法,试图从多种前兆观测时序集中浓缩与分解出与地震孕育发生有关的成因信息。并用诸如“地震过程”这样一些概念来代表和归纳一组互相紧密相关的前兆现象和特征。这是与孕震系统在统一区域应力场作用下的整体性行为及子系统之间的协同关联运动的事实在思路上是相一致的。若干震例的研究结果表明,数值分类学是我们实现多台站、多手段,时、空动态综合预报思路的一种较好的方法。  相似文献   

复杂地形条件下嵌套细网格模式35例数值预报的总结     

钱正安  陈玉春 《高原气象》1994,13(2):144-152

本文利用一适合复杂地形区的有限区域预报模式系统，分别采用欧洲中期天气预报中心的格点资料和我国国家气象中心的ＤＣＤ电码资料，对１９８１年７月１－３０日和１９８８年８月１０－１４日两时段共３５天作了４８小时预报。形势场和降水预报的主客观评分表明，该模型系统已具备了在业务环境下作预报的可能，该模型预报性能良好，具有较好的强降水预报的能力。  相似文献   

A new Mississippian dasyclad alga (Chlorophyta) from SW Spain: Implications for the reproductive evolution of the dasyclads during the Late Palaeozoic     

Pedro Cózar  Daniel Vachard 《Eclogae Geologicae Helvetiae》2004,97(2):175-181

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轨道误差对近实时GPS遥感水汽的影响研究   总被引：5，自引：3，他引：5  

曹云昌  方宗义夏青 《气象科技》2004,32(4):229-232

利用GPS技术近实时探测水汽对于气象预报、气候研究具有重要的应用价值，而近实时探测需要使用GPS卫星的预报星历，预报星历的误差会直接影响到实时水汽探测的精度。利用从IGS资料处理中心下载的精密预报星历和最终星历，对2000年北京GPS水汽试验中的资料进行了解算，并结合探空资料计算的水汽进行了分析。结果表明：以探空为标准，使用精密预报星历计算的水汽总量均方根误差为0．31cm，最终星历为0．30cm，二者差别不大，为0．01cm，证明使用精密预报星历可以满足近实时探测水汽的要求。  相似文献   

Material referred to Megalosaurus (Dinosauria: Theropoda) from the Middle Jurassic of Stonesfield, Oxfordshire, England: one taxon or two?     

Julia J. Day 《Proceedings of the Geologists' Association. Geologists' Association》2004,115(4):359-366

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