Recent Progress in the Impact of the Tibetan Plateau on Climate in China   总被引：14，自引：0，他引：14  

刘屹岷  包庆  段安民  钱正安  吴国雄 《大气科学进展》2007,24(6):1060-1076

Studies of the impacts of the Tibetan Plateau （TP） on climate in China in the last four years are reviewed. It is reported that temperature and precipitation over the TP have increased during recent decades. From satellite data analysis, it is demonstrated that most of the precipitation over the TP is from deep convection clouds. Moreover, the huge TP mechanical forcing and extraordinary elevated thermal forcing impose remarkable impacts upon local circulation and global climate. In winter and spring, stream flow is deflected by a large obstacle and appears as an asymmetric dipole, making East Asia much colder than mid Asia in winter and forming persistent rainfall in late winter and early spring over South China. In late spring, TP heating contributes to the establishment and intensification of the South Asian high and the abrupt seasonal transition of the surrounding circulations. In summer, TP heating in conjunction with the TP air pump cause the deviating stream field to resemble a cyclonic spiral, converging towards and rising over the TP. Therefore, the prominent Asian monsoon climate over East Asia and the dry climate over mid Asia in summer are forced by both TP local forcing and Eurasian continental forcing.
Due to the longer memory of snow and soil moisture, the TP thermal status both in summer and in late winter and spring can influence the variation of Eastern Asian summer rainfall. A combined index using both snow cover over the TP and the ENSO index in winter shows a better seasonal forecast.
On the other hand, strong sensible heating over the Tibetan Plateau in spring contributes significantly to anchor the earliest Asian monsoon being over the eastern Bay of Bengal （BOB） and the western Indochina peninsula. Qualitative prediction of the BOB monsoon onset was attempted by using the sign of meridional temperature gradient in March in the upper troposphere, or at 400 hPa over the TP. It is also demonstrated by a numerical experiment and theoretical study that the heating over the TP lea  相似文献   

Progress in Predictability Studies in China （2003-2006）     

段晚锁  姜智娜  徐辉 《大气科学进展》2007,24(6):1086-1098

Since the last International Union of Geodesy and Geophysics General Assembly(2003),predictability studies in China have made significant progress.For dynamic forecasts,two novel approaches of conditional nonlinear optimal perturbation and nonlinear local Lyapunov exponents were proposed to cope with the predictability problems of weather and climate,which are superior to the corresponding linear theory.A possible mechanism for the"spring predictability barrier"phenomenon for the El Ni(?)o-Southern Oscillation (ENSO)was provided based on a theoretical model.To improve the forecast skill of an intermediate coupled ENSO model,a new initialization scheme was developed,and its applicability was illustrated by hindcast experiments.Using the reconstruction phase space theory and the spatio-temporal series predictive method, Chinese scientists also proposed a new approach to improve dynamical extended range(monthly)prediction and successfully applied it to the monthly-scale predictability of short-term climate variations.In statistical forecasts,it was found that the effects of sea surface temperature on precipitation in China have obvious spatial and temporal distribution features,and that summer precipitation patterns over east China are closely related to the northern atmospheric circulation.For ensemble forecasts,a new initial perturbation method was used to forecast heavy rain in Guangdong and Fujian Provinces on 8 June 1998.Additionally, the ensemble forecast approach was also used for the prediction of a tropical typhoons.A new downscaling model consisting of dynamical and statistical methods was provided to improve the prediction of the monthly mean precipitation.This new downsealing model showed a relatively higher score than the issued operational forecast.  相似文献   

武汉市汤逊湖沉积物重金属垂向变化的磁响应特征及环境意义   总被引：3，自引：1，他引：3       下载免费PDF全文

段雪梅  胡守云  杨涛 《第四纪研究》2007,27(6):1105-1112

对武汉汤逊湖湖泊沉积物T06-1样芯进行了磁性测量、重金属分析和粒度分析,探讨了利用磁参数追踪、指示城市湖泊重金属污染的可行性.结果表明,低矫顽力的亚铁磁矿物主导了沉积物的磁性特征.磁参数χ,SIRM和ARM与重金属Cr,Zn,Cu和Pb呈现较为一致的垂向变化特征:55cm之下,磁参数值和重金属的含量均较低且稳定;在50～10 cm之间,两者基本呈现随深度的减小而增加的趋势,其中在20～10 cm区间,出现小范围内波动;而10cm至表层,元素含量和磁参数值随深度减小而急剧增加.选取粘土(＜4μm)对沉积物中Cr,Zn,Cu和Pb进行粒度校正的结果显示:校正后元素的变化趋向于平稳,但在表层的10cm处Cr,Pb,Zn和Cu的含量仍然较高,表明了表层沉积物中金属元素的含量主要受人类活动的影响.相关分析也表明了磁参数χ,SIRM和ARM与重金属Cr,Pb,Zn和Cu之间均呈显著相关关系(0.62≤R≤0.86),表明磁参数可以用于追踪和指示汤逊湖湖泊沉积物重金属污染.  相似文献   

新疆伽师强震群区基底界面结构特征   总被引：3，自引：0，他引：3       下载免费PDF全文

徐朝繁  段永红  田晓峰  潘纪顺  张建狮  胡修奇 《地震学报》2007,29(5):477-482

用射线分布分析法对伽师强震群区的高分辨折射地震剖面资料进行了更进一步的分析处理， 得到了伽师强震群区更完整的基底界面结构特征. 结果表明，在伽师强震群区地壳上部存在两个明显的结构界面:第一个界面的结构连续、完整，其埋深变化不大， 在2.6～3.3 km之间，为一向天山方向逐渐抬升、 近平直的倾斜界面；第二个界面的埋深变化较大， 在8.5～11.8 km之间，为古老的塔里木盆地结晶基底. 在约37 km桩号附近结晶基底有近2.5 km的深度突变， 推断可能是伽师强震群区超基底断裂所致. 以该断裂为界，结晶基底分为西南、东北两段. 每段内界面的埋深变化不大， 西南段的埋深约11.5 km， 东北段的埋深约为8.5～9.0 km，该段在从西南向东北整体抬升的背景上略有上隆，反映出在塔里木地块西北缘特殊的构造环境下上部地壳的变形特征.   相似文献   

Dynamical effects of environmental vertical wind shear on tropical cyclone motion, structure, and intensity     

X. Zheng  Y. H. Duan  H. Yu 《Meteorology and Atmospheric Physics》2007,97(1-4):207-220

Summary A series of numerical experiments on an f plane are conducted using the fifth-generation Pennsylvania State University-National Center for Atmospheric Research Mesoscale Model, version 3 (MM5) to investigate how environmental vertical wind shear affects the motion, structure, and intensity of a tropical cyclone. The results show that a tropical cyclone has a motion component perpendicular to the vertical shear vector, first to the right of the shear and then to the left. An initially axisymmetric, upright tropical cyclone vortex develops a downshear tilt and wavenumber-one asymmetry when embedded in environmental vertical wind shear. In both small-moderate shears, a storm weakens slightly compared to that in a quiescent environment. The circulation centers between 300 hPa and the surface varies from 20 km to over 80 km. The secondary circulation becomes quite asymmetric about the surface cyclone center. As a result, convection on the upshear-right quadrant diminishes, limiting the upward heat transport in the eyewall and thus lowering the warm core and leading to a weakening of the storm. In strong vertical shear (above 12 m s⁻¹), the vertical tilt exceeds 160 km in 48 h of simulation and the secondary circulation on the upshear side is completely destroyed with low-level outflow. The axisymmetric component of eyewall convection weakens remarkably and becomes much less penetrative. As a result, the warm core becomes weak and appears at lower levels and the storm weakens rapidly accordingly. This up-down weakening mechanism discussed in this study is different from those previously discussed. It emphasizes the penetrative role of eyewall convection in transporting heat from the ocean to the mid-upper troposphere, maintaining the warm core structure of the tropical cyclone. The vertical shear is found negative to eyewall penetrative convection.  相似文献   

基于GIS城市给排水管网信息系统数据结构的研究与实现     

武文波  段权  刘金生 《测绘与空间地理信息》1998,(2)

本文研究了城市给排水管网信息系统的数据结构及其建立方法,以及在微机上利用C语言进行城市给排水信息系统的设计,实现了部分空间分析功能。  相似文献   

洪湖日本沼虾的种群繁殖生物学   总被引：6，自引：0，他引：6  

孙建贻  张道源  段中华  谭德清 《湖泊科学》1998,(2)

1994年5月至1995年6月对洪湖日本沼虾的种群繁殖生物学进行了研究．洪湖日本沼虾的繁殖期为4月中旬至10月上旬,5月中旬至8月中旬为日本沼虾的繁殖高峰期,其中6月、8月雌虾抱卵率均在70％以上;日本沼虾群体中雄性总是少于雌性,月性比（♀／♂）变化于1．104－5．780之间,3—6月性比逐渐增高,7─10月性比则逐渐降低;在整个繁殖期．4─7月的抱卵虾均为前一年出生的大、中规格的个体,之后当年出生的个体在繁殖群体中逐渐占据优势;春季抱卵虾的绝对繁殖力和相对繁殖力都大于秋季抱卵虾,分别计算了绝对繁殖力、相对繁殖力与体长、体重的函数关系．本文还对日本沼虾群体性比的周年变化及其产卵次数进行了讨论．  相似文献   

Three dimensional large scale earthquake simulator with six degrees of freedom     

Jun-Wei Han  Yu-Ting Li  Bao-Sheng Hu 《地震学报(英文版)》1998,11(3):387-390

Conclusions When the aseismic test of large scale structure is performed, it is a major performance that the actual response waveform is identical to the input signal waveform under the condition of analog control, especially when the damping of the structure tested is small. The rotational motions of the simulator are induced due to the structure inertia, so that it is a key technique for the simulator design that realizes independent control of the simulator with six degrees of freedom and suppresses the rotational motions. In the design, the modern control techniques are applied and a high performance of the three dimensional earthquake simulator is developed successfully. The simulator can simulate actual earthquake load and it is an important test device for aseismic research. This paper is a main project of the Eighth Five Plan, State Seismological Bureau.  相似文献   

论德尔尼黄铁矿型铜钴矿床的地质特征及其与塞浦路斯铜矿的区别   总被引：2，自引：0，他引：2  

段国莲 《化工矿产地质》1998,(4)

通过对德尔尼铜钴矿床与塞浦路斯铜矿的对比,进一步明确了德尔尼铜钴矿床为与印支期黑云花岗岩有成因联系的岩浆热液矿床。矿区的超基性岩或超基性火山角砾岩都是不含矿的,与矿床无成因联系;底辟上升侵位也不存在。将德尔尼铜钴矿床作为火山岩块状硫化物矿床系列中的最基性端员缺乏依据。  相似文献   

《县市级变更调查软件》在国土部门应用解析     

段兰香 《内蒙古地质》1998,(4)

本软件是在菜单环境下工作,包括如下几大功能：１．系统维护２．建立电子台帐３．变更调查记录表４．变更后台帐５．打印输出６．台帐结转为用户设计了满意舒适的工作环境,对于一位不懂计算机的工作人员来讲,只用很短的时间,就可掌握软件使用的全过程。以一种十分便捷和廉价的方法,为国土工作者提供了一秒钟量算一个复杂图斑面积的强大能力。电子台帐的建立可进行查询、整理、归集和打印,并且很方便地进行当年变更调查内业工作,形成变更后台帐,并轻而易举地结转为下一年度的变更前台帐库,以满足国家局变更调查工作的全部要求。  相似文献