虚假回波在强对流天气探测中的应用   总被引：1，自引：0，他引：1  

谢向阳赵学军  李建刚孔团结 王梅英 《沙漠与绿洲气象(新疆气象)》2005,28(2):26-27

根据2003年几次强对流天气的观测资料，对其中三体散射长钉、二次回波旁瓣回波等虚假回波进行了分析。初步得出了上述虚假回波在新一代C波段天气雷达图像上的特征，为强对流天气的雷达探测和识别提供一些依据。  相似文献   

一次“高影响天气”的弱降雪过程的数值研究   总被引：11，自引：2，他引：11       下载免费PDF全文

蒋建莹史历  倪允琪 《应用气象学报》2005,16(2):231-237

该文对2001年12月7日下午北京的一次弱降雪天气过程进行了诊断分析和数值模拟研究。诊断结果表明:北京地区由于受500 hPa小槽东移及850 hPa东移小高压后部带来的来自东海和南海的偏南暖湿气流共同影响，造成降雪。数值模拟结果显示:MM5模式对这次降雪过程具有较好的模拟能力，不仅模拟出了北京地区的降雪量，而且对这次过程大尺度背景场的演变、触发机制和水汽源有很好的表述。利用诊断分析和数值模拟结果，对这次弱降雪过程引起交通大阻塞的可能因素进行了探讨，说明建立城市预警系统的迫切性。  相似文献   

梅雨锋云系的结构特征及其成因分析   总被引：7，自引：9，他引：7  

姚秀萍  于玉斌  赵兵科 《高原气象》2005,24(6):1002-1011

利用逐时卫星遥感观测资料和地面测站的降水资料，分析了江淮流域2003年6月22～26日暴雨过程中梅雨锋云系的演变、结构特征和形成原因。结果表明，梅雨锋云系为一条TBB的低值带，稳定少动，其上分布着中尺度对流系统（MCS），而中尺度对流系统是由不同尺度、不同强度．的对流单体（包括中β和中γ尺度对流单体）组成的，从而使得梅雨锋云系产生不均匀的降水分布（包括时间上和空间上）。在该暴雨过程中，梅雨锋云系充分体现了中尺度对流系统中所包括的3类组织结构形式。梅雨锋云系与中高纬度云系或热带辐合带云系之间的相互作用与暴雨过程关系密切，梅雨锋云系的维持和发展与强大的黄淮气旋云系直接相关，它是江淮流域上空冷暖气流交汇的结果。  相似文献   

Effects of detailed soil spatial information on watershed modeling across different model scales     

Trevor Quinn  A.-Xing Zhu  James E. Burt   《International Journal of Applied Earth Observation and Geoinformation》2005,7(4):324-338

Hydro-ecological modelers often use spatial variation of soil information derived from conventional soil surveys in simulation of hydro-ecological processes over watersheds at mesoscale (10–100 km²). Conventional soil surveys are not designed to provide the same level of spatial detail as terrain and vegetation inputs derived from digital terrain analysis and remote sensing techniques. Soil property layers derived from conventional soil surveys are often incompatible with detailed terrain and remotely sensed data due to their difference in scales. The objective of this research is to examine the effect of scale incompatibility between soil information and the detailed digital terrain data and remotely sensed information by comparing simulations of watershed processes based on the conventional soil map and those simulations based on detailed soil information across different simulation scales. The detailed soil spatial information was derived using a GIS (geographical information system), expert knowledge, and fuzzy logic based predictive mapping approach (Soil Land Inference Model, SoLIM). The Regional Hydro-Ecological Simulation System (RHESSys) is used to simulate two watershed processes: net photosynthesis and stream flow. The difference between simulation based on the conventional soil map and that based on the detailed predictive soil map at a given simulation scale is perceived to be the effect of scale incompatibility between conventional soil data and the rest of the (more detailed) data layers at that scale. Two modeling approaches were taken in this study: the lumped parameter approach and the distributed parameter approach. The results over two small watersheds indicate that the effect does not necessarily always increase or decrease as the simulation scale becomes finer or coarser. For a given watershed there seems to be a fixed scale at which the effect is consistently low for the simulated processes with both the lumped parameter approach and the distributed parameter approach.  相似文献   

笛卡儿坐标系的双多普勒天气雷达三维风场反演技术   总被引：27，自引：9，他引：27  

周海光  张沛源 《气象学报》2002,60(5):585-593

文中研究了笛卡尔坐标系下双多普勒天气雷达三维风场反演技术 ,提出了包括雷达原始资料的预处理 ,空间插值以及可靠性检验的新方法 ,提高了反演结果的可信度和精确度。使用模拟的双多普勒雷达体扫资料进行了反演试验 ,结果表明 :本文的方法能够比较真实地反映风场的三维结构 ,可以用于真实风场的反演。  相似文献   

新疆雷暴天气过程分型   总被引：5，自引：0，他引：5  

王旭  马德荣 《沙漠与绿洲气象(新疆气象)》2002,25(1):8-9

对新疆39a雷暴天气资料的普查，得到367次雷暴天气过程，归结出4种天气形势，雷暴天气由冷锋和中尺度高压造成。  相似文献   

一类广义Hamilton系统的辛格式     

Zhao Ying  Wang Bin  Ji Zhongzhen 《大气科学进展》2002,19(4):719-726

通过引人泊松括号，分析了无限维Hamilton的性质，并将其推广到广义Hamilton系统，且从理论和实用角度讨论了这类广义Hamilton系统的辛格式构造问题，从而为辛几何算法在一般的时间发展方程的数值求解提供新的具体途径。  相似文献   

Seismic response of self‐centring hysteretic SDOF systems     

Constantin Christopoulos  Andr Filiatrault  Bryan Folz 《地震工程与结构动力学》2002,31(5):1131-1150

The seismic response of single‐degree‐of‐freedom (SDOF) systems incorporating flag‐shaped hysteretic structural behaviour, with self‐centring capability, is investigated numerically. For a SDOF system with a given initial period and strength level, the flag‐shaped hysteretic behaviour is fully defined by a post‐yielding stiffness parameter and an energy‐dissipation parameter. A comprehensive parametric study was conducted to determine the influence of these parameters on SDOF structural response, in terms of displacement ductility, absolute acceleration and absorbed energy. This parametric study was conducted using an ensemble of 20 historical earthquake records corresponding to ordinary ground motions having a probability of exceedence of 10% in 50 years, in California. The responses of the flag‐shaped hysteretic SDOF systems are compared against the responses of similar bilinear elasto‐plastic hysteretic SDOF systems. In this study the elasto‐plastic hysteretic SDOF systems are assigned parameters representative of steel moment resisting frames (MRFs) with post‐Northridge welded beam‐to‐column connections. In turn, the flag‐shaped hysteretic SDOF systems are representative of steel MRFs with newly proposed post‐tensioned energy‐dissipating connections. Building structures with initial periods ranging from 0.1 to 2.0s and having various strength levels are considered. It is shown that a flag‐shaped hysteretic SDOF system of equal or lesser strength can always be found to match or better the response of an elasto‐plastic hysteretic SDOF system in terms of displacement ductility and without incurring any residual drift from the seismic event. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

A recursive decomposition algorithm for network seismic reliability evaluation     

Jie Li  Jun He 《地震工程与结构动力学》2002,31(8):1525-1539

A new probabilistic analytical approach to evaluate seismic system reliability of large lifeline systems is presented in this paper. The algorithm takes the shortest path from the source to the terminal of a node weight or edge weight network as decomposition policy, using the Boolean laws of set operation and probabilistic operation principal, a recursive decomposition process then could be constructed. For a general weight network, the modified Torrieri method (NTR/T method) is introduced to combine with the suggested algorithm. Therefore, the recursive decomposition algorithm may be applied to evaluate the seismic reliability of general lifeline systems. A series of case studies, including a practical district electric power network system and a large urban water supply system, show that the suggested algorithm supplies a useful probabilistic analysis means for the seismic reliability evaluation of large lifeline systems. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

A response‐based decoupling criterion for multiply‐supported secondary systems     

Samit Ray Chaudhuri  Vinay K. Gupta 《地震工程与结构动力学》2002,31(8):1541-1562

It is often infeasible to carry out coupled analyses of multiply‐supported secondary systems for earthquake excitations. ‘Approximate’ decoupled analyses are then resorted to, unless the response errors due to those are significantly high. This study proposes a decoupling criterion to identify such cases where these errors are likely to be larger than an acceptable level. The proposed criterion is based on the errors in the primary system response due to decoupling and has been obtained by assuming (i) the input excitation to be an ideal white noise process, (ii) cross‐modal correlation to be negligible, and (iii) the combined system to be classically damped. It uses the modal properties of the undamped combined system, and therefore, a perturbation approach has been formulated to determine the combined system properties in case of light to moderately heavy secondary systems. A numerical study has been carried out to illustrate the accuracy achieved with the proposed perturbation formulation. The proposed decoupling criterion has been validated with the help of two example primary‐secondary systems and four example excitation processes. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献