地震预测试验场的回顾与展望   总被引：2，自引：0，他引：2  

吴忠良  张东宁  张国民 《东北地震研究》2001,17(2):1-7

地震预测试验场针对特定的地震危险区，通过密集的、多学科的强化观测，研究与短临地震预测有关的科学问题，作为一类“大科学”项目，地震预测试验场的经验和教训值得认真总结，本文回顾和评述了地震预测试验场的观测与研究，对地震预测试验场的概念进行了分析和讨论，指出新技术的应用赋予地震预测试验场以新的内涵。并为地震预测研究带来新的发展机遇。  相似文献   

夏季青藏高原与热带西太平洋下垫面热源异常对中国短期气候的影响   总被引：3，自引：1，他引：3  

刘晓东  惠小英  陈葆德 《高原气象》1991,(3)

本文利用一个两层全球大气环流格点模式进行了控制试验、青藏高原地表反照率增加及热带西太平洋海温升高等三个数值试验,以研究夏季这两个地区下垫面热源异常对短期气候变化的影响。结果表明,高原地面热源减弱将造成海平面气压场上亚洲大陆低压减弱;高原及其以西地区500 hPa高度下降,黄河以北地区高度升高;同时高原地区、江淮流域以及黑龙江流域降水减少,但从北疆、内蒙到辽河流域以及我国西南局部和东南沿海地区降水增加。热带西太平洋海温异常带来的变化与此不同.文中还就下垫面热源异常在短期气候预测方面的可能应用等问题进行了讨论。  相似文献   

气候变化对陆地生态系统第一性生产力的影响研究综述   总被引：12，自引：0，他引：12  

彭少麟  侯爱敏  周国逸 《地球科学进展》2000,15(6):717-722

气候变化对陆地生态系统第一性生产力(NPP)的影响是一个倍受关注的问题,目前从观测、实验和模拟等几个方面在不同层次上对这个问题进行了大量的研究。气候变化对生态系统NPP的影响取决于气候各因子及其组合变化的方向、生态系统与当前气候之间的关系,另外还要受养分及其它因子的影响。目前大量存在的NPP模型各有优缺点,模拟结果各异但有会聚的趋势。改进观测方法和理论、建立全球共享NPP数据库、进行大规模生态系统层次的实验研究和发展生态系统动态模型(DGVM)是未来一段时期研究的重点。  相似文献   

Bluetooth tracking of humans in an indoor environment: An application to shopping mall visits     

《Applied geography (Sevenoaks, England)》2017

Intelligence about the spatio-temporal behaviour of individuals is valuable in many settings. Generating tracking data is a necessity for this analysis and requires an appropriate methodology. In this study, the applicability of Bluetooth tracking in an indoor setting is investigated. A wide variety of applications can benefit from indoor Bluetooth tracking. This paper examines the value of the method in a marketing application. A Belgian shopping mall served as a real-life test setting for the methodology. A total of 56 Bluetooth scanners registered 18.943 unique MAC addresses during a 19-day period. The results indicate that Bluetooth tracking is a sound approach for capturing tracking data, which can be used to map and analyse the spatio-temporal behaviour of individuals. The methodology also provides a more efficient and more accurate way of obtaining a variety of relevant metrics in the field of consumer behaviour research. Bluetooth tracking can be implemented as a new and cost effective practice for marketing research, that provides fast and accurate results and insights. We conclude that Bluetooth tracking is a viable approach, but that certain technological and practical aspects need to be considered when applying Bluetooth tracking in new cases.  相似文献   

Characteristics of coastal erosion geometry under regular and irregular waves   总被引：1，自引：0，他引：1  

K Günayd?n  M.S Kabda?l? 《Ocean Engineering》2003,30(13):1579-1593

An experimental investigation of coastal erosion generated by the action of regular and irregular waves was carried out in laboratory channels. Natural beach sand, with medium diameter of 0.35 mm and specific gravity of 2.63, was used in this study. A 1:5 initial beach slope was selected for the model tests. Different wave groups were generated over the initially flat beach, and the characteristics of coastal erosion geometry such as erosion lengths, erosion depths, location of maximum erosion point, and total erosion areas were measured. The most important parameters governing coastal erosion were evaluated by using earlier investigations and experimental results. These parameters were expressed as a dimensionless group by using π theory. The empirical relationships between the geometric characteristics of coastal erosion and the dimensionless group are proposed through regression analysis for pure regular waves, pure irregular waves, and regular-irregular waves. The parameters, which were used to define geometric characteristics of coastal erosion, were evaluated and some ratios of these parameters gave a constant value.  相似文献   

Deformation of monochromatic water wave trains propagating over a submerged obstacle in the presence of uniform currents     

M. Hasanat Zaman  Hiroyoshi Togashi  R. Emile Baddour 《Ocean Engineering》2008,35(8-9):823-833

A nonlinear numerical model based on depth averaged equations and a relevant physical model have been investigated for the deformation of the water wave propagating over a submerged parabolic obstacle in the presence of uniform current. Physical and numerical modeling for wave with both following and opposing currents are done to explore the wave evolutions during passage over the submerged obstacle. A third-order Stokes dispersion relation is utilized in some cases in the computation. Separated flow zone is taken into consideration by two empirical equations obtained from the physical model testing done by the authors. Verification and validation of the numerical model by other published theoretical and experimental data are presented.  相似文献   

Effects of topography on lofting gravity flows: Implications for the deposition of deep-water massive sands     

Christopher J. Stevenson  Jeff Peakall 《Marine and Petroleum Geology》2010

Hyperpycnal flows are generated in the marine environment by sediment-laden fresh water discharge into the ocean. They frequently form at river mouths and are also generated in proximal ice-melting settings and are thought to be responsible for transporting a large proportion of suspended river sediment onto and off the continental shelf. Hyperpycnal flows are an example of gravity currents that display reversing buoyancy. This phenomenon is generated by the fresh water interstitial fluid being less dense than that of the ambient seawater. Thus after sufficient particles are sedimented the flow can become positively buoyant and loft, forming a rising plume. Here we present results from physical scale-modelling experiments of lofting gravity currents upon interaction with topography. Topography, in the form of a vertical obstacle, triggered a localised lofting zone on its upstream side. This lofting zone was maintained in a fixed position until the bulk density of the flow had reduced enough to allow lofting along its entire length. The obstructed lofting zone is associated with a sharp increase in deposit thickness. By inference these experimentally established lofting dynamics are applied to improve understanding of the potential for hyperpycnal flows to deposit deep-water massive sands. This study provides a depositional mechanism by which large volumes of sand can be deposited in the absence of traction and the fines removed, leaving thick deposits of structureless sand with a low percentage of mud. This conceptual model for the first time provides a framework by which the geometries of certain deep-water massive sands may be predicted within specific depositional and basinal settings. This is crucial to our understanding of massive sand deposits in modern and ancient turbiditic systems and in the commercial evaluation of hydrocarbon potential of such sedimentary successions.  相似文献   

北京地区暴雨个例的观测敏感区研究   总被引：1，自引：1，他引：0  

李玉焕  张朝林  仲跻芹  孟智勇 《气候与环境研究》2013,18(5):651-661

利用基于集合预报的相关方法对2009年7月23日发生在北京及周边地区的暴雨过程的观测敏感区进行了分析。通过WRF(Weather Research Forecast)三维变分方法对初始场进行随机扰动,形成30个初始集合样本,做了预报时效为12 h的集合预报。利用该方法分析检验区(北京及周边地区)累积降水[14:00(北京时间,下同)至20:00]相对于初始时刻(08:00)各基本要素的敏感性,确定感性要素及其对应的区域。研究发现初步确定的敏感性要素为水汽和温度,对应的敏感区分别位于北京的西南侧和北京的东北侧,且通过实况分析可知初步确定的敏感性要素和对应的敏感区具有明确的物理意义。还进一步通过观测系统模拟试验(OSSE)的资料同化验证所确定的敏感区,结果表明在水汽对应的敏感区内同化水汽对降水的预报结果有明显的改进;在温度对应的敏感区内同化温度,降水的预报准确率有了明显的提高,说明了初步确定的敏感性要素和敏感区的正确性。在水汽对应的敏感区内同化水汽的同时在温度对应的敏感区内同化温度,使降水预报的技巧有大幅度的提高,说明了温度和水汽的共同作用对提高降水预报准确率贡献最大。因此,通过基于集合预报的相关方法能够快速的确定敏感区。研究结果将为确定北京暴雨的观测敏感区提供参考。  相似文献   

海峡两岸及邻近地区暴雨试验研究的进展     

徐宝祥  周秀骥 《高原气象》1999,18(3):436-440

“海峡两岸及邻近地区暴雨试验研究”项目经数载酝酿,筹划,在各界气象同行和有关人干的积极推动和部门的大力支持下,最后获批准并列为国家“九．五”攀登计划志项,并在１９９８年取得了重要进展。本文概要介绍这一项目的科学目标,研究 近期研究的进展。  相似文献   

台风路径实时数值预报的初步试验   总被引：5，自引：1，他引：5       下载免费PDF全文

王诗文  李健军 《应用气象学报》1994,5(4):462-469

根据国家气象中心建立的台风路径数值预报试验系统，引入了模型台风。模型台风是利用获得的场面参数构成的，然后再叠加到客观分析场上作为台风路径预报的初始场。引入模型台风后，无论是台风中心位置还是其流场、质量场与实际观测比较接近，且预报效果有一定提高。利用模型台风对1992年Eli（9205号）和Janis（9210号）台风进行了实时的预报试验。结果表明对这二个台风的移动趋势基本上能预报出来，预报的台风路径与实况进行了对比，并与气候持续预报作了比较，效果较好。  相似文献