On the stability of a coupled ocean atmosphere system in the presence of wave-CISK     

Sudha Selvarajan  B. N. Goswami 《Journal of Earth System Science》1992,101(2):153-176

The stability of a simple coupled ocean-atmosphere system similar to the one studied by Hirst with general ocean thermodynamics is investigated in which the atmospheric heating is determined by sea surface temperature anomalies as well as the convergence feedback (low level moisture convergence by the waves themselves). It is shown that the unstable coupled mode found by Hirst (UH mode) is profoundly modified by the convergence feedback. The feedback increases the unstable range of the UH mode and can increase its growth rate several folds. The maximally growing UH mode can become westward propagating for certain strength of convergence feedback. If the convergence feedback strength exceeds a critical value, several new unstable intraseasonal modes are also introduced. These modes are basically ‘advective’ modes. For relatively weak strengths of the convergence feedback the growth rates of these modes are smaller than that of the UH mode. As the atmosphere approaches ‘moist neutral’ state, the growth rates of these modes could become comparable or even larger than that of the UH mode. It is argued that these results explain why the El Nino and Southern Oscillation (ENSO) signal is clear in the eastern Pacific but not so in the western Pacific and they may also explain some of the differences between individual ENSO events. Our results also explain the aperiodic behaviour of some coupled numerical models. Importance of this process in explaining the observed aperiodicity of the ENSO phenomenon is indicated.  相似文献   

适用于遥感领域的交互式图像处理系统     

余旭初 《测绘学院学报》1995,(2)

数字图像处理技术的广泛应用使很多与图像相关的领域产生了根本性的变革。反过来，这些变革也对数字图像处理提出更高的要求，而计算机和人工智能技术的迅速发展为建立新的、面向具体应用的图像处理系统提供了现实的可能性。本文展示了一个基于Ｕｎｉｘ工作站的、适用于遥感领域的交互式图像系统的设计框架和主要功能。  相似文献   

论海洋界面测量学的建立     

刘雁春  梁开龙 《地球科学进展》1995,10(6):542-545

论述了建立海洋界面测量学这一新学科支的背景，对海洋界面测量学的定义及其研究内容进行了探讨，同时论述了它与相关学科的联系，并由此对海洋测量学乃至整个测量学做了进一步思考，提出了一些新的看法。  相似文献   

速度光滑对反射地震信号的影响分析          下载免费PDF全文

魏脯力  孙建国  孟祥羽  徐杨杨  刘明忱  商耀达 《地球物理学报》1954,63(10):3849-3856

光滑处理使得单界面成为非均匀薄层,界面反射转变为层反射.为了探讨光滑处理的影响,以平面波作为入射波场,首先利用过渡层反射系数推导了反射信号的理论公式,然后就非均匀薄层下反射系数的计算问题,给出了具体的实现算法,并通过与经典Epstein过渡层反射系数解析结果的对比说明了算法的精度.最后在单界面及其被光滑后界面的对比分析中,得出了几点重要结论：随着光滑次数的增加,反射信号的到时基本保持不变,而反射信号的主频与能量呈减少趋势,其中信号能量在低光滑次数的衰减速率明显大于高光滑次数.  相似文献   

Dynamic stress concentration and scattering of SH-wave by interface elliptic cylindrical cavity     

陈志刚  刘殿魁  杨在林 《地震工程与工程振动(英文版)》2003,2(2):299-306

In this paper, the dynamic stress concentration and scattering of SH-waves by bi-naterial structures that possess an interface elliptic cavity are investigated. First, by using the complex function method, the Green‘s function is constructed. This yields the solution of the displacement field for an elastic half space with a semi-elliptic canyon impacted by an anti-plane harmonic line source loading on the horizontal surface. Then, the problem is divided into an upper and lower half space along the horizontal interface, regarded as a harmony model. In order to satisfythe integral continuity condition,the unknown anti-plane forces are applied to the interface. The integral equations with unknown forces can be established through the continuity condition, and after transformation, the algebraic equations are solved numerically. Finally, the distribution of the dynamic stress concentration factor (DSCF) around the elliptic cavity is given and the effect of different parameters on DSCF is discussed.  相似文献   

Moving boundaries in transboundary air pollution co-production of science and policy under the convention on long range transboundary air pollution     

Willemijn Tuinstra  Leen Hordijk  Carolien Kroeze 《Global Environmental Change》2006,16(4):349-363

This article focuses on the science–policy interaction in international negotiations in the context of the United Nations Economic Commission for Europe's Convention for Long Range Transboundary Air Pollution (CLRTAP). It addresses the question how participants in the assessment process divide and co-ordinate work between science and policy and how this enhances credibility, legitimacy and relevance with multiple audiences. For this purpose the article combines an analytical framework to approach effectiveness of scientific assessment in policy making, with the notion of boundary work and co-production of science and policy. The article argues that knowledge produced within the CLRTAP process and the institutional setting in which this knowledge production takes place cannot be separated from each other. Furthermore credibility, legitimacy and relevance are to a large extent determined by boundary work in an early stage of the process. At the same time boundary work has to take place continuously in order keep the assessment process credible, legitimate and relevant for new audiences. The application of a combined framework for analysing credibility, legitimacy and relevance and for analysing boundary work turns out to be helpful in describing in detail what happens in practice at the science–policy interface. In particular it helps to address the question of the way participants in the assessment process divide and co-ordinate work, how this shapes design elements and how this enhances credibility legitimacy and relevance of an assessment.  相似文献   

Linking vulnerability, adaptation, and resilience science to practice: Pathways, players, and partnerships   总被引：7，自引：1，他引：7  

Coleen Vogel  Susanne C. Moser  Roger E. Kasperson  Geoffrey D. Dabelko 《Global Environmental Change》2007,17(3-4):349-364

Vulnerability, adaptation and resilience are concepts that are finding increasing currency in several fields of research as well as in various policy and practitioner communities engaged in global environmental change science, climate change, sustainability science, disaster risk-reduction and famine interventions. As scientists and practitioners increasingly work together in this arena a number of questions are emerging: What is credible, salient and legitimate knowledge, how is this knowledge generated and how is it used in decision making? Drawing on important science in this field, and including a case study from southern Africa, we suggest an alternative mode of interaction to the usual one-way interaction between science and practice often used. In this alternative approach, different experts, risk-bearers, and local communities are involved and knowledge and practice is contested, co-produced and reflected upon. Despite some successes in the use and negotiation of such knowledge for ‘real’ world issues, a number of problems persist that require further investigation including the difficulties of developing consensus on the methodologies used by a range of stakeholders usually across a wide region (as the case study of southern Africa shows, particularly in determining and identifying vulnerable groups, sectors, and systems); slow delivery of products that could enhance resilience to change that reflects not only a lack of data, and need for scientific credibility, but also the time-consuming process of coming to a negotiated understanding in science–practice interactions and, finally, the need to clarify the role of ‘external’ agencies, stakeholders, and scientists at the outset of the dialogue process and subsequent interactions. Such factors, we argue, all hinder the use of vulnerability and resilience ‘knowledge’ that is being generated and will require much more detailed investigation by both producers and users of such knowledge.  相似文献   

基于偏振原理的水面反射光的剥离          下载免费PDF全文

周冠华  赵永超  耿修瑞  李小文 《水科学进展》2007,18(5):762-767

水面的镜面反射是影响水环境遥感的关键因素之一。通过分析气-水界面反射光的偏振特性,从多角度偏振遥感的角度,提出一种剥离水面反射光的方法,并通过室内实验进行了验证。将ASD光谱仪与线偏振片结合扩展成高光谱偏振传感器,获取不同观测天顶角时水面反射光的偏振光谱。结果表明,当探测角不满足布儒斯特角时,在偏振片的主消光方向能剥离绝大部分的水面反射光;当入射角越接近布儒斯特角,其剥离效果越佳;以布儒斯特角观测时,可以达到完全剥离的效果。即该方法能显著削弱、甚至完全剥离水面的反射光,直接获取离水辐亮度,对于提高水色遥感的精度有着重要的应用价值。  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   

元素地球化学场及其地学意义   总被引：6，自引：0，他引：6  

陈国能 《地球化学》1998,27(6):566-574

有关岩浆花岗岩成因的原地重熔说,揭示了各种化学元素在内生过程中的迁移规律。据此并结合元素在周期表中的位置,得出了元素地球化学场的概念,元素地球化学场不但总结了元素在原地重熔过程中的聚散趋势,而且揭示了元素自身组构与其空间分布规律的关系,展示出三个不同层次的地质断面,即花岗岩体上部和顶部盖层断面,大陆地壳断面及地球球体断面。  相似文献