1891—1990年期间北半球大气环流和中国气候的变化   总被引：23，自引：4，他引：23       下载免费PDF全文

章基嘉  高学杰 《应用气象学报》1994,5(1):1-10

根据1891–1990年北半球大气环流型W、C、E年频数以及全国平均年温、北京和上海的年温的时间序列，计算分析了它们各自的主值函数、功率谱和凝聚谱，得到了环流和温度的百年长期趋势、周期谱图和它们之间的凝聚关系，并用距平累加曲线法，相邻两阶段的信噪比法，揭示了环流和温度在近百年变化过程中的转折和突变。最后，用Mann-Kendall法对它们作了检验。讨论了环流异常与气候异常的关联性，并给予一定的解释。  相似文献   

地球表层系统非线性演化模式   总被引：9，自引：0，他引：9       下载免费PDF全文

陈之荣 《地球物理学报》1987,30(4):389-398

本文运用结构、功能和历史相结合的系统方法,研究地球表层系统的环境、演化分期及各演化期的形成,提出一个强调突变在演化中起重大作用的地球表层系统非线性演化模式。  相似文献   

全球环境变化与综合灾害风险防范研究   总被引：10，自引：1，他引：9  

史培军  李宁  叶谦  董文杰  韩国义  方伟华 《地球科学进展》2009,24(4):428-435

实现可持续发展,需要加深理解全球环境变化对可更新资源保障能力和灾害发生频率、强度和时空格局的影响。近年来发生在世界各国的巨灾造成了严重的灾情,如2008年中国南方的冰冻雨雪灾害,2007年孟加拉国的台风灾害,2005年的美国卡特里娜飓风等。加强对全球环境变化背景下的综合灾害风险防范研究已成为一个迫切需要解决的可持续发展问题。为此,在CNC IHDP的领导下,CNC IHDP RG工作组向IHDP提出了开展全球环境变化与综合风险防范研究的建议。经过2年多的努力,作为IHDP新一轮国际性核心科学计划——综合风险防范（IHDP IRG）已经得到IHDP SC的认可,即将于2009年4月在德国波恩IHDP科学大会期间正式宣布启动。该核心计划为从事风险研究、管理和具体实践方面的全球顶级专家和组织搭建交流平台,并引导未来国际综合风险防范研究从综合灾害风险防范的科学、技术与管理问题入手,通过案例对比,从多学科角度,对综合灾害风险防范的理论和方法进行创新性研究,以推动全球综合减灾实践的深入发展。CNC IHDP RG作为这一核心科学计划的倡议、发起和主要组织者,通过该计划的成功实施,不但可以在国际上充分展现我国综合灾害风险研究领域的成果,更将有助于大幅度提升中国在全球环境变化研究中的国际地位。  相似文献   

岩体应力应变曲线转型的孔压效应与降雨滑坡的机制分析   总被引：2，自引：0，他引：2  

杨继红  董金玉  郝小红  刘汉东  刘海宁 《工程地质学报》2009,17(5):662-665

从宏观与微观机制方面探讨了孔隙水压力对岩体脆－延性转变的影响。定义了一个峰后破坏割线模量Epost来表征孔隙水压力对岩体应力应变曲线转型的效应,并结合突变理论得到的斜坡失稳的刚度判据,进一步分析了孔隙水压力对应力应变曲线峰后斜率的影响,随孔隙水压力的增加,峰后曲线斜率变陡,峰后刚度增大,即材料的均匀性、脆性增大与刚度比k减小。因此在系统内部条件不变时,刚度比k=1时就存在一个临界孔隙水压力pwcritical,即降雨等涨落因素引起滑面介质中的孔隙水压力大于这个临界值时斜坡就易于发生突变失稳。从而深化认识了降雨等外部涨落因素对斜坡系统失稳的重要触发作用。  相似文献   

热带气旋运动曲率的数学模型与路径异常的月尖突变判据   总被引：7，自引：2，他引：7       下载免费PDF全文

徐祥德  解以扬 《热带气象学报》1993,9(4):308-316

采用运动曲率数学模型，研究热带气旋异常路径的成因，得到的主要结果是：热带气旋路径曲率及其变化与科氏力参数、环境场气压分布、热带气旋的移速及涡旋动力结构、下垫面摩擦力等因子有关；当各类影响因子渐变至满足月尖突变判据时，出现演变曲线的折叠区，随着外源参数变化，一旦解移出折叠区，热带气旋便可发生移间突变，出现各类异常轨迹。  相似文献   

非静力平衡大气非线性层结对称运动的稳定性和突变          下载免费PDF全文

罗德海  彭晓林 《气象学报》1993,51(4):414-424

在假定了环境地转风具有水平和垂直的线性切变的情况下,考虑大气层结的线性和非线性切变的作用,建立了一个非线性常微分方程组,然后构造了一个Hamilton函数,通过讨论Hamilton函数的凸凹性,得到了非线性层结对称运动的不稳定判据,同时讨论了非线性层结对称运动产生突变的条件。  相似文献   

土质滑坡体破坏的突变模型   总被引：15，自引：0，他引：15  

高鹏  艾南山 《工程地质学报》1994,2(4):67-76

本文运用突变理论，分析了土质坡体破坏的两种方式:突变式破坏和渐变式破坏，建立了相应的在突变模型，从理论上解释了高速滑坡与低速滑坡的产生根源。对于受水文条件诱发的滑坡，提出了相应的判别准则。  相似文献   

浙江省1901—2017年降水序列构建及变化特征分析     

肖晶晶  李正泉  郭芬芬  姚益平  马浩  王阔  温泉沛 《气候变化研究进展》2018,14(6):553-561

基于通过均一性检验的历史观测资料和GPCC格点降水数据,采用逐步回归方法,构建了可以代表浙江省的1901—2017年年降水序列,并通过Morlet小波分析、MK检验、气候趋势等分析了浙江百年降水变化特征。结果表明：浙江68个台站1951—2017年月降水序列数据质量较好,均通过RHtest均一性检验。交叉检验表明,采用逐步回归方法区别台站资料长度建立的最优拟合方程组,能很好地反演浙江68个台站1901—2013年年降水情况。1901—2017年浙江省年降水量无明显线性变化趋势,但存在56 a和35 a两个变化主周期,在1960年前后全省降水由多雨期向少雨期突变。1901—2017年浙江降水气候倾向率呈东北高西南低的分布特征,各地数值分布在-15.6~19.1 mm/10a之间;平均相对变率呈北低南高的分布特征,各地数值分布在11.1%~20.2%之间。  相似文献   

On the ignition of geostrophically rotating turbidity currents     

Emms 《Sedimentology》1999,46(6):1049-1063

Two models of a geostrophically rotating turbidity current are examined to compare predictions for ignition with the catastrophic state. Both models describe the current as a tube of sediment-laden water traversing along and down a uniform slope. The first (four-equation) model neglects the energy required to lift the sediment from the seabed into suspension. The second (five-equation) model rectifies this shortcoming by introducing a turbulent kinetic energy equation and coupling the bottom stress to turbulence in the plume. These models can be used to predict the ignition, path and sediment deposition of a geostrophically rotating turbidity current. The criteria for ignition in the four-equation model can be described by a surface in three-dimensional phase space (for a non-entraining current). This surface lies near the geostrophic equilibrium state. For a turbidity current occurring in the Greenland Sea, velocities above 0·053 m s^–1 or volumetric concentrations of sediment above 2·7 × 10^–5 lead to ignition. In general, if the tube is started pointing downslope, then ignition is more likely than if it is initially directed alongslope. However, there exists a set of initial conditions in which the current ignites if started along or downslope, but deposits if started at an intermediate angle. The five-equation model requires a larger initial velocity (greater than 1·6 m s^–1) to ignite than does the four-equation model. Ignition is determined qualitatively by the geostrophic state and the initial normal Froude number. Solutions show a tendency to travel further alongslope during ignition, reflecting the restriction that the energy budget places on the sediment load. A qualitative difference to phase space in the five-equation model is the existence of a region in which the tube has insufficient energy to support the sediment. Turbulence dies rapidly in this region, and so the sediment is deposited almost immediately.  相似文献   

Soil fertility self-development under ecological restoration in the Zhuxi watershed in the red soil hilly region of China     

Li-yue Bai  Zhi-qiang Chen  Zhi-biao Chen 《山地科学学报》2014,11(5):1231-1241

Current methods that utilize simple data or models to judge whether soil fertility can selfdevelop are not sufficiently rigorous. A new framework has been set up using catastrophe theory, laboratory experiment, field work, and 3S(Geographic information system, Global positioning system, and Remote sensing) to explore soil fertility catastrophe under ecological restoration, discriminate whether soil fertility can self-develop, and propose adjustment of ecological restoration measures in the Zhuxi watershed of Changting County, Fujian Province, China, which is a typical representative of the red soil hilly region of China. The results show that: 1) the soil fertility is obviously improved through the four ecological restoration measures, which impels soil fertility catastrophe. Among 89 soil samples, catastrophic soil samples and stable soil samples account for 26(29.21%) and 63(70.79%) of the samples, respectively. The four ecological restoration measures are listed in the order lowquality forest improvement arbor–bush–herb mixed plantation orchard improvement closing measures according to the proportions of catastrophic soil samples. A typical soil sample in Bashilihe that can self-develop is selected as the criterion to judge the upper lobe and lower lobe of soil fertility in the process surface of the Cusp catastrophe model. Twenty-six(29.21%) were in the middle lobe, 10(11.24%) were in the upper lobe, and 53(70.79%) were in the lower lobe. The catastrophic direction of 26 catastrophic soil samples is to the upper lobe according to soil and water loss change as well as fieldwork. There is a significant positive correlation of Δ with soil and water loss change, and the lower soil and water loss relates to higher catastrophic probability. 2) Soil fertility self-development could be regionalized as "Soil fertility can self-develop" whose area was 12.74 km2(28.33%) distributed mainly in the leftmost and rightmost parts, "Soil fertility tends to self-develop" whose area was 11.63 km2(25.89%) distributed mainly in the middle part, and "Soil fertility cannot self-develop" whose area was 20.58 km2(45.78%) distributed mainly between the above two types. 3) There is no need to take ecological restoration measures and excessive human interference should be avoided in the future in regions of "Soil fertility can self-develop" and "Soil fertility tends to self-develop," and ecological restoration measures should be taken in region of "Soil fertility cannot self-develop." 4) We suggest withdrawal and implementation of ecological restoration measures should be incorporated into the evaluation criteria of ecological restoration to avoid misuse of funds.  相似文献