竖向质量分布对框架结构动力特性影响的研究

在框架结构动力分析中,往往是把填充墙质量集中在楼层处进行求解.文中考虑填充墙实际分布对结构自振特性的影响,通过传递矩阵法求解结构自振频率和振型,并进一步分析了高阶频率的分布规律.结果表明,与采用集中质量模型的振型叠加法相比,填充墙的竖向质量分布会对框架结构高阶频率产生很大影响;框架结构的高阶模态具有局部性和密集分组的特...     

TSAnalysis软件在辽宁地区面波频散提取中的应用

介绍了在辽宁地区使用基于图像分析的双台相速度频散曲线提取方法进行相速度频散提取的工作,并选取了TSAnalysis软件操作实例详细展示提取过程。通过质量控制和筛选,获得了15~120s周期范围内的1100条独立双台路径相速度频散资料。     

印度洋海啸引起的防震思考——一个退休的老地质工作者的思考

2004年12月26日发生在印尼苏门答腊岛北端附近海域的里氏8.9级地震,引发了一场波及印度洋沿岸多个国家的大海啸,造成了一次空前的世界性灾难.倾刻之间,高达数十米的巨浪扑向印尼、斯里兰卡、印度南部、泰国、马尔代夫等国的海岸,近30万人丧生,伤者数十万,数百万人流离失所,全世界上百个国家,上万个家庭从圣诞节的欢乐中顿时堕人悲痛的渊薮.一个多月过去了,不仅受灾国家,全世界人民的心,依然处在巨大的震惊、恐惧和悲痛的阴影中.     

The subduction of the west Pacific plate and the destruction of the North China Craton

While a general concensus has recently been reached as to the causal relationship between the subduction of the west Pacific plate and the destruction of the North China Craton, a number of important questions remain to answer, including the initial subduction of west Pacific plate beneath the eastern Asian continent, the position of west Pacific subduction zone during the peak period of decratonization(i.e., Early Cretaceous), the formation age of the big mantle wedge under eastern Asia, and the fate of the subducted Pacific slab. Integration of available data suggests that the subduction of the western Pacific plate was initiated as early as Early Jurrasic and the subduction zone was situated to 2,200 km west of the present-day trench in the Early Creataceous, as a result of eastward migration of the Asian continent over a distance of ca. 900 km since the Early Cretaceous.The retreat of the subducting west Pacific plate started ～145 Ma ago, corresponding to the initial formation of the big mantle wedge system in the Early Cretaceous. The subduction of the Pacific slab excerted severe influence on the North China Craton most likely through material and energy echange between the big mantle wedge and overlying cratonic lithosphere. The evolution history of the west Pacific plate was reconstructed based on tectonic events. This allows to propose that the causes of phases A and B for the Yanshanian orogeny were respectively related to rapid low-angle subduction and to lowering subduction angle of the west Pacific plate. At ca. 130–120 Ma, the subduction of the west Pacific plate was characterized by increasing subducting angle, slab rollback and rapid trench retreat, leading to the final stagnation of the subducting slab within the mantle transition zone. This process may have significantly affected the physical property and viscosity of the mantle wedge above the stagnant slab, resulting in non-steady mantle flows. The ingression of slab-released melts/fluids would significantly lower the viscosity of the mantle wedge and overlying lithosphere, inducing decratonization. This study yields important bearings on the relationship between the subduction of the west Pacific plate and the evolution of the lithospheric mantle beneath the North China Craton.     

2005年6月桂南沿海降水异常偏多成因分析

2005年6月桂南沿海降水异常偏多,通过分析气候背景,环流形势特征,并将其与历史多雨年和少雨年做对比分析得出:2005年6月桂南沿海降水偏多是在多雨的大气候变化周期中发生的;西太平洋副热带高压强度偏强、西伸脊点位置偏西、脊线位置偏南是2005年6月桂南沿海降水异常偏多的主要原因.     

Modelling the sensitivity of wheat growth and water balance to climate change in Southeast Australia

A simulation study was carried out to assess the potential sensitivity of wheat growth and water balance components to likely climate change scenarios at Wagga Wagga, NSW, Australia. Specific processes considered include crop development, growth rate, grain yield, water use efficiency, evapotranspiration, runoff and deep drainage. Individual impacts of changes in temperature, rainfall and CO₂ concentration ([CO₂]) and the combined impacts of these three variables were analysed for 2050 ([CO₂] = 570 ppm, T +2.3°C, P ?7%) and 2070 ([CO₂] = 720 ppm, T +3.8°C, P ?10%) conditions. Two different rainfall change scenarios (changes in rainfall intensity or rainfall frequency) were used to modify historical rainfall data. The Agricultural Production Systems Simulator (APSIM) was used to simulate the growth and water balance processes for a 117 year period of baseline, 2050 and 2070 climatic conditions. The results showed that wheat yield reduction caused by 1°C increase in temperature and 10% decrease in rainfall could be compensated by a 266 ppm increase in [CO₂] assuming no interactions between the individual effects. Temperature increase had little impact on long-term average water balance, while [CO₂] increase reduced evapotranspiration and increased deep drainage. Length of the growing season of wheat decreased 22 days in 2050 and 35 days in 2070 conditions as a consequence of 2.3°C and 3.8°C increase in temperature respectively. Yield in 2050 was approximately 1% higher than the simulated baseline yield of 4,462 kg ha^???1, but it was 6% lower in 2070. An early maturing cultivar (Hartog) was more sensitive in terms of yield response to temperature increase, while a mid-maturing cultivar (Janz) was more sensitive to rainfall reduction. Janz could benefit more from increase in CO₂ concentration. Rainfall reduction across all rainfall events would have a greater negative impact on wheat yield and WUE than if only smaller rainfall events reduced in magnitude, even given the same total decrease in annual rainfall. The greater the reduction in rainfall, the larger was the difference. The increase in temperature increased the difference of impact between the two rainfall change scenarios while increase in [CO₂] reduced the difference.     

南海海岛自动气象站防护应用技术探索

立足海南及南海的自然条件,结合海岛自动气象站在南海高温、高湿、高盐雾、强辐射、强风等恶劣气候环境下使用情况,通过对历年来海岛自动气象站故障及失效模式的统计和分析,总结分析故障原因。根据设备维护人员多年气象设备保障工作积累总结的经验,从海岛自动气象站结构和防护要求出发,集成应用市场上优质材料、先进工艺和多种成熟、关键设备防护技术,形成一些气象设备防护的有效方法措施,以提高海岛自动气象站对海洋环境的适应性和性能,延长设备使用寿命。     

基于对流可分辨集合预报的阜宁龙卷概率预报研究

本文针对2016年6月23日江苏阜宁龙卷,设计了两组对流可分辨尺度集合预报:一组以ERA5再分析资料为初始和侧边界(CEFS_ERA5);另一组以NCEP GEFS为初始和侧边界(CEFS_GEFS),评估了两组试验对此次龙卷的预报能力。结果显示:两组对流尺度集合预报均有约半数以上成员能够再现龙卷超级单体的特征;2~5 km上升螺旋度(UH25)对本次龙卷超级单体有较好的预报指示意义。在上述分析的基础上,考虑位置预报偏差,提出了一种基于UH25的邻域龙卷概率预报产品,分析了龙卷概率预报技巧对关键参数邻域半径和UH25阈值的敏感性,CEFS_ERA5邻域半径取15个格点,UH25阈值取250 m²·s^-2最优;而CEFS_GEFS邻域半径取15个格点,UH25阈值取100 m²·s^-2最优。总的来说,邻域概率预报产品显著提升了对此次龙卷概率预报水平。     

云宵县5月暴雨客观预报模型

采用文献[1]提出的技术模型，研制了云宵县5月暴雨预报方法，建立了4个因子结构简单而天气学意义明了的客观预报模型。经2000～2003年试用，这种基于场量因子的预报模型，未漏报，严格评定的准确率为67％，明显优于主观预报。     

RegCM4中陆面过程参数化方案对东亚区域气候模拟的影响

利用区域气候模式RegCM4.0分别选取其陆面参数化方案CLM3.5与BATS1e,针对东亚地区进行约44 a(1957-2001年)的模拟试验(分别取名为R-CLM与R-BATS),以研究陆面过程参数化方案对区域气候模拟的影响.结果表明,R-CLM地表气温比R-BATS平均高3.6℃,均方根误差比R-BATS约减少44％,其中,以中国华南、西北等地区的偏高改进最为明显;降水平均减少0.17 mm/d,均方根误差约减少6.9％,其中,在中国华南、东北等东部地区误差减少最多;表层10 cm土壤湿度平均增加0.008 m3/m3,并在中国东北等中高纬度地区偏大最为明显.分析表明,R-CLM模拟的土壤湿度在中高纬度地区比R-BATS偏高是由于其蒸散与地表径流较少使得陆地水储量相对较高所致,因而该地区的产流机制仍需改进以改善其土壤湿度模拟;R-CLM的地表气温模拟普遍较高主要是由于其陆表吸收辐射量模拟较高潜热通量模拟较弱所致;另外,R-CLM中较弱的蒸散与较高的地表气温引起了大气环流场的改变,导致R-CLM在模拟区尤其是中国东部地区模拟的垂向及水平水汽输送较弱,大气可降水量较少,因而在中国华南、东北等大部分地区降水相对偏少,并在一定程度上增加了到达地表的辐射量,进而影响其地表气温模拟.