基于标准差分析法的X波段双偏振天气雷达资料质量评估     

李思腾  仰美霖  李林  张舒婷  张治国  潘昱冰 《干旱气象》2019,37(3):467-476

2015年9月,北京市气象局在北京地区架设4部X波段双线偏振天气雷达并开展了观测试验。本文利用其中3部雷达在2016年6月30日的观测数据,用标准差分布统计方法,对雷达的观测参量进行初步质量评估。结果表明:(1)3部雷达反射率标准差符合理论值的数据占总观测数据的73.5%~77.9%,反射率的数据波动基本符合理论分布;(2)3部雷达差分反射率标准差符合理论值的数据占总观测数据的68.4%~81.4%,其中房山雷达数据波动较大;(3)3部雷达互相关系数标准差符合理论值的数据占总观测数据的45.7%~63.5%,其中房山雷达数据波动最大,其他2部雷达都有同程度的数据波动;(4)3部雷达差分传播相位标准差符合理论值的数据占总观测数据的73.5%~83.9%,其中房山雷达数据波动相对较大,与雷达其他观测参量相比,差分传播相位的波动较小。  相似文献   

一次冬季冰雹的双偏振多普勒天气雷达回波分析     

江慧远  魏鸣  张深寿  潘佳文  罗昌荣  林文 《气象科学》2019,39(6):755-762

为研究双偏振雷达资料在冬季冰雹监测预警中的应用,利用厦门S波段双偏振雷达资料,分析了2016年12月21日福建漳州冰雹的回波特征。发现在降雹过程中,最强回波达69 dBZ,三体散射回波径向长度达16 km,旁瓣回波切向宽达20 km,低层的钩状回波与入流缺口明显;冰雹区的差分反射率因子Z_(dr)和差分相位常数K_(dp)数值小,冰水混合区的相关系数ρ_(hv)较低。分析表明:此冰雹个例并非典型的超级单体,但存在超级单体的部分偏振回波特征,回波前侧下沉气流存在Z_(dr)弧,可延伸到中层,在入流缺口和后侧下沉气流处,Z_(dr)柱和K_(dp)柱成对出现,中层存在CC的低值环。  相似文献   

我国华南江南春季雷暴气候特征分析     

杨波  王园香  蔡雪薇 《热带气象学报》2019,35(4):470-479

基于我国华南江南地区274个基本地面气象观测站数据、全国闪电定位数据以及欧洲中心的全球大气再分析数据(ERA-Interim),对1981—2017年华南江南地区的春季雷暴日采用经验正交函数分解方法(EOF),并与气象要素场做回归分析。得出以下主要结论:(1)我国华南江南地区春季雷暴活动高发区主要在广西东部至广东西部;其高峰期在下午18:00和凌晨4:00左右,且大多数雷暴活动持续时间不超过3 h;山区雷暴活动主要在傍晚至夜间;平原雷暴活动主要在白天,高峰在17:00及06:00前后;(2)华南江南地区的雷暴活动存在着3~5年的短周期和16年左右的长周期变化;(3)雷暴日距平EOF分析的前3个主成分累计方差贡献达到72.3%。按其向量场的方差贡献分型,Ⅰ型表现为华南江南雷暴活跃特征呈现较统一的变化规律。深厚西南低涡槽前、上干下湿的水汽层结、上冷下暖的温度层结为华南江南地区发生大范围雷暴天气提供良好的动力、水汽和位势不稳定条件,是华南江南雷暴活跃异常的主要模态;Ⅱ型表现为从华南南部到江西与浙江南部有一条西南-东北向、下宽上窄的雷暴活跃正距平异常区,而两侧为负距平异常区。其环流特征表现为温度整层偏冷,水汽整层偏湿,而西南槽前动力抬升有利于水汽抬升凝结触发对流形成雷暴;Ⅲ型表现为华南和江南地区雷暴活跃特征呈南北反位相异常,其分界线在26 °N附近。其环流特征表现为较强的干冷空气南下与南方暖湿空气在南岭山区对峙形成异常的垂直环流圈。在其上升支,低层干冷空气被卷入中高层使得中高层暖湿空气凝结释放潜热形成对流,造成华南地区多雷暴发生,而江南地区处于垂直环流的下沉支,整层湿度偏干,造成江南地区雷暴相对偏少。   相似文献   

Limit states and failure mechanisms of viscous dampers and the implications for large earthquakes     

H. Kit Miyamoto  Amir S. J. Gilani  Akira Wada  Christopher Ariyaratana 《地震工程与结构动力学》2010,39(11):1279-1297

Fluid viscous dampers are used to control story drifts and member forces in structures during earthquake events. These elements provide satisfactory performance at the design‐level or maximum considered earthquake. However, buildings using fluid viscous dampers have not been subjected to very large earthquakes with intensities greater than the design and maximum considered events. Furthermore, an extensive database of viscous damper performance during large seismic events does not exist. To address these issues, a comprehensive analytical and experimental investigation was conducted to determine the performance of damped structures subjected to large earthquakes. A critical component of this research was the development and verification of a detailed viscous damper mathematical model that incorporates limit states. The development of this model and the laboratory and simulation results conclude good correlation with the new model and the damper limit states and provide superior results compared with the typical damper model when considering near collapse evaluation of structures. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Modeling three‐dimensional hydraulic fracture propagation using virtual multidimensional internal bonds     

K. Huang  Z. Zhang  Ahmad Ghassemi 《国际地质力学数值与分析法杂志》2013,37(13):2021-2038

Propagation of fractures, especially those emanating from wellbores and closed natural fractures, often involves Mode I and Mode II, and at times Mode III, posing significant challenges to its numerical simulation. When an embedded inclined fracture is subjected to compression, the fracture edge is constrained by the surrounding materials so that its true propagation pattern cannot be simulated by 2D models. In this article, a virtual multidimensional internal bond (VMIB) model is presented to simulate three‐dimensional (3D) fracture propagation. The VMIB model bridges the processes of macro fracture and micro bond rupture. The macro 3D constitutive relation in VMIB is derived from the 1D bond in the micro scale and is implemented in a 3D finite element method. To represent the contact and friction between fracture surfaces, a 3D element partition method is employed. The model is applied to simulate fracture propagation and coalescence in typical laboratory experiments and is used to analyze the propagation of an embedded fracture. Simulation results for single and multiple fractures illustrate 3D features of the tensile and compressive fracture propagation, especially the propagation of a Mode III fracture. The results match well with the experimental observation, suggesting that the presented method can capture the main features of 3D fracture propagation and coalescence. Moreover, by developing an algorithm for applying pressure on the fracture surfaces, propagation of a natural fracture is also simulated. The result illustrates an interesting and important phenomenon of Mode III fracture propagation, namely the fracture front segmentation. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

When do we need a trend model in kriging?   总被引：1，自引：0，他引：1  

A. G. Journel  M. E. Rossi 《Mathematical Geology》1989,21(7):715-739

Under usual estimation practice with local search windows for data and for interpolation situations, universal kriging and ordinary kriging yield the same estimates, using a data set with apparent trend, for both the unknown attribute and its trend component. Modeling the trend matters only in extrapolation situations. Because conditions of the case study presented arise most frequently in practice, the simpler ordinary kriging is the preferred option.  相似文献   

Theoretical background for the inversion of seismic waveforms including elasticity and attenuation   总被引：3，自引：0，他引：3  

Albert Tarantola 《Pure and Applied Geophysics》1988,128(1-2):365-399

To account for elastic and attenuating effects in the elastic wave equation, the stress-strain relationship can be defined through a general, anisotropic, causal relaxation function ^ijkl (x, ). Then, the wave equation operator is not necessarily symmetric (self-adjoint), but the reciprocity property is still satisfied. The representation theorem contains a term proportional to the history of strain. The dual problem consists of solving the wave equation withfinal time conditions and an anti-causal relaxation function. The problem of interpretation of seismic waveforms can be set as the nonlinear inverse problem of estimating the matter density (x) and all the functions ^ijkl (x, ). This inverse problem can be solved using iterative gradient methods, each iteration consisting of the propagation of the actual source in the current medium, with causal attenuation, the propagation of the residuals—acting as if they were sources—backwards in time, with anti-causal attenuation, and the correlation of the two wavefields thus obtained.  相似文献   

行业空间配置的线性对偶模式     

梁进社 《地理学报》1994,49(2):128-138

本文研究诸如钢铁、有色金属、基本化工等一类行业的空间配置。由于韦勃、廖施的理论的一些前提条件在这里不存在，使得他们的研究方法显得十分不足。本文作者建立了具有对偶的线性规划模式来解决这类行业的空间配置。这一对模式的解给出了具有最小行业总成本的配置方案和与之相应的产品和原料在各个区位的影子价格。尤其是作者依据空间价格均衡找出了原模式与对偶模式的解之间的关系，这些关系是行业空间配置优化的效率条件。  相似文献   

Surface-wave mode coupling for efficient forward modelling and inversion of body-wave phases     

Henk Marquering  Roel Snieder 《Geophysical Journal International》1995,120(1):186-208

  相似文献   

IMPLICIT NONLINEAR NORMAL MODE INITIALIZATION:A MULTIGRID APPROACH          下载免费PDF全文

D.R.C.Nair  B.Chakravarty  P.Niyogi 《Acta Meteorologica Sinica》1993,(1)

The implicit nonlinear normal mode initialization (INMI) is applied to a tropical limited area shallow water modelin spherical coordinates.The boundary condition for the INMI scheme is based on the boundary formulation of themodel.The INMI scheme is found to be very efficient in suppressing spurious gravity wave oscillation and providing awell balanced initial data set for the model.The INMI scheme involves solving a number of elliptic type equations withvarying complexity.and hence an efficient numerical technique is required for solving such equations.In order to makeINMI computationally more attractive,we are employing the multigrid method for solving all the elliptic type equationsin the INMI scheme.The numerical procedures for the development of such multigrid solvers are briefly described.  相似文献