中尺度降水集合预报随机参数扰动方法敏感性试验   总被引：6，自引：2，他引：4  

徐致真  陈静  王勇  李红祺  陈法敬  范宇恩 《气象学报》2019,77(5):849-868

中尺度降水模式预报具有很大的不确定性,为更好地描述与模式降水预报密切相关的物理过程关键参数的不确定性,基于中国气象局GRAPES（Global/Regional Assimilation and Prediction System）中尺度区域集合预报模式,从对模式降水预报不确定性有较大影响的积云对流、云微物理、边界层及近地面层等4个参数化方案中选取了18个关键参数,设计了一种随机参数扰动方案（Stochastically Perturbed Parameterization,SPP）,并通过2015年6—7月总计10 d的随机扰动集合预报试验,对比分析了SPP方案对不同物理过程参数扰动敏感性、随机场时、空尺度敏感性、能量变化特征及其集合预报效果。结果显示,对所选择的任一物理过程参数化方案增加SPP扰动后,降水及等压面要素的概率预报技巧优于无SPP扰动的预报,而扰动积云对流和边界层过程中的参数较扰动云微物理过程中的参数影响更显著,且同时扰动积云对流、云微物理、边界层及近地面层参数化方案中的18个参数的集合预报效果优于扰动任何单一物理过程中的部分参数,表明SPP方案能够有效地提高中尺度降水概率预报技巧;从能量变化特征可知,不同物理过程的参数扰动对动能、内能和总能量的影响层次和特征有所不同,但总体而言,扰动前后各项能量基本相同;随机场时、空尺度敏感性试验发现,SPP扰动随机场时间、空间相关尺度对集合预报效果有明显影响,当扰动随机场选用12 h抗相关时间及截断波数20时,集合预报结果最优。上述结果表明,SPP随机参数扰动方案不仅能够有效提高集合概率预报效果,还能够提高集合降水概率预报技巧,具有良好的业务应用与发展前景。   相似文献   

GRAPES区域集合预报两种侧边界扰动方法对比试验     

范宇恩  陈静  邓国  陈法敬  刘雪晴  徐致真 《气象》2019,45(12):1629-1641

中国气象局数值预报中心自2014年建立了区域集合预报业务系统,其使用的侧边界扰动由全球集合预报系统动力降尺度得到。为深入了解侧边界扰动对区域集合预报的影响,基于15 km水平分辨率的区域集合预报模式,使用动力降尺度方法和尺度化滞后平均法(scaled lagged average forecasting,SLAF)设计构造了两种侧边界扰动方案,并开展了2015年7月共6天的集合预报试验,利用集合均方根误差、集合离散度、连续分级概率评分、离群值、Brier Score及相对作用特征曲线面积等概率预报检验方法进行了多方面检验,分析了两种侧边界扰动方案对区域集合预报质量的影响。结果表明:动力降尺度侧边界扰动方案(DOWN)的扰动总能量在各垂直层次均大于SLAF方案,使得边界上前者的离散度大于后者,集合扰动增长更为合理;对于等压面要素和地面要素,DOWN方案的离散度、Outlier、CRPS等评分优于SLAF方案,反映了DOWN方案构造的侧边界扰动更加合理;在降水概率预报技巧方面,SLAF方案在评分上具有一定优势,但评分的提高没有通过显著性水平检验,因此认为两种方案对降水预报的改进基本相当。  相似文献   

Amino acids of the Murchison meteorite: II. Five carbon acyclic primary β-, γ-, and δ-amino alkanoic acids     

John R Cronin  Sandra Pizzarello  George U Yuen 《Geochimica et cosmochimica acta》1985,49(11):2259-2265

All ten of the possible five-carbon acyclic primary β-, γ-, and δ-amino alkanoic acids (amino position isomers of the valines) have been positively identified in hot-water extracts of the Murchison meteorite using combined gas chromatography-mass spectrometry (GC-MS) and ion exchange chromatography. With the exception of δ-aminovaleric acid, none of these amino acids has been previously reported to occur in meteorites or in any other natural material. The γ-amino acids (4-aminopentanoic acid, 4-aminc-2-meth-ylbutanoic acid, and 4-amino-3-methylbutanoic acid) are present at higher concentrations (about 5 nmol g^?1) than are the β-amino isomers (3-aminopentanoic acid, 3-amino-2-methylbutanoic acid, allo-3-amino-2-methylbutanoic acid, 3-amino-3-methylbutanoic acid, 3-amino-2-ethylpropanoic acid, and 3-amino-2,2-dimethylpropanoic acid) which are present at concentrations of 1–2 nmol g^?1. These amino acids are less abundant in the meteorite than either the corresponding α-amino acids or the four-carbon homologues. Thirty-six amino acids have now been positively identified in the Murchison meteorite, 17 of which are apparently unique to carbonaceous chondrites. The fact that the meteorite contains all possible five-carbon acyclic primary α-, β-, γ-, and δ-amino alkanoic acids is consistent with a synthetic process involving random combination of single-carbon precursors.  相似文献   

用间接浓度法测量干沉积通量   总被引：2，自引：1，他引：2  

袁撰英 《大气科学》1986,10(4):357-370

本文描述了用以测量干沉积通量的间接浓度法,推导并验证了估算沉积速度的阻力模式,评价了间接浓度法测量二氧化硫(SO_2)和臭氧(O_3)干沉积通量的误差. 结果表明,阻力模式能较准确地估算周平均沉积速度.用间接浓度法推算的O_3的周平均干沉积通量的份数误差为0.26,若配以日夜分离或稳定度分类采样,则误差将降至0.05;SO_2的份数误差只有0.15,但上述采样方法却不能减小其份数误差. 此外,O_3和SO_2的日间通量分别比其夜间通量大10倍和3倍.SO_2和O_3的沉积速度均有强烈的日周期变化,然而SO_2的日周期中,间有因地湿而畸变的现象.O_3浓度亦有一明显的日周期,且与它的沉积速度的日周期存在三小时的相位差.SO_2浓度则无明显日周期变化.  相似文献   

Slab weakening: Mechanical and thermal-mechanical consequences for slab detachment     

Shoichi  Yoshioka David A.  Yuen Tine B.  Larsen 《Island Arc》1995,4(2):89-103

Abstract Slab detachment is a geophysical instability whose manifestation can be revealed by seismic tomography. Evidence of this phenomenon is in the Dinarides/Hellenic and the New Hebrides subduction zones. Subducted slabs in these regions are torn horizontally at depths ranging from 100 to 300 km. We constructed a viscoelastic three-dimensional finite element model and investigated the state of stress. We found that an area with high stress concentration of the order of several hundred MPa is formed near the tip of the tear inside the slab, which can cause lateral migration of the tear. Favorable conditions for slab detachment are characterized by large interplate frictional force at a subduction zone and small slab resistance force deeper down. Stress concentration increases with the down-dip tension inside the slab. The phenomenon of slab weakening has also been studied from a thermal-mechanical standpoint, using a two-dimensional convection model with non-Newtonian, temperature-dependent rheology. The stress-dependent rheology plays an important role in causing local weakening of the descending slab. In strongly time-dependent situations the fast descending slab is not strong everywhere but has a weak region in the middle, making it vulnerable to slab detachment. The presence of viscous heating will enhance slab detachment tendency by further weakening the interior by the frictional heating. Besides these effects, there are other mechanisms which can also weaken the slab interior and help to make slabs more pliable and susceptible to detachment.  相似文献   

Application of saddlepoint approximation in reliability analysis of dynamic systems     

阮家荣  王家  区兆驹 《地震工程与工程振动(英文版)》2007,6(4):391-400

The application of the saddlepoint approximation to reliability analysis of dynamic systems is investigated. The failure event in reliability problems is formulated as the exceedance of a single performance variable over a prescribed threshold level. The saddlepoint approximation technique provides a choice to estimate the cumulative distribution function (CDF) of the performance variable. The failure probability is obtained as the value of the complement CDF at a specif ied threshold. The method requires computing the saddlepoint from a simple algebraic equation that depends on the cumulant generating function (CGF) of the performance variable. A method for calculating the saddlepoint using random samples of the performance variable is presented. The applicable region of the saddlepoint approximation is discussed in detail. A 10-story shear building model with white noise excitation illustrates the accuracy and effi ciency of the proposed methodology.  相似文献   

Interactive Web-Based Map: Applications to Large Data Sets in the Geosciences     

Zachary A. Garbow  Nicholas R. Olson  David A. Yuen  John M. Boggs 《Visual Geosciences》2001,6(3):1-14

Current advances in computer hardware, information technology and data collection techniques have produced very large data sets in a wide variety of scientific and engineering disciplines. We must harness this opportunity to visualize and extract useful information from geophysical and geological data. We have taken the task of data mining by implementing a map-like approach over a web server for interrogating the data, using a client-server paradigm. The spatial-data is mapped onto a two-dimensional grid from which the user (client) can quiz the data with the map-interface as a user extension. The data is stored on the server, while the computational gateway separating the client and the server can be the front-end of an electronic publication, electronic classroom, a survey, or an e-business. We have used a combination of Java, Java3D, and Perl for processing the data and communicating between the client and the server. The user can interrogate the geospatial data over any particular region with arbitrary dimensions and then receive back relevant statistical analysis, such as the histogram plots and local statistics. We have applied this method for the following data sets: (1.) distribution of prime numbers (2.) two-dimensional mantle convection (3.) three-dimensional mantle convection (4.) high-resolution satellite reflectance data over multiple wavelengths (5.) molecular dynamics describing the flow of blood in narrow vessels. Using the map-interface, one can actually interrogate this data over the Internet.  相似文献   

Shear deformation zones along major transform faults and subducting slabs   总被引：1，自引：0，他引：1  

D. A. Yuen  L. Fleitout  G. Schubert  C. Froidevaux 《Geophysical Journal International》1978,54(1):93-119

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An Approach to a Visual Language for Convective Fluid Flows: Visualization of Geophysical Simulations     

R. Zia  D. A. Yuen  T. A. Cortese  A. P. Vincent  S. Balachandar 《Visual Geosciences》1998,3(1):1-19

It was known that deep within numbers and binary data from simulations of geophysical convective flows resided various patterns. Two models of convective fluid flows were being considered. One was a model of two-dimensional (768 × 256) air convection with finite Prandtl number of one and Rayleigh number of 10⁸−10¹⁰, and another was a model of three-dimensional (up to 120 × 120 × 90) mantle convection with infinite Prandtl number and Rayleigh number of 10⁶−10⁸. Clearly, phenomena existed which superceded each individual dimensionless computer model to provide a piece of information regarding actual fluid flows. The problem was how to find, prove, and communicate these patterns and phenomena for convection simulations with gigabytes of data. In a search for such an analytical and communicative tool, the alternative of visualization was considered. The need for visualization was recognized and discussed. Then, utilizing both two- and three-dimensional models of high Rayleigh number convection, basic techniques of style and content were developed. Applications of the visualization techniques were designed utilizing IBM’s Data Explorer in order to create communicative images and movies, and after the applications, the problems of data storage and transfer became apparent. Throughout the process though, it became clear how important the language of vision actually could be in the geophysics community. In a field in which words such as plumes and internal waves have in ways replaced mathematics as the basic language for science, there is a need for another resource, another language-the visualization of convective fluid flows.  相似文献   

Post-Glacial Relaxation of A Viscously Stratified Compressible Mantle     

J. Wu  D. A. Yuen 《Geophysical Journal International》1991,104(2):331-349

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