一次西南低涡过程的地面场中尺度分析     

曾俊  卢敬华  潘鄂芬 《成都信息工程学院学报》1990,(Z1)

本文运用带通滤波分析方法,对四川省1981年7月由西南低涡等天气系统引起的大暴雨过程作了地面气象要素场的中尺度诊断分析。结果表明,带通滤波后的场具有明显的中尺度特征,其中一些物理量场的适当配置与6小时后的暴雨中心有较好的对应关系。说明了此带通滤波方法在实际业务预报中具有一定的使用价值。  相似文献   

利用自回归模型检测地球极移重力效应     

杨学峰  孙和平  徐建桥 《大地测量与地球动力学》2004,24(2):110-114

同时采用4个台站的国际超导重力仪长期连续重力观测资料和国际地球自转服务中心提供的同步地球自转参数，研究了极移引起的地球重力场变化特征。利用自回归模型估计了各序列的功率谱密度和积谱密度，结果表明极移导致的重力效应的主要能量集中在Chandler摆动和周年项附近，叠积后实际重力观测与极移重力信号理论值之间的差异分别为0．4％和3．9％，说明超导重力仪可有效监测极移导致的重力变化。  相似文献   

多条太阳光球FeI线在磁场中形成及形成深度的综合分析(Ⅰ)     

宋慰鸿  艾国祥  张洪起  李孝昌 《中国天文和天体物理学报》1990,(1)

针对多通道滤光器太阳磁场望远镜的磁场观测定标及掌握(所采用的)谱线特征之需要,取VAL宁静太阳大气模型计算了7条Fel光球线的Stokes轮廓、形成深度、贡献函数分布,从而较为系统地对多条反常及正常Zeeman线的特征及性质作出了分析与总结,解释了在磁光效应影响下Stokes Q,U参量的形成深度曲线在近线心区域处出现陡峭峰值的原因。  相似文献   

Modelling Gas And Dust Release From Comet Hale–Bopp     

Prialnik  D. 《Earth, Moon, and Planets》1997,77(3):223-230

Numerical simulations of the evolving activity of comet Hale-Bopp are presented, assuming a porous, spherical nucleus, 20 km in radius, made of dust and gas-laden amorphous ice. The main effects included are: crystallization of amorphous ice and release of occluded gas, condensation, sublimation and flow of gases through the pores, changing pore sizes, and flow of dust grains. The model parameters, such as initial pore size and porosity, emissivity, dust grain size, are varied in order to match the observed activity. In all cases, a sharp rise in the activity of the nucleus occurs at a large heliocentric distance pre-perihelion, marked by a few orders of magnitude increase in the CO and the CO₂ fluxes and in the rate of dust emission. This is due to the onset of crystallization, advancing down to a few meters below the surface, accompanied by release of the trapped gases. A period of sustained, but variable, activity ensues. The emission of water molecules is found to surpass that of CO at a heliocentric distance of 3 AU. Thereafter the activity is largely determined by the behaviour of the dust. If a dust mantle is allowed to build up, the water production rate does not increase dramatically towards perihelion; if most of the dust is ejected, the surface activity increases rapidly, producing a very bright comet. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

台湾海峡西岸重力场变化梯度场图像分析     

梁全强  刘序俨  黄声明  吴维日  陈新泽 《大地测量与地球动力学》2006,26(4):82-85

讨论了应用曲面拟合技术和利用离散的重力观测点的重力变化对特定研究区的重力场变化进行数值模拟以获取该区重力变化空间梯度场图像的具体方法;并应用该方法获得了2004年3月福建安溪3.6级地震前的重力变化空间梯度场图像,发现空间梯度场图像能清晰地反映出地震前重力场群体性变化的差异性;利用此方法对2005年6月~2006年3月间台湾海峡西岸重力场变化进行数值模拟,获得其空间梯度场图像。  相似文献   

NGC 1883: a neglected intermediate-age open cluster located in the outskirts of the Galactic disc     

Giovanni Carraro  Gustavo Baume  Sandro Villanova 《Monthly notices of the Royal Astronomical Society》2003,343(2):547-551

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Correcting systematic effects in a large set of photometric light curves     

O. Tamuz  T. Mazeh  S. Zucker † 《Monthly notices of the Royal Astronomical Society》2005,356(4):1466-1470

We suggest a new algorithm to remove systematic effects in a large set of light curves obtained by a photometric survey. The algorithm can remove systematic effects, such as those associated with atmospheric extinction, detector efficiency, or point spread function changes over the detector. The algorithm works without any prior knowledge of the effects, as long as they linearly appear in many stars of the sample. The approach, which was originally developed to remove atmospheric extinction effects, is based on a lower rank approximation of matrices, an approach which has already been suggested and used in chemometrics, for example. The proposed algorithm is especially useful in cases where the uncertainties of the measurements are unequal. For equal uncertainties, the algorithm reduces to the Principal Component Analysis (PCA) algorithm. We present a simulation to demonstrate the effectiveness of the proposed algorithm and we point out its potential, in the search for transit candidates in particular.  相似文献   

The evolution of binary fractions in globular clusters     

N. Ivanova  K. Belczynski  J. M. Fregeau  F. A. Rasio 《Monthly notices of the Royal Astronomical Society》2005,358(2):572-584

We study the evolution of binary stars in globular clusters using a new Monte Carlo approach combining a population synthesis code ( startrack ) and a simple treatment of dynamical interactions in the dense cluster core using a new tool for computing three- and four-body interactions ( fewbody ). We find that the combination of stellar evolution and dynamical interactions (binary–single and binary–binary) leads to a rapid depletion of the binary population in the cluster core. The maximum binary fraction today in the core of a typical dense cluster such as 47 Tuc, assuming an initial binary fraction of 100 per cent, is only ∼ 5–10 per cent. We show that this is in good agreement with recent Hubble Space Telescope observations of close binaries in the core of 47 Tuc, provided that a realistic distribution of binary periods is used to interpret the results. Our findings also have important consequences for the dynamical modelling of globular clusters, suggesting that 'realistic models' should incorporate much larger initial binary fractions than has usually been the case in the past.  相似文献   

Atmospheric radiative transfer simulation for atmospheric correction of remote sensing data     

Yunfei Bao Shengbo Chen 《东北亚地学研究》2006,9(1):100-108

IntroductionThe radiance leaving the earth-atmosphere sys-tem which can be sensed by a satellite borne ra-diometer is the sum of radiation emission fromtheearth surface and each atmospheric level that aretransmittedtothe top of the atmosphere.The radia-tion emissionfromthe earthsurface andthe radianceof each atmospheric level can be separated fromtheradiance at the top the atmospheric level a satellitemeasured.Thus,the earth surface parameters willbe retrieved from the surface radiance after a…  相似文献   

The Faint Sky Variability Survey – I. Goals and data reduction process     

P. J. Groot  P. M. Vreeswijk  M. E. Huber  M. E. Everett  S. B. Howell  G. Nelemans  J. van Paradijs  E. P. J. van den Heuvel  T. Augusteijn  E. Kuulkers  R. G. M. Rutten  J. Storm 《Monthly notices of the Royal Astronomical Society》2003,339(2):427-434

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