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1.
大气角动量资料源的变化对研究日长变化激发的贡献 总被引：4，自引：0，他引：4
本文采用1979—1995年间由空间大地测量技术观测和归算的日长变化（△LOD）序列,以及由美国国家气象中心（NMC）和美国国家环境预测中心与美国国家大气研究中心（NCEP／NCAR）利用全球气象资料各自归算的大气角动量（AAM）序列,重新分析、研究和估计了大气对△LOD的激发作用,比较了上述各个大气角动量序列对△LOD激发贡献,得到的主要结果如下：1．NCEP／NCAR用同化后的全球气象资料重新归算的AAM序列比原来NMC的序列具有系统均匀化、噪声小和分辨率高的特点,以及和日长变化的符合度更好．2．采用NCEP／NCAR重新归算的AAM来研究大气在从亚季节性到年际时间尺度上对非潮汐△LOD的激发贡献,得到进一步改善的结果,尤其是在准两年时间尺度上．但是大气仍不能解释全部△LOD化,可能存在其它激发源．3．大气对△LOD高频潮汐项的估计值影响较小,并从△LOD中解算出周年和半年潮汐参数估计的初步结果． 相似文献
2.
不同频段上极移,日长变化与大气角动量变化激发结果的比较 总被引：1，自引：0，他引：1
本文用ＪＭＡ大气角动量序列计算了对极移和日长变化的激发量（ｍ＇１、ｍ＇２和ｍ＇３），并分三个频段与天文观测得到的地球自转参数序列（ｍ１、ｍ２和ｍ３）进行了比较．结果表明：在钱德勒和季节性频段上，大气运动确实是固体地球自转变化的主要激发源． 相似文献
3.
日长、大气角动量和太阳活动指数中MJO的子波变换分析 总被引：2，自引：0，他引：2
顾震年 《中国科学院上海天文台年刊》1995,(16):21-26
本文描述了子波变换分析的基本原理，并用这一方法分析了日长、大气角动量和太阳活动指数的MJO特性。结果表明：几种序列均存在着40－60天高频变化，且这些变化在不同历元处有显著的差别，这些时空变化特性将进一步揭示太阳活动指数与日长、大气之间的相互关系。作者认为，子波变换分析可帮助我们考虑这些序列之间的动力学机制。 相似文献
4.
大气对地球自转季节性变化的贡献 总被引：2，自引：0，他引：2
采用１９７９－１９９５年期间新的大气角动量资料,研究了大气在季节性时间尺度上对日长变化和极移的贡献。结果表明,考虑了风和大气压的贡献后,大气在周年和半年时间尺度上对日长变化的贡献分别可达９５％和８８％。同时还给出了大气对极移激发的定量结果,其中,大气的周年尺度上对极移Ｘ分同的贡献为１６％,对Ｙ分量的贡献为４３％;在半年尺度上海洋的贡献,才能进上步解决地球自转激发的问题。 相似文献
5.
大气相对固体地球的运动产生大气相对角动量，它的变化可以激发地球自转多时间尺度的变化．计算大气相对角动量现在采用两种不同的垂直积分高度，一种为从地形表面积分到顶层大气，称之为SP方法；另一种为从1000hPa积分到顶层大气，称之为BP方法，对采用这两种方法所得到的大气相对角动量进行了详细的比较．应用欧洲中距气象预报中心（ECMWF）和美国国家环境预报中心（NCEP）大气再分析数据，重新研究了大气相对角动量变化的时空特征．通过对大气相对角动量季节平均，季节振幅和时空特征的分析，得出ECMWF和NCEP的大气相对角动量变化对地球自转周年极移的影响，在亚洲季风区域和南极洲区域差别最为明显． 相似文献
6.
地球自转、大气角动量和太阳活动的30—60天波动特征 总被引：1，自引：0，他引：1
本分析了十三年的日长变化、大气角动量和太阳黑子相对数资料，研究了这三种资料序列中30－60天波动过程，用统计分析和检验方法证实这种波动过程在时间尺度上具有随机游动的特性，定量分析表明，在此时间尺度上，大气环流中带风的作用对日长变化的贡献约为87％。如果太阳活动对地球自转中30－60天波动存在激发作用，其作用过程不能完全证明是直接通过大气影响地球自转的。可能存在其他媒介，如通过海洋再作用于大气和固体地球。 相似文献
7.
顾震年 《中国科学院上海天文台年刊》1996,(17):73-79
本采用国际时间局（BIH）和美国喷气推进实验室（JPL）提供的日长变化序列（LOD）和美国气象中心（NMC）及日本气象厅（JMA）推导出的大气角动量（AAM）来重新检测固体地球和大气之间的季节性差异。从4种滤波序列中发现由AAM推出的LODatm周年变化高于观测的LOD约17％,而LOD的半年振幅变化超出LODatm的约30％。本还讨论了几种因素，例如洋流中季节性变化，气象中的系统误差，平流层风的贡献，核的惯量矩作用，空气质量的重新分布补尝及其他未知的激发源来解释它们之间不平衡，今后10年，在研究角动量不平衡中，将用固体地球－大气－海洋动力学系统来代替简单的固体地球－－大气的两体动力学系统。海洋对这季节性不平衡可能有重要贡献。 相似文献
8.
大气对地球自转参数（ERP）的高频激发 总被引：4，自引：0，他引：4
本文采用１９８３—１９９２年期间由空间大地测量技术观测和归算的地球自转参数（ＥＲＰ）序列，以及由全球气象资料归算的大气角动量（ＡＡＭ）序列，分析和研究了大气对地球自转参数的日长变化（ＬＯＤ）和极移（ｘ和ｙ）在一个月时间尺度以内的高频激发作用，得到的主要结果如下：１大气对ＬＯＤ分量高频潮汐的估计值存在着影响，但是，潮汐形变参数ｋ／ｃ随时间和频率的变化却是受非大气因素的扰动引起的．２．大气可以解释３０天以下ＬＯＤ非潮汐的大部分变化．３．极移分量３０天以内的高频变化也主要由大气激发．ｘ分量与大气的相关性要强于ｙ分量，而且更为稳定，主要表现为平均时间尺度约为２７天的波动，大气对这个波动的贡献可达７０％． 相似文献
9.
大气角动量(AAM) 变化和地球自转变化密切相关,它们可应用于全球环流模型的检验.根据日本气象厅全球环流模型的输出数据计算出AAM 函数,将AAM 函数的模拟值与它的观测值以及地球自转变化序列相比较,来检验该模型对大气角动量的模拟.限于篇幅,仅给出AAM 函数的季节性分量模拟的结果.对于半年项,轴向AAM 函数的气压项和风项的模拟值都偏高,赤道向AAM 函数的气压项和风项很小,因而未予考虑;对于周年项,轴向AAM函数气压项的模拟值偏低,而赤道向AAM 函数气压项的模拟值偏高,轴向AAM 函数的风项模拟得最好,而赤道向AAM 函数的风项模拟得较差.总之,高精度的天文观测的地球自转系列可以作为全球环流模型检验的一种重要参考依据. 相似文献
10.
极移的变化与多种激发息息相关,这些激发包括大气表面压力和大气风、海底压力和洋流、陆地水分布以及气候变暖导致的海平面变化,并且可以通过有效角动量函数来估计.在极移预报中,通过刘维尔方程融合有效角动量函数,并利用最小二乘与自回归组合的方法进行拟合及外推,同时,对自回归模型的可调节参数设置更多的选择,在不同的极移预报阶段,对于不同分量的预报匹配更优的参数,有效地提高了极移的预报精度.在441次1–90 d的极移预报实验中,短中期的预报改善更为明显,在1–6 d和7–30 d的极移X预报结果中,分别有56.9%和53.5%优于国际地球自转服务(International Earth Rotation Service, IERS)的预报;在1–6 d和7–30 d的极移Y预报结果中,分别有66.5%和59.7%优于IERS的预报.整体上,极移Y的预报精度比极移X的预报精度有更多的提升,以IERS的地球定向参数(Earth Orientation Parameters, EOP)产品EOP 14C04 (IAU2000A)为参考,极移X预报在第1 d、第5 d的MAE (Mean Absolute... 相似文献
11.
Many asteroids with a semimajor axis close to that of Mars have been discovered in the last several years. Potentially some of these could be in 1:1 resonance with Mars, much as are the classic Trojan asteroids with Jupiter, and its lesser-known horseshoe companions with Earth. In the 1990s, two Trojan companions of Mars, 5261 Eureka and 1998 VF31, were discovered, librating about the L5 Lagrange point, 60° behind Mars in its orbit. Although several other potential Mars Trojans have been identified, our orbital calculations show only one other known asteroid, 1999 UJ7, to be a Trojan, associated with the L4 Lagrange point, 60° ahead of Mars in its orbit. We further find that asteroid 36017 (1999 ND43) is a horseshoe librator, alternating with periods of Trojan motion. This asteroid makes repeated close approaches to Earth and has a chaotic orbit whose behavior can be confidently predicted for less than 3000 years. We identify two objects, 2001 HW15 and 2000 TG2, within the resonant region capable of undergoing what we designate “circulation transition”, in which objects can pass between circulation outside the orbit of Mars and circulation inside it, or vice versa. The eccentricity of the orbit of Mars appears to play an important role in circulation transition and in horseshoe motion. Based on the orbits and on spectroscopic data, the Trojan asteroids of Mars may be primordial bodies, while some co-orbital bodies may be in a temporary state of motion. 相似文献
12.
Time scales of the transition from contact binary systems of the W UMa type to single stars of the blue straggler type are estimated. A model of one-way mass transfer from the primary component to the companion inside a common envelope (Eggen et al.) and a model of a contact binary lying on the zero-age main sequence with a companion that is losing mass (F. van't Veer) are used to calculate these scales. The merging times of components were calculated for 304 contact systems of the W UMa type from the Catalog of Approximate Photometric and Absolute Elements of Eclipsing Variable Stars on a scale of loss of mass and orbital angular momentum due to magnetic braking, under the assumption of synchronization of the axial rotation and orbital revolution. On the basis of the resulting statistics, the characteristic merging scales are 0.4-0.6 and 0.5-0.7 Gyr, respectively, for the above two models. The results of a comparison with the work of other authors are discussed. 相似文献
13.
Magnetars are the neutron stars with the highest magnetic fields up to 1015–1016 G. It has been proposed that they are also responsible for a variety of extra-galactic phenomena, ranging from giant flares in nearby galaxies to fast radio bursts. Utilizing a relativistic mean field model and a variable magnetic field configuration, we investigate the effects of strong magnetic fields on the equation of state and anisotropy of pressure of magnetars. It is found that the mass and radius of low-mass magnetars are weakly enhanced under the action of the strong magnetic field, and the anisotropy of pressure can be ignored. Unlike other previous investigations, the magnetic field is unable to violate the mass limit of the neutron stars. 相似文献
14.
Pavel Mayer Marek Wolf P. G. Niarchos K. D. Gazeas V. N. Manimanis Drahomír Chochol 《Astrophysics and Space Science》2006,304(1-4):39-41
New precise times of minimum light for several early-type eclipsing binaries were obtained at three observatories. The changes of period of the following measured binaries are discussed: V1182 Aql, LY Aur, SZ Cam, FZ CMa, QZ Car, LZ Cen, V606 Cen, AH Cep and TU~Mus. 相似文献
15.
分析了上两个世纪发生在淮河的洪水事件的可公度性，根据其可公度值及其黄金分割点指出1991年与2003年淮河洪水的不可避免，最后讨论了可公度性的局限及淮河洪水可公度值的可能机制。 相似文献
16.
V.S. Kalantonis E.A. Perdios A.E. Perdiou O. Ragos M.N. Vrahatis 《Astrophysics and Space Science》2003,288(4):479-488
The techniques used for the numerical computation of families of periodic orbits of dynamical systems rely on predictor-corrector
algorithms. These algorithms usually depend on the solution of systems of approximate equations constructed from the periodicity
conditions of these orbits. In this contribution we transform the root finding procedure to an optimization one which is applied
on an objective function based on the exact periodicity conditions. Thus, the determination of periodic solutions and families
of such orbits can be accomplished through unconstrained optimization. In this paper we apply and compare some well-known
minimization methods for the solution of this problem. The obtained results are promising.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
17.
18.
We present a numerical method for inverting long-period components of lightcurves of asynchronous binary asteroids. Data of five near-Earth binary asteroids, (175706) 1996 FG3, (65803) Didymos, (66391) 1999 KW4, (185851) 2000 DP107 and (66063) 1998 RO1, for two of them from more than one apparition, were inverted. Their mutual orbits' poles and Keplerian elements, size ratios, and ellipsoidal shape axial ratios were estimated via this inversion. The pole solutions and size ratios for 1999 KW4 and 2000 DP107 are in a good agreement with independent estimates from radar measurements. We show that uncertainties of estimates of bulk densities of binary systems can be large, especially when observed on short arcs. 相似文献
19.
Influences of the mass, moment of inertia, rotation, absence of stability in the atmosphere and some other parameters of neutron stars on the evolution of pulsars are examined. It is shown that the locations and evolutions of soft gamma repeaters, anomalous X-ray pulsars and other types of pulsar on the period versus period derivative diagram can be explained adopting values of B < 1014 G for these objects if they have smaller mass (e.g. about 0.5 Solar mass) compared to the conventionally adopted values of mass. This approach gives the possibility to explain many properties of different types of pulsar. 相似文献
20.
Results concerning the dependence of photometric and radial velocity amplitudes on metallicity are presented based on about 200 Galactic classical Cepheids pulsating in the fundamental mode. The Galactic distribution of the [Fe/H] value of Cepheids is also studied. We show that the photometric amplitude ratio AI/AV is independent of metallicity. The observed dependence of this ratio on the pulsation period does not correspond to the theoretical predictions. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献