Seasonal oscillations in length-of-day

Variations of annual and semiannual oscillations in rotation parameters have been investigated on the basis of length-f-ay(LOD) as well as atmospheric-ngular-omemtum (AAM) series. These oscillations were determined using band-ass filters. In order to show the character of variations of seaasonal oscillations, amplitudes, phases and periods were computed by a least-quares adjustment with the method of modified harmonic analysis at quarterly intervals. In addition, the seasonal imbalances in LOD and AAM budgets were determined and analysed in a similar way. These discrepancies were corrected for tidally excited effects. The non-tmospheric oscillations without the annual tide effect Sa and the semiannual tide effect Ssa have variable amplitudes between 0.02 and 0.10 msec.     

大气角动量变化以及对地球自转季节变化的激发

利用日本气象局AMIPⅡ大气数值模式的输出结果，基于BP方法和SP方法计算了1979年至1996年大气角动量变化以及对地球自转季节变化激发的差异。利用最小二乘谐波拟合方法和气候平均图方法，分析了大气角动量的季节变化，并与同时期采用NCEP再分析资料和JMA客观分析资料计算的大气角动量进行比较。     

50-day Oscillation of Length-of-day Change

Variations of Earth’s rotation rate (length-of-day, LOD) occur over a wide range of time scales from a few hours to the geological age. Studies showed that the 50-day fluctuation exists in LOD change. In the present paper, the authors use wavelet technique to study the 50-day oscillation in LOD series. Temporal variations of the oscillation are presented in this work. After analyzing the axial component of atmospheric angular momentum (AAM) and oceanic angular momentum (OAM), the 50-day periodic signal is also found in atmospheric and oceanic motion with remarkable time-variation. Meanwhile, the 50-day oscillation of the axial AAM is in good consistence with that of LOD change. This suggests that the 50-day oscillation of LOD change is mainly excited by the axial AAM. Possible origin of the oscillation for Earth system is discussed in the end of this paper.     

Atmospheric and Oceanic Excitations to LOD Change on Quasi-biennial Tune Scales

We use wavelet transform to study the time series of the Earth's rotation rate (length-of-day, LOD), the axial components of atmospheric angular momentum (AAM) and oceanic angular momentum (OAM) in the period 1962-2005, and discuss the quasi-biennial oscillations (QBO) of LOD change. The results show that the QBO of LOD change varies remarkably in amplitude and phase. It was weak before 1978, then became much stronger and reached maximum values during the strong El Nino events in around 1983 and 1997. Results from analyzing the axial AAM indicate that the QBO signals in axial AAM are extremely consistent with the QBOs of LOD change. During 1963-2003, the QBO variance in the axial AAM can explain about 99.0% of that of the LOD, in other words, all QBO signals of LOD change are almost excited by the axial AAM, while the weak QBO signals of the axial OAM are quite different from those of the LOD and the axial AAM in both time-dependent characteristics and magnitudes. The combined effects of the axial AAM and OAM can explain about 99.1% of the variance of QBO in LOD change during this period.     

JMAGCM模拟的大气角动量函数Ⅰ.季节性分量(英文)

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.     

A possible contribution of the solar wind to annual fluctuation in the Length of Day

Applying Vondrák narrow-band filters on high precision Length of Day (LOD) measurements provided by space observation techniques as well as Atmosphere Angular Momentum (AAM) computed by U.S. National Meteorological Center (NMC), we show variation in amplitude of the annual components. From filter series of LOD and AAM, we find that annual variation of the LOD induced by AAM is about 20% higher than observed one. The aim of this work is to investigate how far the torque applied by the solar wind on the Earth's magnetosphere could contribute to explain this excess. The advocated dynamical mechanism could counterbalance annual discrepancies between AAM and LOD by an amount of 20%. Therefore, the torque produced by the solar wind on the earth might be considered as one of the most possible contributions to annual fluctuation in LOD.     

大气对地球自转季节性变化的贡献

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。     

同ENSO现象相关联的日长亚季节变化

本文利用小波分析方法研究了地球自转日长亚季节近50天和近120天周期变化的时频特征．结果表明,日长近120天周期变化及近50天周期变化的振幅具有明显的年际变化．ENSO事件发生之前,日长近50天周期变化加强,进入ENSO时期,逐渐减弱,成为ENSO产生的先兆之一,同时,日长近120天周期变化显著增强80年代,日长近50天周期变化明显发生了两次周期分岔分岔的一种趋势经历了一个周期延长的过程,收敛于ENSO时期增强的近120天周期变化,该过程不仅与ENSO现象相关联而且可能受到近10年波动的调制作用.同时证实了日长近120天周期变化及近50天周期变化的激发机制主要是同频段的大气环流变化所导致。     

Periodicities in Global Mean TEC from GNSS Observations

As an important measurement parameter, global total electron content (TEC) is appropriate for the study of the Sun–Earth connection. In this paper, the wavelet technique is employed to investigate the periodicities in global mean TEC during 1995–2008. Analysis results show several remarkable components (including 27-day, semiannual and annual cycles) existing in global mean TEC with obvious time-variable characteristics, besides 11-year cycle. After analyzing sunspot numbers and solar extreme ultra-violet (EUV) radiation variations during this time period, except for semiannual variations, close correlation between global mean TEC and solar variations is found, especially, a strong resemblance of the 27-day fluctuation exists in global mean TEC, sunspot and solar EUV radiation variations.     

Satellite observed long-term averaged seasonal and spatial ozone variations in the stratosphere

Nine years of Nimbus-7 SBUV ozone mixing ratio data (October 1978–September 1987) have been used to analyze the distributions of the long-term average annual and semiannual ozone oscillations in the lower, middle, and upper stratosphere over the region 65°S to 65°N. It is shown that the derived harmonics are consistent with the results of earlier investigations based on limited sets of data. Year-to-year changes of amplitudes of the annual and semiannual variations are generally small except in the tropical midstratosphere (due to the effect of El Chichon) and the southern subpolar upper stratosphere.

Analyses are also presented to show the vertical and seasonal distribution of the zonal ozone variations. It is shown that, for the long-term averaged data, wave 1 is larger during winter than summer and in winter larger in the Northern than Southern Hemisphere. The importance of photochemical and thermal/dynamic processes in modifying the time and zonal variations is discussed.     

地球自转极移近120天准周期变化的小波分析及其大气激发机制

本文利用小波变换这一新的频谱分析方法研究了地球自转极移近１２０天准周期变化的时频特征，证实了在极移序列中存在显著的近１２０天准周期振荡，得到了极移准周期变化的周期与振幅随时间变化的规律．以地球自转动力学为基础，在时域内分析了大气变化对自转极移季节内变化的激发．表明大气激发在本文所研究的频段内是极移短周期变化的主要激发源。并发现在极移近１２０天准周期振荡平静时期，发生ＥＬＮｉｎｏ事件，同时日长变化近１２０天准周期变化增强．     

地球自转日长变化(LOD)和大气角动量(AAM)所对应的动力系统

利用一个多分维的分形地应的一维映射可以用子波变换反演出来,对地自转日长（ＬＯＤ）资料和大气角动量（ＡＡＭ）资料进行子波变换说明,在２０年尺度上、周年尺度和２－３２年尺度上,ＬＯＤ和ＡＡＭ的突变时间基本一致,所反演出的不同层次上分岔时间的分段映射动力系统也极其相似。     

A semiannual geomagnetic variation that is not dependent on the heliographic latitude effect

Hourly means of the geomagnetic elements recorded at Lerwick have been analysed to determine the effect of monthly sunspot number on the solar and lunar daily variations. The diurnal term of the solar variation in declination is found to have a distinct semiannual component that is independent of sunspot number. Thus this semiannual variation is not generated by the heliographic latitude or axial process proposed by Cortie (1912).     

大气对地球自转参数（ERP）的高频激发

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％．     

Evidence for the phi-dependent rotation-oscillation of the Sun (and for the driving mechanism of the asymmetric dynamo)

Longitude-dependent oscillations of the solar rotation are derived from the 27-day averages of the photospheric velocity data. Two pairs of prominent periods are obtained. Their harmonic means correspond to a semiannual variation and to the first harmonic of the latter. To explain the origin of the oscillation the corona and the interplanetary material are supposed to rotate parallel to the planetary plane with an inclination to the solar equator. The non-uniform shearing around the equator is assumed to result in oscillation with a period of half of a year.     

利用Lageos 1 SLR资料解算1990-2001年的地球定向参数

利用 12年的Lageos 1卫星激光测距资料 (1990 - 2 0 0 1)解算得到了地球定向参数 (EOP) ,将该序列的结果与同期的EOP(IERS)C0 4进行比较 ,其外符精度为 :极移XP— 0 .4 0mas,YP— 0 .4 2mas ,日长变化Dr— 0 .0 35ms。     

Diurnal variations of cosmic rays during a solar magnetic cycle

We have used data from five neutron monitor stations with primary rigidity (Rm) ranging from 16 GeV to 33 GeV to study the diurnal variations of cosmic rays over the period: 1965–1986 covering one 22-year solar magnetic cycle. The heliosphere interplanetary magnetic field (IMF) and plasma hourly measurements taken near Earth orbit, by a variety of spacecraft, are also used to compare with the results of solar diurnal variation. The local time of maximum of solar diurnal diurnal variations displays a 22-year cycle due to the solar polar magnetic field polarities. In general, the annual mean of solar diurnal amplitudes, magnitude of IMF and plasma parameters are found to show separte solar cycle variations. Moreover, during the declining period of the twenty and twenty-ne solar cycles, large solar diurnal amplitudes are observed which associated with high values of solar wind speed, plasma temperature and interplanetary magnetic field magnitude B3.     

The semiannual variation in the magnetic activity indices Aa and Ap

The technique of Complex Demodulation is used to examine the long-term modulation of the semiannual variation in planetary magnetic activity as characterised by the A_a index for 1868–1980 and the A_p index for 1932–1980. From the phase results, strong support is found for an “equinoctial” mechanism for the semiannual variation. The amplitude shows a quasi 11 -year modulation for most of the period of analysis and a pronounced increase over the years 1938–1966 approximately. Comparison of the long-term modulation of the semiannual variation in activity, with that of the occurrence of stormy days suggests that the semiannual modulation is energy dependent, being more effective with increasing energy.     

Tensor anisotropy of cosmic rays

Long-termobservations of the muon intensity of galactic cosmic rays at the Nagoya (35°10′ N, 136°58′ E) and Yakutsk (62°01′ N, 129°43′ E) stations have revealed amplitude-phase annual and semiannual oscillations of the semidiurnal variation. These oscillations are attributable to the properties of the cosmic-ray anisotropy tensor that result from shielding by the interplanetary magnetic field and solar-wind shear flow. The mentioned tensor is also shown to have a north-south asymmetry.     

Cycling Changes in the Amplitudes of the 27-Day Variation of the Galactic Cosmic Ray Intensity

We study quasi-periodical changes in the amplitudes of the 27-day variation of the galactic cosmic ray (GCR) intensity, and the parameters of solar wind and solar activity. We have recently found quasi-periodicity of three to four Carrington rotation periods (3?–?4 CRP) in the amplitudes of the 27-day variation of the GCR intensity (Gil and Alania in J. Atmos. Solar-Terr. Phys. 73, 294, 2011). A similar recurrence is recognized in parameters of solar activity (sunspot number, solar radio flux) and solar wind (components of the interplanetary magnetic field, solar wind velocity). We believe that the 3?–?4 CRP periodicity, among other periodicities, observed in the amplitudes of the 27-day variation of the GCR intensity is caused by a specific cycling structure of the Sun’s magnetic field, which may originate from the turbulent nature of the solar dynamo.