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％．     

地球自转、大气角动量和太阳活动的30—60天波动特征

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。     

大气角动量资料源的变化对研究日长变化激发的贡献

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．     

极移的半年振荡和大气激发的贡献

本文采用国际地球自转服务（IERS）测定的均匀极坐标序列及日本气象局（JMA）提供的大气激发函数赤道分量而求得的激发极移序列来研究它们的半年振荡变化。两种序列进行了比较，相关估计给出x相对于m1的相关系数为0.69，y相对于m2的相关系数为0.52。因此，我们认为大气质量角动量赤道分量对极移半年项有一部分贡献。这些影响表现在x轴方向稍强于y轴方向。结果表明：观测极移和激发极移的半年振荡的周期及振幅都是随时间而变化的。     

全球地表水储量再分布对周年极移的激发

利用全球降水和蒸发观测同化资料以及国际大气模式比较计划和国际大气海洋耦合模式比较计划中的陆面过程数值模式，计算比较了地表水储量角动量变化对周年极移的激发，分析结果表明基于3种资料的地表水储量角动量变化对极移周年正向频率的激发约占大气周年正向激发的10%至25%，研究结果尽管显示大气，海洋和地表水的综合周年正向激发与极移测地周年正向激发十分相近，鉴于海洋角动量数值分析的差异和目前对全球水循环观测的水准以及对水循环平衡问题有限的理解，仍然期待更为客观的全球海洋，陆面动力过程和数值分析方法用于完善全球地表水储量变化对周年极移激发的研究。     

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．     

大气对极移的非季节性激发贡献

本文对由高精度的极移资（Ｓｐａｃｅ９３序列）所推导出的测地激发函数和由日本气象局（ＪＭＡ）提供的大气激发函数中的非季节性波动进行了研究，在两个序列中都显示出较强的４０－６０天的波动．在非季节性的时间尺度上，测地激发函数相关于大气压力变化，与与的相关系数分别为０．４４和０．５８，这表明了大气角动量对极移中ｙ轴方向的非季节性变化的影响稍大于ｘ轴方向．而且，大气和测地激发函数尤其在Ｘ２方面具有较相似的时间变化谱．这些事实说明：极移的非季节振荡至少部分地由气压变化所引起，它在１４０天以下周期的极移激发中起了一定的作用．     

全球陆地水储量对地球自转变化的激发作用

用美国环境预测中心和美国大气研究中心(NCEP/NCAR)40年重新分析计划气候数据同化系统(CDAS)所得到的全球陆地水储量(土壤湿度和积雪水当量)数据,对地球自转变化(极移和日长)的激发作用作了分析．结果表明,陆地水储量对周年地极移动正频分量的激发为17．8mas,与大气激发相当,相位滞后约48°．其中,积雪水当量的激发结果与用人卫遥感技术所得到的积雪水当量激发的正、负频率分量的振幅和相位都符合得很好． 用陆地水储量数据得到对日长变化周年分量的激发作用约49μs,约占观测激发的15％,相位滞后约23°;对日长变化半年分量的激发作用约9μs,约占观测激发的3％,相位滞后约122°．     

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

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．     

全球海洋对极移周年运动的激发

目前海洋对极移季节变化的激发尚未得到合理的定量结果.许多研究已经表明大气运动是极移季节变化最大的激发源,海洋运动是剩余部分最主要的激发源之一.利用新一代SODA海洋同化资料(SODA_1.4.2和SODA_1.4.3)以及ECCO海洋同化资料,深入研究了1992—2004年全球海洋对极移周年变化的激发以及激发随纬度的分布.结果表明,SODA海洋激发的季节变化与从测地激发函数中扣除大气、陆地水作用剩余部分的季节变化在所研究的大部分时段非常接近,二者的周年振幅和位相结果基本相当.此外,与早期SODA_Beta 7的结果比较,新一代的SODA海洋激发有了明显改善.SODA和ECCO海洋对极移周年激发的纬度分布,在格林威治方向上比较一致;在东经90°方向上有明显的差别.     

Contribution of the atmosphere to the seasonal changes in earth's rotation

Using new data of atmospheric angular momentum for the period 1975–1995, the contributions of the atmosphere to the changes in LCD and polar motion on the seasonal time scale are investigated. The results show that, when the effects of wind and atmospheric pressure are considered, the atmosphere's contribution on the annual and semi-annual time scales may reach, respectively, 95% and 88%. We also give some quantitative results of the atmosphere's excitation of polar motion. On the annual time scale, the contribution to the X-component of polar motion is 16% and that to the Y-component is 43%. On the semi-annual time scale, the contributions to the X- and Y-components are, respectively, 9% and 30%. From the above results, it is clear that the contribution of the ocean should also be included in a more complete solution of the problem of excitation of the earth's rotation.     

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。     

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.     

Atmospheric angular momentum variations of Earth, Mars and Venus at seasonal time scales

Atmospheric angular momentum variations of a planet are associated with the global atmospheric mass redistribution and the wind variability. The exchange of angular momentum between the fluid layers and the solid planet is the main cause for the variations of the planetary rotation at seasonal time scales. In the present study, we investigate the angular momentum variations of the Earth, Mars and Venus, using geodetic observations, output of state-of-the-art global circulation models as well as assimilated data. We discuss the similarities and differences in angular momentum variations, planetary rotation and angular momentum exchange for the three terrestrial planets. We show that the atmospheric angular momentum variations for Mars and Earth are mainly annual and semi-annual whereas they are expected to be “diurnal” on Venus. The wind terms have the largest contributions to the LOD changes of the Earth and Venus whereas the matter term is dominant on Mars due to the CO₂ sublimation/condensation. The corresponding LOD variations (ΔLOD) have similar amplitudes on Mars and Earth but are much larger on Venus, though more difficult to observe.     

基于有效角动量函数的多参数极移预报

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...     

Atmospheric Excitation of Time Variable Length-of-Day on Seasonal Scales

We use the method of wavelet transform to analyze the time series of the Earth's rotation rate of the EOP(IERS)C04.The result shows that the seasonal (annual and semiannual)variation of the length-of-day(LOD)has temporal vari- ability in its period length and amplitude.During 1965.0-2001.0,the periods of the semiannual and annual components varied mainly from 175-day to 190-day and from 360-day to 370-day,respectively;while their amplitudes varied by more than 0.2 ms and 0.1 ms,respectively.Analyzing the axial component of atmospheric angular mo- mentum(AAM)during this period,we have found that time-variations of period lengths and amplitudes also exist in the seasonal oscillations of the axial AAM and are in good consistency with those of the seasonal LOD change.The time variation of the axial AAM can explain largely the change of the LOD on seasonal scales.     

On the interpretation of seasonal variations of stratospheric ozone

Insight into the causes of the annual and semi-annual ozone oscillations may be gained from the analysis of photochemical model behavior. In this paper, the monthly variations of the ozone mixing ratio computed by the two-dimensional photochemical model of Garcia and Solomon (1983, J. geophys. Res. 88, 1379) are Fourier-analyzed and compared with SBUV observations of ozone mixing ratio. Remarkably good qualitative agreement between the model calculations and the observations is found. Analysis of computed transport and chemical production and destruction rates reveals the causes of the modelled seasonal ozone variations.

It will be shown that at high latitudes and low altitudes, modelled ozone abundances increase in the winter due to transport and decrease in the summer due to chemical destruction. In the middle stratosphere, the calculated annual ozone variation is largely due to the annual variation in the odd-oxygen production rate, and in the upper stratosphere, the computed annual ozone variation is caused by the large calculated annual oscillation in temperature. Comparison between the model and observations suggests that the equatorial semi-annual oscillation above 10 mb is caused mainly by the semi-annual temperature and wind oscillation (SAO). Below 10 mb the computed equatorial ozone variation is caused by the increased rates of odd-oxygen production associated with the semi-annual zenith crossings of the Sun. Finally, the calculated polar semi-annual ozone oscillations are found to be caused by modulation of the radiatively driven middle-stratospheric ozone variation by temperature dependent chemical destruction processes.