摘要
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．
The data sets of the △LOD measured by space geodetic techniques and the atmospheric angular momentum (AAM) reduced with the global meteorological data from 1979 through 1995 by NMC and NCEP/NCAR are used in mis work to reanalyze and study the excitation of the length of day (LOD), and to examine and compare the contribution of each AAM to △LOD The main results are as follows:(1)The AAM feanalyzed with assimilated global meteorological data by NCEP/NCAR are more accurate and have lower noises than the original AAM reduced by NMC.The NCEP/ NCAR AAM is better consistent to the CLOD. (2) The AAM reanalyzed with assimilated global meteorological data may better interpret the non-tidal variation of LOD from intraseasonal to interannual time scale, especially on the quasi-biennial time scale. But the atmosphere still cannot explain all LOD variations, so maybe there are other excitahon scarces. (3) The effects of the atmosphere on the estimated values of tides for △LOD components are weak. The preliminary estimated results of the annual and semiannual tides can be obtained after removing the effects of the atmosphere from △LOD.
出处
《天文学报》
CSCD
北大核心
1998年第2期122-130,共9页
Acta Astronomica Sinica
基金
国家自然科学基金
国家八五重大关键性基础研究资助
关键词
日长变化
大气角动量
length-of-day variahon, atmospheric angular momentum
