海洋和大气对Chandler摆动激发的贡献

CONTRIBUTION OF OCEANIC AND ATMOSPHERIC EXCITATIONS TO THE CHANDLER WOBBLE

用 198 5～ 1995年期间海洋角动量变化序列和大气角动量变化序列 ,分析它们对Chandler摆动的激发能量以及它们与天文观测激发的相干性 .结果表明 ,在Chandler摆动频带内 ,海洋角动量变化提供的激发能量大约占观测激发的 6 4 % ,其中洋底压力变化起主导作用 ;NCEP NCAR(美国国家环境预测中心 国家大气研究中心 )和JMA(日本气象厅 )大气角动量变化提供的激发能量分别为观测激发的 2 3%和 2 14 % .海洋激发与观测激发的相干系数约为 0 .5 2 ,接近 99%置信度下限 (0 .5 4 ) ,海洋激发的相位滞后观测激发约 19° ;NCEP NCAR和JMA的大气激发与观测激发的相干系数分别为 0 .32和 0 .37,大气激发的相位超前观测激发分别约 4 7°和 19°.用更短期间 (9年、6年 )的海洋和大气角动量序列与更长期间 (16、39年 )的大气角动量序列作分析表明 ,在Chandler摆动频带内 ,无论是它们的激发能量 ,还是它们与观测激发之间的相干系数都呈现很大的变化 ,而且这些变化具有某种程度的随机性 .

By using the data sets of the oceanic and atmospheric angular momentum during 1985～1995, the mean energy of the oceanic and atmospheric excitation in Chandler wobble band (CWB) is estimated and compared with that of the geodetically observed excitation. Results show that the variation of the oceanic angular momentum (OAM) can provide about 64% of the excitation energy in CWB with a dominant contribution of the oceanic bottom pressure, while the excitation energy provided by the atmospheric angular momenta (AAM(NCEP/NCAR) and AAM(JMA)) is about 23% and 214% in comparison with the observed one. Squared coherence, 0.52 (0.32 and 0.37), is also estimated between the observed excitation and the OAM (AAM(NCEP/NCAR) and AAM(JMA)) excitations. Coherent phases show a lagging phase about 19° for OAM excitation, leading phases about 47° for AAM(NCEP/NCAR) and 19° for AAM(JMA), relative to the observed excitation,respectively. Analyses of some shorter (9 and 6 yrs.) and longer (16 and 39 yrs.) data series indicate that either the excitation energy, or the squared coherence are temporally variable, and their variability are of, in some extent, stochastic property.