INTERANNUAL VARIATION OF EARTH ROTATION,El Nio EVENTS AND ATMOSPHERIC ANGULAR MOMENTUM

In this paper the multi-stage digit filter is used to analyse the data of Earth rotation represented by the length of day, ΔLOD. The results show that the interannual variations of Earth rotation, which are in the time scale of several years but not quasi-periodic terms, exist in the long periodic fluctuations. They induce the relative variation in the length of day of 0.3×10~(-8).Comparing the series of length of day with the data of temperature departure of the sea surface in the equatorial area of the eastern Pacific, we found that the deceleration and acceleration of the interannual rate of Earth rotation are consistent with the warming up and down of sea temperature in the equatorial area very well. This means that every El Nio event always occurs after the turning of acceleration of the interannual rate of Earth rotation to deceleration.According to the strong interannual variation in the length of day and strong warming of the sea surface temperature in the equatorial area between 1982 and 1983     

地球自转年际变化、El Ni■o事件和大气角动量

本文采用多级数字滤波技术,分析了25年(1962—1986年)的地球自转日长变化△LOD资料,结果表明在地球自转的长期起伏过程中,伴随着时间尺度为几年的非准周期性的年际波动,它使日长产生0.3×10~(-8)量级的相对变化。通过年际日长变化时间序列与表征El Nio事件的东太平洋赤道带海温资料比较,发现地球自转年际速率的减慢和加快,与赤道海温的增暖和减暖现象存在着很好的一致性。根据较强的日长年际变化和赤道海温最大增暖现象,文中还分析了用全球带风资料所归算的大气角动量(AAM),发现其年际变化超前2—3个月。由此认为,地球自转的年际变化和El Nio事件,可能是固体地球和海洋各自对大气环流变异的响应。上述分析表明,利用天文常规观测所测定的UT_1资料,归算和监视△LOD序列的极小值,可以对El Nio事件作出预测期约为1年的长期预报。