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

Abstract

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, we analysed the data from atmospheric angular momentum (AAM) calculated by using the global zonal wind data, and found that the interannual variation in AAM has an excess of two to three months. We suggest that the interannual variations in Earth rotation and the El Nio events are probably responses of solid earth and ocean, respectively, to the anomaly of atmospheric circulation.It is also shown in oar analysis that the minimum of ΔLOD series, which is deduced from UT1 data observed regularly with astrometry, can predict the occurrence of the El Nio events for a long range forecast about one year.