Predictability of the earth's polar motion

The results of a numerical experiment on the predictability of terrestrial polar motion using a Bureau International de l'Heure data set from 1967-83 are presented. A floating point predictor was defined by decomposing polar motion into secular motion and annual and Chandler wobbles. The secular term was linear and the others periodic, the former due to atmospheric mass transport and the latter to Eulerian nutation. A least squares estimator was employed with the data base to obtain constants for the model, which is given the name 'floating-point'. A fixed-period predictor was also devised and, in comparison with the floating point predictor in 6 yr estimates of the annual wobble period, failed after a given length of time. It is suggested that the failure is due to atmospheric motions.