EFFECT OF THE PACIFIC-OCEAN ON THE EARTHS SEASONAL WOBBLE INFERRED FROM NATIONAL-CENTER-FOR-ENVIRONMENTAL-PREDICTION OCEAN ANALYSIS DATA

In order to assess oceanic influence on the excitation of the Earth's seasonal wobble, which is not totally explained by atmospheric angular momentum (AAM) we employed Pacific Ocean monthly analysis data from t he U.S. National Center for Environmental Prediction for the period fr om 1980 to 1994 to compute the Pacific Ocean angular momentum (POAM) a round two axes on the equatorial plane. These were chi(1), and chi(2) with respect to axis 1 and axis 2 which corresponded to motion along t he Greenwich meridian and 90 degrees E, respectively. In particular, w e paid attention to the chi(1) component, which was barely influenced by AAM. The variance in the AAM plus FOAM chi(1), was almost 10 times that of the AAM alone, while that of AAM plus FOAM chi(2),decreased to similar to 60% of that of AAM alone. Thus the mean seasonal cycle of FOAM plus AAM roughly accounted for the observed wobble, and its year- to-year fluctuations overlapped with those of seasonal wobble excitati on. We also found that the seasonal chi(1), FOAM mostly.consisted of t he motion (current) term and that the mass term played a secondary rol e; this is in contrast to AAM's contribution to chi(2),. Although inte nsive seasonal fluctuations in the chi(1), motion term were localized around the western Pacific region, we found that middle-to-higher-and lower-latitude regions were inphase and out of phase with the basin-wi de contribution. However, the influence of the Pacific Ocean may be re duced by other unaccounted for sources such as effects from other ocea nic basins and land water.