Oscillating motion of the jovian great red spot and numerical experiments with IG equation

Position measurements of the Great Red Spot (GRS) on recent digital images of Jupiter were carried out to detect the longitudinal and latitudinal motion of the GRS. Its longitudinal oscillating motion may be interpreted as two types. One has a 57-day period and no latitudinal motion, the other has 86 days and probably has latitudinal motion. In 86 days, oscillation, the GRS seems to locate equatorward when it moves relatively westward, and poleward when it moves eastward. Numerical Experiments of the Intermediate Geostrophic (IG) equation show the same results for the motion of an eddy, and that a kind of wave collides with the eddy when it changes relative longitudinal motion from eastward to westward.