Hubble space telescope observations of the 1990 equatorial disturbance on Saturn: Zonal winds and central Meridian albedos

Two sets of Hubble Space Telescope (HST) data, obtained in August 1990 and November 1990, are compared with Voyager 1 and 2 data acquired in 1980 and 1981. A rare disturbance developed in the equatorial region of Saturn in late September 1990. Due to the large equatorial wind shear, this disturbance generated inhomogeneous bright cloud structures in the equatorial region that extended to 25° north latitude in November 1990. Meridional albedo scans and wind measurements from the Voyager northern spring equinox and the HST northern summer observations are compared. Differences in average zonal winds in the images obtained with the green F547M and the methane F889N filters are interpreted as evidence of vertical shear in the zonal winds. Longitudinal variations in the equatorial zonal winds are interpreted as evidence of interaction between the storm nucleus, generated during the disturbance, and the local wind field.