Global changes of zonal cloud structure on Jupiter have been observed and analyzed from data obtained with a 1-m telescope and a low-dispersion spectrograph in the spectral range λλ400--680 nm, and with a 70-cm telescope and planetary three-channel spectrometer in the spectral range λλ320--1100 nm during each Jovian apparition from 1988 to 1992. Variations of the observed meridional intensity profiles and relative spectrophotometric gradients are described as well as the changes of absolute spectral reflectivity of five main belts on Jupiter (North and South Equatorial belts, North and South Tropical zones, and Equatorial region). Some peculiarities in the behavior of spectrophotometric gradients may be interpreted as a result of increased Rayleigh scattering in the gas layer over the deeper effective cloud boundary within main dark belts. The polar limb darkening varies only slightly with wavelength and it may be considered as evidence for dark aerosols in the stratosphere at high latitudes. The intensity of the methane absorption band centered at 8860 ¿ shows an increase from the equator to temperate latitudes throughout the 1988--1992 period, despite the large variations in belt and zone reflectivities observed during this period in the southern hemisphere. ¿ American Geophysical Union 1994