  Rotational modulations are observed on brown dwarfs and directly imaged
exoplanets, but the underlying mechanism is not well understood. Here, we
analyze Jupiter's rotational light curves at 12 wavelengths from the
ultraviolet (UV) to the mid-infrared (mid-IR). Peak-to-peak amplitudes of
Jupiter's light curves range from sub percent to 4% at most wavelengths, but
the amplitude exceeds 20% at 5 $\rm \mu m$, a wavelength sensing Jupiter's deep
troposphere. Jupiter's rotational modulations are primarily caused by discrete
patterns in the cloudless belts instead of the cloudy zones. The light-curve
amplitude is dominated by the sizes and brightness contrasts of the Great Red
Spot (GRS), expansions of the North Equatorial Belt (NEB), patchy clouds in the
North Temperate Belt (NTB) and a train of hot spots in the NEB. In reflection,
the contrast is controlled by upper tropospheric and stratospheric hazes,
clouds, and chromophores in the clouds. In thermal emission, the small
rotational variability is caused by the spatial distribution of temperature and
opacities of gas and aerosols; the large variation is caused by the $\rm
NH_{3}$ cloud holes and thin-thick clouds. The methane-band light curves
exhibit opposite-shape behavior compared with the UV and visible wavelengths,
caused by wavelength-dependent brightness change of the GRS. Light-curve
evolution is induced by periodic events in the belts and longitudinal drifting
of the GRS and patchy clouds in the NTB. This study suggests several
interesting mechanisms related to distributions of temperature, gas, hazes, and
clouds for understanding the observed rotational modulations on brown dwarfs
and exoplanets.
