  Jupiter's banded structure undergoes strong temporal variations, changing the
visible and infrared appearance of the belts and zones in a complex and
turbulent way due to physical processes that are not yet understood. In this
study we use ground-based 5-$\mu$m infrared data captured between 1984 and 2018
by 8 different instruments mounted on the Infrared Telescope Facility in
Hawai'i and on the Very Large Telescope in Chile to analyze and characterize
the long-term variability of Jupiter's cloud-forming region at the 1-4 bar
pressure level. The data show a large temporal variability mainly at the
equatorial and tropical latitudes, with a smaller temporal variability at
mid-latitudes. We also compare the 5-$\mu$m-bright and -dark regions with the
locations of the visible zones and belts and we find that these regions are not
always co-located, specially in the southern hemisphere. We also present
Lomb-Scargle and Wavelet Transform analyzes in order to look for possible
periodicities of the brightness changes that could help us understand their
origin and predict future events. We see that some of these variations occur
periodically in time intervals of 4-8 years. The reasons of these time
intervals are not understood and we explore potential connections to both
convective processes in the deeper weather layer and dynamical processes in the
upper troposphere and stratosphere. Finally we perform a Principal Component
analysis to reveal a clear anticorrelation on the 5-$\mu$m brightness changes
between the North Equatorial Belt and the South Equatorial Belt, suggesting a
possible connection between the changes in these belts.
