  ESA's Jupiter Icy Moons Explorer (JUICE) will provide a detailed
investigation of the Jovian system in the 2030s, combining a suite of
state-of-the-art instruments with an orbital tour tailored to maximise
observing opportunities. We review the Jupiter science enabled by the JUICE
mission, building on the legacy of discoveries from the Galileo, Cassini, and
Juno missions, alongside ground- and space-based observatories. We focus on
remote sensing of the climate, meteorology, and chemistry of the atmosphere and
auroras from the cloud-forming weather layer, through the upper troposphere,
into the stratosphere and ionosphere. The Jupiter orbital tour provides a
wealth of opportunities for atmospheric and auroral science: global
perspectives with its near-equatorial and inclined phases, sampling all phase
angles from dayside to nightside, and investigating phenomena evolving on
timescales from minutes to months. The remote sensing payload spans far-UV
spectroscopy (50-210 nm), visible imaging (340-1080 nm), visible/near-infrared
spectroscopy (0.49-5.56 $\mu$m), and sub-millimetre sounding (near 530-625\,GHz
and 1067-1275\,GHz). This is coupled to radio, stellar, and solar occultation
opportunities to explore the atmosphere at high vertical resolution; and radio
and plasma wave measurements of electric discharges in the Jovian atmosphere
and auroras. Cross-disciplinary scientific investigations enable JUICE to
explore coupling processes in giant planet atmospheres, to show how the
atmosphere is connected to (i) the deep circulation and composition of the
hydrogen-dominated interior; and (ii) to the currents and charged particle
environments of the external magnetosphere. JUICE will provide a comprehensive
characterisation of the atmosphere and auroras of this archetypal giant planet.
