what are the alternating dark and light bands in jupiter’s atmosphere called
Lightly colored "zones" and relatively dark "belts."
Zones, belts and jets
There are two types of bands: lightly colored "zones" and relatively dark "belts." The wider Equatorial Zone (EZ) extends between latitudes of approximately 7°S to 7°N. 
The dark bands are called "belts", while light ones are called "zones". The dark bands are called "belts", while light ones are called "zones". The dark bands are called "belts", and  the light ones are called "zones"
Atmosphere of Jupiter Atmosphere of Jupiter Atmosphere of Jupiter
Introduction Introduction Introduction
The bands alternate in color: the dark bands are called "belts", while light ones are called "zones".  The upper ammonia clouds visible at Jupiter's surface are organized in a dozen zonal bands parallel to the equator and are bounded by powerful zonal atmospheric flows (winds) known as "jets". The bands alternate in color: the dark bands are called "belts", while light ones are called "zones".   The bands alternate in color: the dark bands are called "belts", while light ones are called "zones"
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Atmosphere of Jupiter [SEP] Zones, belts and jets
The visible surface of Jupiter is divided into several bands parallel to the equator. There are two types of bands: lightly colored "zones" and relatively dark "belts." The wider Equatorial Zone (EZ) extends between latitudes of approximately 7°S to 7°N. Above and below the EZ, the North and South Equatorial belts (NEB and SEB) extend to 18°N and 18°S, respectively. Farther from the equator lie the North and South Tropical zones (NtrZ and STrZ). The alternating pattern of belts and zones continues until the polar regions at approximately 50 degrees latitude, where their visible appearance becomes somewhat muted. The basic belt-zone structure probably extends well towards the poles, reaching at least to 80° North or South.