zone

The term zone is used for light-colored, horizontal (east-west) bands (defined concentric patterns) on planets such as Jupiter and Saturn, and similar phenomena on other planets. The intervening dark-colored bands are termed belts. Such bands are a manifestation of a zonal flow, the results of cell wind patterns such as Hadley cells. The differences in color are due to differences in the constituents of the atmosphere that the cells bring to the visible surface. Between the cells, i.e., between the zones and belts, are jets, i.e., jet streams. The flows may well be unlike Earth's in planets with such deep atmospheres.

The term zone has numerous other uses in astrophysics, e.g., habitable zone, zone of avoidance, convection zone, radiation zone, partial ionization zone, and dead zone.