Task: Class Definition Understanding (ontology: Earth_Environment/SWEET)

Which of the following definitions best describes 'convection cell'?

A. A regular pattern of convective cells that can develop in an atmospheric boundary layer heated from below or radiatively cooled from cloud top. This phenomenon is readily observed in satellite imagery during cold air outbreaks when continental air passes over the relatively warm coastal ocean. Cloud lines, marking horizontal roll vortices, form initially in the developing marine atmospheric boundary layer. These lines evolve into open cells, which are defined by clouds in the upward motion along the edges of honeycomb- shaped cells, with less cloudy subsiding air in their centers. The convective structure further evolves into closed cells, which have cloudy centers and cloud-free edges.
B. The vorticity as measured in a system of coordinates fixed on the earth's surface. Usually, only the vertical component of the vorticity is meant.
C. A bow-shaped line of convective cells that is often associated with swaths of damaging straight-line winds and small tornadoes.
D. An organized unit of convection within a convecting layer. It is isolated by a stream surface, with ascending motion in the center and descending motion near the periphery, or vice versa.

Answer: An organized unit of convection within a convecting layer. It is isolated by a stream surface, with ascending motion in the center and descending motion near the periphery, or vice versa.