What describes the process of convection in the atmosphere?

Convection in the atmosphere is primarily described by the process where warm air rises and cool air sinks. This movement occurs due to differences in temperature and density. When air is heated, it becomes less dense and rises; as it cools down, it becomes denser and sinks. This cycle creates a convection current, which is a crucial mechanism for heat transfer in the atmosphere. These rising and sinking motions are fundamental to many weather phenomena, including cloud formation and storm development.

The other options pertain to different atmospheric processes. The exchange of moisture between ocean and land refers to evaporation and precipitation processes rather than convection directly. The formation of frontal systems involves the interaction between air masses but is not itself representative of convection. The buildup of static electricity in clouds relates to processes like charge separation and lightning rather than the convection process. Thus, option A correctly encapsulates the essence of convection in the atmosphere.