Final answer:
There are four principal lifting mechanisms in the atmosphere: convection, orographic lifting, frontal lifting, and convergence.
Step-by-step explanation:
The number of principal lifting mechanisms that operate in the atmosphere is four. These mechanisms include convection, orographic lifting, frontal lifting, and convergence.
Convection happens when the sun heats the Earth's surface and the air above it, causing the warm air to rise. Orographic lifting occurs when an air mass is forced to rise over a mountain range, cooling as it ascends and potentially forming clouds and precipitation. Frontal lifting is associated with weather fronts where warm air is forced over cooler air. Lastly, convergence refers to the process where two opposing air masses meet and are forced upward, which can also lead to cloud formation and weather events.