Final answer:
The circulation of air in a Hadley cell is driven by multiple factors, including the heating of tropical air by the sun, the sinking of cold polar air, the dry desert conditions around 30 degrees N and 30 degrees S, and the fluctuation of air patterns between latitudes of 30 degrees and 60 degrees.
Step-by-step explanation:
The circulation of air in a Hadley cell is driven by multiple factors. One of the main drivers is the heating of tropical air by the sun. As the sun heats the air near the equator, it rises and creates a low-pressure area. This causes air to flow from the tropics towards the poles. Additionally, the sinking of cold polar air contributes to the circulation as it moves towards the equator. The dry desert conditions around 30 degrees N and 30 degrees S also play a role, creating a belt of high pressure and causing air to sink and flow back towards the equator. Lastly, the fluctuation of air patterns between latitudes of 30 degrees and 60 degrees further affects the circulation of air in a Hadley cell.