Rainfall is primarily determined by what factor?

Rainfall is primarily determined by global circulation patterns, which are large-scale wind patterns that distribute heat and moisture around the Earth. These patterns are driven by the uneven heating of the Earth’s surface by the sun, which leads to the formation of different pressure zones.

In the tropics, warm air rises, cools, and condenses to form clouds, leading to precipitation. As this air moves towards the poles, it cools further and contributes to different weather patterns. Areas around the equator experience high rainfall due to the convergence of trade winds and the presence of the Intertropical Convergence Zone (ITCZ), where warm air rises and cools, producing rain.

Meanwhile, regions farther from the equator may experience desiccation and lower rainfall due to descending air from high-pressure zones associated with these circulation patterns.

This connection between global circulation patterns and rainfall highlights why it is the most influential factor in determining precipitation, as opposed to local temperature variations, global cooling patterns, or elevation changes, which play significant but more localized or secondary roles in influencing specific weather outcomes.