Which is NOT a method for cloud formation?

Cloud formation involves various processes that cause water vapor in the atmosphere to condense into tiny droplets or ice crystals, forming clouds. The option stating that "air warmed by sunlight" is not a method for cloud formation is correct because the warming of air typically generates convection and stability, which can inhibit cloud formation rather than promote it.

In contrast, lifting mechanisms, such as cold air being pushed upward, facilitate the cooling of air as it ascends, allowing moisture to condense and form clouds. Similarly, when air moves over a cold surface, it can lose heat, leading to condensation if the temperature drops sufficiently. Air cooled by radiation can also lead to cloud formation, particularly during nighttime when surface temperatures drop, causing the air near the ground to cool and condense moisture.

Warming air by sunlight usually leads to increased buoyancy and movement upward, resulting in clearer skies, as the warmed air can hold more moisture in vapor form without condensation occurring. Thus, while warming air is essential in the weather system overall, it does not directly lead to cloud formation.