Do clouds float on anything?

Question

Clouds of the same type have such a consistent altitude, it appears as if they're floating on an invisible layer. Is this true? Put another way, is there a significant change in air composition at the point where clouds float/form, or is that altitude determined primarily by air pressure?

Answer 1

Clouds just float in the air. Clouds form when air is warmer than its surroundings. The air then cools as it rises. It eventually cools to its dew point, forming a cloud.

Pressure does decrease with altitude as there is less weight on air the higher up it is.

Answer 2

Clouds form in response to temperature and pressure, which in turn are functions of wind speed--both horizontal and vertical.

In the simplest case, air rises** until the temperature is at the dew point. Then the water vapor turns to liquid water, and you have a cloud.

**air that is warmer than the surrounding parcels rises in relation to those parcels.