When you help someone up a hill, you get that much closer to the top yourself. -Anonymous
Question #92433 posted on 07/07/2019 noon

Dear 100 Hour Board,

Hot air rises over cool air. But does humid air rise or fall particularly, given the same temperature?



Dear Arn,

So the principle in hot air rising over cold air is that hot air is less dense than cool air. This causes it to sink and the warmer air to rise. Humidity is a measure of the amount of water vapor in the air. More humid air has more water molecules, which you would think makes the air heaver, but it actually makes it lighter. Water molecules way less than the N2 and O2 molecules that make up most of the atmosphere, and increasing humidity pushes those molecules and makes the air less dense and thus, lighter. In a surprising turn of events more humid air rises and drier air sinks.