Like what is the difference between cold and warm air besides the temperature, and why does the temperature matter?
In: Planetary Science
Water evaporates more as it gets warmer. If air gets cold, the water it contains also gets cold and starts turning liquid (dew). This leaves less water in the air.
Simply put, warm air means that water molecules in that air have a higher amount of energy. In cold air, the water molecules move slower and then condense into liquid or ice.
More energy water molecules = gas
Low energy = water/ice
It’s all about temperature. Hot = molecules moving faster. The faster water molecules move, the more they fly into the air. The slower they move, the more likely they are to fall and be liquid, and less likely to fly into the air in the first place.
This idea is called vapor pressure.
At the most basic level, higher temperatures make water molecules more excited, so they’re more likely to jump to the vapor phase (basically just evaporation) and the air molecules are farther apart, so there’s more room for the water to go.
The fancy word for this is psychrometrics. It’s a property of air and relates the temperature of the air to how much water it can hold. That amount of water in the air is called humidity and can be measured as either absolute humidity (the total amount of water in the air) or relative humidity (which is the percentage of how much water is in the air compared the maximum amount it can hold). In general, the air wants to hold about half as much water as it’s capable of (50% relative humidity). When it’s really cold, that amount of water is really low. As the air warms up, when it’s in your lings for instance), the heirs capacity to hold water goes up, but there’s still the same amount of water, so the relative humidity goes down. This causes the air to suck up water and dry out anything wet it touches.
You can imagine air like a bunch of little balls representing the molecules.
Warm air has those balls moving around faster. Part of the warmth is from those tiny air molecules ramming into things. Faster molecules can ram into things and keep more energy. Faster molecules also have more “space” between them. That’s more room for water.
Part of how water gets into air is those air molecules slam into water so hard it dislodges one of the water molecules and carries it away. That water molecule would *really* like to find other water molecules, join them again, then be a liquid. But if air molecules keep smacking into it, they’ll keep knocking it away from other water molecules so it can’t.
The faster the air molecules are moving, the more water molecules they can smack around and stop from forming into liquid again. It kind of works both ways, too: if hot air meets cold water the area around the water ends up as very humid but also much colder air. This is sort of why convection ovens cook differently than normal ovens but that’s a different question!
Hot molecule go buzz. Cold molecule go slow and sticky. That’s why condensation forms on cold objects. It gets slow and sticks to the cold object.
It’s not a moisture vacuum. It actually doesn’t suck up any more water, or at a faster rate than hot air. Yep. What it does do is evaporate water at a slower rate than hot air.
Cold air does not “hold” any more moisture than hot air. It’s just that there is constantly water being absorbed into the air and there is always water condensing out of the air. The rate of condensation is a function of how much energy the water molecules have which is related to their temperature. Hotter air = less energy and slower condensation. So, water tends to get driven out of hot air more than cold.
Like I’m five… Cold air has less thermal energy to drive water out.
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