Why does higher dew point indicate more water vapour molecules in the air?
In: Physics
Let’s talk about dew first, for a second. Warmer air can hold more moisture, cooler air holds less, so if you have air with some water vapor in it, and you cool it down, its “vapor capacity” will fall until it hits a point where it can *just barely* hold all the water vapor it has. That’s called the saturation point or the dew point.
If you cool it a tiny bit more than that, water vapor starts to condense and dew droplets form.
If air is really really moist, it starts out close to its limit and you only have to cool it a little bit before it saturates. It hits saturation while still warm, in other words it reaches its dew point at a high temperature; in short, moist air = high dew point.
If air has very little moisture in it, you can cool it a whole bunch and it can still hold that bit of moisture no problem. You have to get it really cold before condensation happens. In other words it reaches its dew point at a really low/cold temperature. Dry air = low dew point.
(Is that what you were asking? I’m not totally sure I covered the part that was bugging you.)
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