Relative HumidityIs how much moisture a given mass of air is holding compared to how much water

that air is capable of holding expressed as a percent.

What % full?

What would happen to that % if the same water were in a smaller glass?

How to measure humidity -

Sling Psychrometer• Remember -

evaporation cools things (sweat, misters in outdoor cafes, etc.)

• Evaporation goes faster in dry air.

• The drier the air - the greater the difference between wet and dry-bulb temperatures.

Hair Hygrometer -• Hair changes length depending on

humidity - “bad hair days”!

Cold is air’s kryptonite

• Warm air can hold more moisture.• Cold air holds less moisture.• So, cooling air reduces the air’s ability

to hold moisture, and if that air was holding a lot of moisture, it may drop moisture (condensation).

• What happens to RH if you warm the air?

Dew point -• The temperature that you have to cool air to in

order to make the air drop its moisture is the dew point.

• RH = 100% at DP.• Is dew point high or low on a dry day?

If you cool air to its dew point, condensation happens.

• If you breathe on cold glass, moisture from your breath ____________ on the glass.

• If you cool air up in the sky to its dew point, water vapor condenses into ___________.

• If you cool air near ground level to its dew point, ______ forms.

• On cool mornings, _____ forms on cool grass.• If the dew point is below freezing (32f or 0c)

and the air gets that cold , _______ would form on grass instead of dew.

Why do clouds have flat bottoms?