Date post: | 30-Dec-2015 |
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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?