About 70% of earth is covered with water, most of it being in the ocean.
In the atmosphere, water can be liquid, ice and water vapor
The process of water coming from its liquid state and moving to the atmosphere in
the gas form is called evaporation
Anytime there is any energy evaporation can occur. The more energy, the
more gas molecules that will appear
Condensation is when gas comes out of the air and condenses into liquid
form, or solid form
The balance between these two processes is called saturation.
Evaporation is equal to condensation.
Saturated air does not occur
that frequently. Any additional input of water in a saturated
environment means that there will be some sort of cloud formation.
How do we know that the air is saturated? Cloud or fog formation
How do we know how close we are to saturation?
Due point temperature: hypothetical temperature in the air in which
you would get saturation. The higher the due point temperature is,
the more moisture there is in the air.
The temperature of the air is always greater than or equal to the due
Vapor pressure: pressure exerted by water vapor molecules.
The warmer it is, the more evaporation will take place so there will be a
higher vapor pressure. This is an exponential relationship.
This shows that takes a little extra heat in the air to create a little
extra water vapor.
Warm air promotes more evaporation.
Saturation vapor pressure: max possible water vapor
Ways to describe atmospheric moisture content:
Dew point temperature
The maximum number of water temperature has happened
Max possible: saturation vapor pressure is when the maximum evaporation
Humidity: amount of moisture in the air.
Due point tells us relativity how much moisture is in the air; humidity is the
actual measurement of moisture.
: density of water vapor
This is USELESS and very impractical
: mass of water vapor divided by the mass of all the air
This is a theoretical concept but it is something that we can
calculate, not necessarily measure
The reason that specific humidity is used because it is useful for
comparing humidity at different locations
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: amount of water vapor in the atmosphere compared to
the maximum possible water vapor if the air is saturated
Based on temperature as temperature goes up, the more evaporation
is possible, greater possible water vapor maximum, and relative
humidity goes down
The warmest time of the day has the lowest relative humidity. At the
coldest time (late at night) that is when there is the highest relative
This explains why there is due on the ground and
condensation on cars.
If the relative humidity hits 100%, that means that the air is
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This note was uploaded on 10/11/2011 for the course PSYC, PSYC 2076, 2060 taught by Professor Briganti,gustan,perlis,namikas,wheeler during the Spring '10 term at LSU.