What is relative humidity?

1
Lesson 20 What is relative humidity?
2
Fill a large pan with water, and place a sponge
in it. What happens?
Does the sponge soak up all the water?
No, it soaks up water until it is full.
3
When a sponge cannot soak up any more water, we
say it is saturated.
4
The air is like a sponge. Air can hold water.
Water in the air is in gas form, called water
vapor.
The amount of water vapor in the air does not
stay the same.
5
Sometimes, the air has only a small amount of
water vapor, sometimes, it has a lot.
The air can only hold a certain amount of water
vapor. When there is more than that, there is
precipitation.
6
The amount of water vapor the air can hold
depends on the temperature.
Warm air can hold more water vapor than cold air.

The higher the temperature, the more water vapor
the air can hold.
7
Relative humidity tells us how full the air is
with water vapor.
8
Relative humidity compares
-the amount of water vapor in the air
-the amount of water vapor the air can hold
9
Relative humidity is written as a percent ()
The relative humidity of saturated air is one
hundred percent (100)
Saturated air has all the water vapor it can
hold.
10
The relative humidity is 50 when the air holds
only half the water vapor it can hold.
Relative humidity can be very low. It can reach
near 0 but NEVER can be 0.
Even the driest air has some water vapor.
11
B
A
C
Think of the dots as water vapor. Which box of
air has the highest relative humidity?
Which has the least?
12
(No Transcript)