1. Chapter 2: Understanding Weather
Section 1:
Water in the Air

2. The Water Cycle – the continuous
movement of water from Earth’s ______
& _____ into the __________, in the
______, and back into the ______ &
_____
oceans
rivers
atmosphere
ground
oceans
rivers

3. - Humidity
* Amount of __________ in the air
* As the __________ increases so does
the air’s ability to hold water vapor
water vapor
temperature

4. Relative Humidity – measures the amount
of __________ in the air compared with
the _________ amount of water vapor that
the air can hold at a certain temperature
* Measured using a ____________
water vapor
maximum
psychrometer

5. Condensation – process by which a gas
(water vapor) becomes a liquid (water)
* The air must be ________ (100%
relative humidity)
* Can also occur when air cools to its
________ (the temperature at which
gas becomes a _____)
saturated
dew point
liquid

6. Clouds – a collection of small water droplets
or ice crystals suspended in the air
- Cumulus – puffy, white clouds that tend
to have flat bottoms

7. - ______ – form in layers & cover large
areas of the sky & often block out the sun
(____ is a stratus cloud that has formed
near the ground)
Stratus
Fog

8. - Cirrus – thin, feathery clouds found at high
altitudes

9. - Nimbo – or – nimbus indicate clouds that
are likely to form __________
precipitation

10. - Cirro – clouds formed at high altitudes
- Alto – clouds formed at middle altitudes

11. Precipitation – when water returns to Earth’s
surface
- Rain – most common
- _____ – rain falls through freezing air &
freezes into ice
- _____ – air is so cold that the water
vapor freezes directly into ice
Sleet
Snow

12. - Hail – forms when raindrops are caught in
an updraft & are carried into higher clouds
where it freezes. As it starts to fall more
water vapor attaches to the ice. The ice
may be caught in another updraft & the
outer water vapor freezes. This happens
again & again until the ice ball is too heavy
to be lifted by an updraft. The largest
hailstone ever recorded was the size of a
softball

14. Let’s Review
Weather is the condition of the atmosphere at a certain time and place. Weather is affected by the amount of water vapor in the air.
The water cycle describes the movement of water above, on, and below Earth’s surface.
Humidity describes the amount of water vapor in the air. Relative humidity is a way to express humidity.
When the temperature of the air cools to its dew point, the air has reached saturation and condensation occurs.
Clouds form as air cools to its dew point. Clouds are classified by form and by the altitude at which they form.
Precipitation occurs when the water vapor that condenses in the atmosphere falls back to Earth in solid or liquid form.