1. Water in the Air Section 1
Understanding Weather
Chapter 15

2. The Water cycle
The continuous changing of water from a liquid to a solid or gas, and back to a liquid.
The main parts of the cycle are…
-Evaporation
-Condensation
-Precipitation

4. Humidity Humidity is the amount of water or moisture in the air.
Not all Air can contain the same amount of water…
The warmer air is, the more water vapor it can hold.
The cooler air is the less water it can hold.

6. Relative Humidity
This is the amount of water the air is caring as a Percent of what it can actually carry.
Remember, all air can carry 100%, this is called saturated air (it could not possibly hold any more)
If our room is 80º and Mr. Perez’s room is 85º and the air is saturated in both, what room will have more water?

7. The process of condensation
Condensation is the process in which water vapor changes back into a liquid, this may happen in two ways.
1) the air is saturated and can hold no more water vapor, so it transforms into a liquid again.
2) the air contains water vapor (only 80%), the temperature decreases, and now that it can’t hold as much water, it is at 100% humidity.

9. Clouds
Clouds are a collection of millions of tiny water droplets, or ice crystals.
Clouds form when warm air rises and cools, causing condensation.
In order for water vapor to form a water drop, it needs something to attach itself to.
This is called condensation nuclei, and it can be dust, smoke or salt that is floating in the air.

12. Types of clouds Three main types of clouds…
Cumulus: Big puffy white clouds
Stratus clouds: large blanket-like clouds.
Cirrus clouds: thin feathery clouds
If the cloud name also contains the words nimbo or nimbus, this means that it will rain.

13. Cumulus clouds Large puffy cotton candy looking.
These clouds form when warm air rises.
These clouds signify good weather, but when they get too big and change color (gray) they mean rain!

16. Stratus clouds These clouds look like large blankets in the sky.
They block out the sun.
Are caused by gentle lifting of large bodies of air into the atmosphere.

19. Cirrus clouds Very thin clouds Form in very high altitudes
Caused by strong winds

21. Precipitation Water that fall to the ground is called precipitation.
There are four main type of precipitation.
-rain, snow, sleet, and hail.

22. rain This is the most common type of precipitation.
A water droplet usually starts at about the size of a period at the end of a sentence, and may get up to 100 times bigger before it falls

24. Snow
Snow is precipitation that freezes directly from a gas and fall to the ground.

26. sleet
Rain that falls through a layer of freezing air and becomes a solid

28. hail
Rain that falls through a layer of freezing air and becomes a solid, then is pushed back up into the clouds by strong winds.
It falls again and gets wet, and freezes even bigger.
This may happen many times, that’s why hail may be as small as a pea or as big as a golf ball.