1. The Formation of Clouds

2. The Formation of Clouds
As weather changes from day to day, so do the clouds. Some clouds are puffy and tall, while others are layered and flat. Some clouds are found at high elevations and are made of ice crystals and other clouds are found at low elevations and are made of water droplets. Some clouds are associated with rain and storms while others are associated with good weather.

3. Essential Questions
What ingredients are necessary for clouds to form?
Why do clouds form at different heights?
What is fog and how does it form?
What causes air to rise, cool and form clouds? (there are 4 ways!)

4. Goals: You should be able to…
Describe how the formation of clouds is influenced by the dew point, temperature and amount of particles in the air.
Describe 4 ways air is lifted for clouds to form.
Describe how air pressure and temperature change with increasing altitude and/or latitude.
Observe, measure, and predict changes in weather using atmospheric properties (cloud cover and type along with other weather data).

5. The Formation of Clouds
The three ingredients needed to form clouds are:
Warm, moist air
Cool air
Small pieces of matter, such as dust, smoke, or other microscopic particles

6. The Formation of Clouds
Condensation is the process by which water vapor changes into liquid droplets.
Question: When does condensation happen?
Condensation will happen when the air reaches its dew point temperature.
This means the air cools down to a point where it cannot hold any more water vapor.

7. The Formation of Clouds
In general, as altitude increases, air temperature and air pressure decrease.
The dew point is the temperature that air must reach for water vapor to turn into liquid water.
Question: Why does this happen?
This means the air cools down to a point where it cannot hold any more water vapor. (Cold air cannot hold as much water vapor as warm air.)

8. The Formation of Clouds
When the warm air rises and cools, the amount of water vapor needed for saturation decreases.
Question 1: Why does warm air rise?
Question 2: Why does the amount of water vapor needed for saturation decrease?

9. The Formation of Clouds
When this warm, moist air rises and reaches dew point, the water vapor will condense into tiny water droplets on microscopic pieces of matter (such as dust). Billions of these water droplets form a cloud.

10. The Formation of Clouds
Question: With the information you have, explain why different clouds form at different heights.
The height of a cloud formation is determined by the point where the warm, moist air reaches dew point temperature in the atmosphere.

11. The Formation of Clouds
The shape and height of any given cloud varies with pressure, temperature, and the amount of water vapor in the atmosphere.

12. The Formation of Clouds
Question: What will form when air is cooled to its dew point near the ground?
When air is cooled to its dew point near the ground, it forms fog (a low stratus cloud).

13. The Formation of Clouds
Air can be lifted up in the atmosphere due to:
Convection
Topography
Convergence
Frontal activity