1. Water in the Atmosphere

2. Water in the Atmosphere
The Water Cycle

3. Humidity
Humidity is a measure of the amount of water vapor in the air.
The amount of water vapor that the air can hold depends on its temperature.
Warm air can hold more water vapor than cool air.

4. Humidity
The percentage of water vapor in the air compared to the maximum amount the air could hold is called the relative humidity.

5. Relative humidity can be measured using a psychrometer.

6. Water in the Air
Clouds form when water vapor in the air becomes liquid water or ice crystals.
The process by which molecules of water vapor in the air become liquid water is called condensation.

7. Water in the Air
The temperature at which condensation begins is called the dew point.
Clouds form whenever air is cooled to its dew point and particles are present.

8. Types of Clouds
Meteorologists classify clouds into three main types (shapes):
1. Cumulus
2. Stratus
3. Cirrus
Clouds are also classified by their altitude.
Each type of cloud is associated with a different type of weather.

9. Cumulus
Clouds that look like fluffy, rounded piles of cotton are called cumulus clouds.
Cumulus clouds usually indicate fair weather.
Towering clouds with flat tops, called cumulonimbus clouds, often produce thunderstorms.

10. Stratus Clouds that form in flat layers are called stratus clouds.
As stratus clouds thicken, they may produce drizzle, rain, or snow.
They are then called nimbostratus clouds.

11. Cirrus Wispy, feathery clouds are called cirrus clouds.
Cirrus clouds form only at high levels, where temperatures are very low.
As a result, cirrus clouds are made of ice crystals.
Cirrocumulus clouds often indicate that a storm is on its way.

12. Lenticular Clouds
Air gets pushed upward where it cools and condenses into clouds. 
Depending on how smooth the flow is, you can get some amazing clouds formations

13. Mammatus Clouds

14. Clouds that form at or near the ground are called fog
Fog often forms when the ground cools at night after a warm, humid day