1. Weather and Climate

2. Weather The present state of the atmosphere
Describes current conditions
Caused by interactions of heat energy, air pressure, winds, and moisture

3. Heat Energy
The sun’s energy that is absorbed by the Earth is spread throughout the atmosphere

4. Air Pressure
The air pressure at any particular point on Earth depends on the density of the air.
Denser air exerts more air pressure

5. Winds
Both local winds and global winds are caused by differences in air pressure due to unequal heating of the atmosphere.

6. Moisture in the Air
Water vapor, or moisture, in the air is called humidity.

7. Humidity changes with temperature
Cooler temperature = less water vapor = lower humidity
Warmer temperature = more water vapor = higher humidity

8. Relative Humidity
The percent of moisture the air holds relative to the amount it could hold at a particular temperature.
Ex – at a certain temperature, 1kg of air can hold 12g of water vapor. It is actually holding 9g of moisture.What is the relative humidity?

9. Relative Humidity
100% relative humidity means that air is holding as much moisture as it can hold and is saturated.

10. Dew Point
The temperature at which air is saturated and condenses

11. Clouds
Clouds form when moisture in the air condenses on small particles of dust or other solids in the air

12. Cloud Classification
Classified by shape and height

13. Cloud Shapes
3 main types of cloud
Stratus
Cumulus
Cirrus

14. Stratus
Smooth, gray clouds that cover the whole sky and block the sun.
Form at low altitudes
Associated with light rain and drizzle
When stratus clouds form close to the ground the result is fog.

16. Cumulus Look like piles of cotton balls in the sky
Are fluffy white with flat bottoms
Tower to great heights
Usually indicate fair weather

18. Cirrus Feathery or fibrous clouds Sometimes called mare’s tails
From at very high altitudes
Made of ice crystals
Can be seen in fair weather but often indicate rain or snow is expected in several hours.

20. Cloud Height Prefixes of cloud names describe height of the cloud base
Cirro = high clouds
Alto = middle elevation
Strato = low clouds

21. Shape names can also prefixes to describe clouds
Nimbostratus clouds bring rain and snow
Cumulonimbus clouds are dark at the bottom and produce thunderstorms.

22. Precipitation
Water vapor that condenses and forms clouds can fall to Earth as rain, sleet, snow, or hail.
Water that falls from the atmosphere to the Earth is called precipitation.

23. Precipitation Air temperature determines the form Warm air = rain
Cold air = snow
Warm air then cold air = sleet
Water droplets moving up and down in the cloud before falling in warm air =hail