1. Weather Conditions

2. What Makes up Earth’s Atmosphere? • The layer of air surrounds our planet is called the atmosphere.

3. Layers of the Atmosphere • Troposphere • Stratosphere • Mesosphere • Thermosphere

4. Troposphere • Layer closes to the earth • Weather happens in this layer • Live and breathe air in this layer • Air temperature decreases as you go higher

5. Stratosphere • Airplanes travel in this layer to avoid bad weather • Contains most of the atmosphere’s ozone • Ozone protects living things from harmful rays of the sun • Temperature increase with height

6. Mesosphere • Temperature decrease with height • Coldest layer of the atmosphere

7. Thermosphere • Hot, outermost layer • Temperature increase quickly with height

8. How Do Air Masses Affect the Weather

9. Greenhouse Effect

10. Air Masses

11. What happens when to air masses meet? • When two air masses meet, they form a border called a front • A front is the area where two air masses meet and weather happens

12. Cold Front • A cold air mass catches up with a warm air mass • The cold air mass forces the warm air up in the atmosphere • As warm air

13. Cold Front • As warm air pushes upward, it cool and forms cloud. • Rain develops. • Thunderstorm often occur along a cold front.

14. Cold Front • Generally move from northwest to southeast • Air behind a cold front is colder and drier than the air ahead of it. • When a cold front passes through, temperatures can drop more than 15 degrees within the first hour. • Represented by a solid lines with triangles along the front pointing towards the warmer air and in the direction of movement

16. Warm Front • Forms when a warm air mass catches up with a cold air mass • Warm air slides up over the colder, denser air

17. Generally move from southwest to northeast • Air behind a warm front is warmer and more moist than the air ahead of it

18. Represented by a solid line with semicircles pointing towards the colder air and in the direction of the movement • Steady rain or snow may fall as the front approaches and passes

19. Common Characteristics of Warm Fronts

21. Clouds and Weather • Weather scientists classify a cloud based on its shape, its color, and where it forms in the atmosphere

22. Cirrus • A wispy white cloud • Fair weather

23. Cumulus • Puffy cotton-ball clouds • Begins to form when water droplets condense at middle altitudes

24. Cumulonimbus • Dense cumulus cloud with a hazy outline • Usually producing heavy rain, thunderstorms, or hailstorms

25. Stratus • Dark gray clouds that form a low layer • Sometimes bring rain or snow showers

26. What is a Cycle? • A sequence of events that repeat themselves

27. Evaporation • The sun heats up water in rivers, lakes, or ocean • The water changes from a liquid into a gas, vapor, or steam. • The water vapor leaves the rivers, oceans, or lakes and goes into the atmosphere.

28. Condensation • Water vapor in the air gets cold and changes back into liquid • forming clouds

29. Transpiration • Is the process by which plants return water to the atmosphere. • After absorbing water from the ground, plant release water through their leaves. • This helps plants stay cool.

30. Precipitation • Occurs when so much water has condensed that the air cannot hold it anymore. • Clouds get heavy and water falls back to earth in the form of rain, sleet, hail, or snow

31. What instruments do meteorologist use to forecast weather?

32. Anemometer • Measures wind speed • The cups catch the wind, turning a dial attached to the instrument. • The dial shows the wind speed.

33. Barometer • Measures air pressure

34. Psychrometer • Measures relative humidity, using the cooling effect of evaporation

35. Hygrometer • Measures the amount of humidity in the air.