1. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Water in the Air Bellringer What causes wind? Write your answers in your science journal. Chapter I2

2. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Water in the Air Bellringer How do clouds form? Write your answers in your science journal. Chapter I2

3. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Water in the Air Do now? If a cold air mass meets a warm air mass full of moist air, the cold air will sink and push the warm air upwards. When this happens, energy will be removed from the warm air. As the energy is removed, what will happen to the water in the air? Write your answers in your science journal. Chapter I2

4. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu

5. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Water in the Air Objectives 1. Describe how relative humidity is affected by temperature and levels of water vapor. 2. List three types of cloud forms. 3. Identify the four kinds of air masses that influence weather in the United States. 4. Describe the four major types of fronts. Chapter I2

6. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Agenda Today we will: –Learn about weather by reading, discussion and investigation –Do now –Notes –Reading –Exit ticket

7. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Water in the Air Vocabulary weather humidity cloud air mass front

8. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Water in the Air The Water Cycle The condition of the atmosphere is affected by the amount of water in the air. Water in liquid, solid, and gaseous states is constantly being recycled through the water cycle. The water cycle is the continuous movement of water from sources on Earth’s surface into the air, onto and over land, into the ground, and back to the surface. Chapter I2

9. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Water in the Air Humidity Humidity is the amount of water vapor in the air. The air’s ability to hold water vapor changes as the temperature of the air changes. Chapter I2

10. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Water in the Air Condensation Condensation is the process by which a gas, such as water vapor, becomes a liquid. Dew Point The dew point is the temperature at which a gas condenses into a liquid. Chapter I2

11. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Water in the Air Clouds A cloud is a collection of small water droplets or ice crystals suspended in the air, which forms when the air is cooled and condensation occurs. Clouds are classified by form, and by altitude. Chapter I2

12. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Water in the Air Clouds, continued Cumulus Clouds are puffy, white clouds that tend to have flat bottoms. Stratus Clouds are clouds that form in layers. Cirrus Clouds are thin, feathery, white clouds found at high altitudes. Chapter I2

13. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Water in the Air Chapter I2

14. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Water in the Air Clouds, continued Chapter I2

15. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Water in the Air Precipitation Rain is the most common form of precipitation. Sleet and Snow Sleet forms when rain falls through a layer of freezing air. Snow forms when temperatures are so cold that water vapor changes directly to a solid. Hail are balls or lumps of ice that fall from clouds. Chapter I2

16. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Water in the Air Formation of Clouds and Precipitation Click below to watch the Visual Concept. You may stop the video at any time by pressing the Esc key. Visual Concept Chapter I2

17. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 Air Masses and Fronts Air Masses Changes in weather are caused by the movement and interaction of air masses. An air mass is a large body of air where temperature and moisture content are constant throughout. Cold Air Masses Most of the cold winter weather in the United States is influenced by three polar air masses. Chapter I2

18. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 Air Masses and Fronts Air Masses, continued Warm Air Masses Four warm air masses influence the weather in the United States. Chapter I2

19. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 Air Masses and Fronts Fronts The area in which two types of air masses meet is called a front. Cold Fronts A cold front forms where cold air moves under warm air,which is less dense, and pushes the warm air up. Warm Fronts A warm front forms where warm air moves over cold, denser air. Chapter I2

20. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 Air Masses and Fronts Chapter I2

21. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 Air Masses and Fronts Fronts, continued Occluded Front An occluded front forms when a warm air mass is caught between two colder air masses. An occluded front has cool temperatures and large amounts of rain and snow. Stationary Front A stationary front forms when a cold air mass meets a warm air mass. A stationary front often brings many days of cloudy, wet weather. Chapter I2

22. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 Air Masses and Fronts Chapter I2

23. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Severe Weather Thunderstorms Lightning is an electric discharge that occurs between a positively charged area and a negatively charged area. Thunderstorms are very active electrically. Thunder is the sound that results from the rapid expansion of air along the lightning strike. Chapter I2

24. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Severe Weather Lightning and Thunder Click below to watch the Visual Concept. You may stop the video at any time by pressing the Esc key. Visual Concept Chapter I2

25. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Severe Weather Tornadoes A tornado is a small, spinning column of air that has high wind speeds and low central pressure and that touches the ground. A tornado starts out as a funnel cloud that pokes through the bottom of a cumulonimbus cloud and hangs in the air. The funnel cloud becomes a tornado when it makes contact with Earth’s surface. Chapter I2

26. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Severe Weather Tornadoes, continued Chapter I2

27. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Severe Weather Hurricanes How a Hurricane Forms A hurricane begins as a group of thunderstorms moving over tropical ocean waters. Winds traveling in two different directions meet and cause the storm to spin. Damage Caused by Hurricanes Hurricanes can cause a lot of damage when they move near or onto land. Wind speeds of most hurricanes range from 120 to 150 km/h. Chapter I2

28. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Severe Weather Hurricanes, continued Chapter I2

29. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Exit Ticket What are fronts and air masses and how do they influence weather?