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Chapter 16:

Chapter 16:. Weather. Chapter 16. Understanding Weather. Table of Contents. Section 1 Water in the Air Section 2 Air Masses and Fronts Section 3 Severe Weather Section 4 Forecasting the Weather. Section 1 Water in the Air. Chapter 16. Bellringer.

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Chapter 16:

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  1. Chapter 16: Weather

  2. Chapter 16 Understanding Weather Table of Contents Section 1 Water in the Air Section 2 Air Masses and Fronts Section 3 Severe Weather Section 4 Forecasting the Weather

  3. Section1 Water in the Air Chapter 16 Bellringer • Observe two glasses of water. One filled with ice water, and one filled with warm water. Why do water droplets form on the outside of the cold container? Where do the water beads come from? Why don’t the water beads form on the warm container? • Write your answers in your science journal.

  4. Section1 Water in the Air Chapter 16 Review 2/16/12 • On a separate sheet of paper: • Draw the water cycle and clearly label all the process that occur including what causes them. • Give 2 examples of condensation occurring. • Explain why the water cycle is so important to life on Earth. • T or F, it is possible for water to exist as a solid, liquid, and gas in the atmosphere. • What is humidity? • Why does Minnesota have such high humidity while Arizona has such low humidity? • How are humidity and relative humidity different?

  5. Section1 Water in the Air Chapter 16 Objectives • Explain how water moves through the water cycle. • Describe how relative humidity is affected by temperature and levels of water vapor. • Describe the relationship between dew point and condensation.

  6. Section1 Water in the Air Chapter 16 Objectives, continued • Listthree types of cloud forms. • Identify four kinds of precipitation.

  7. Section1 Water in the Air Chapter 16 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.

  8. Section1 Water in the Air Chapter 16

  9. Section1 Water in the Air Chapter 16 Humidity • Humidityis the amount of water vapor in the air. • The air’s ability to hold water vapor changes as the temperature of the air changes.

  10. actual water vapor content (g/m3)  relative humidity (%) saturation water vapor content (g/m3) Section1 Water in the Air Chapter 16 Humidity, continued • Relative Humidityis the amount of water vapor in the air compared to the maximum amount of water vapor that the air can hold at a certain temperature. • Calculate the relative humidity by using the formula:

  11. Section1 Water in the Air Chapter 16 Humidity, continued • Measuring Relative Humidity A psychrometer is an instrument that is used to measure relative humidity. A psychrometer consists of two thermometers, one of which is a wet-bulb thermometer. • The difference in temperature readings between the thermometers indicates the amount of water vapor in the air.

  12. Section1 Water in the Air Chapter 16 Humidity, continued

  13. Section1 Water in the Air Chapter 16 Condensation • Condensation is the process by which a gas, such as water vapor, becomes a liquid. • Dew Point The dew pointis the temperature at which a gas condenses into a liquid.

  14. Section1 Water in the Air Chapter 16 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.

  15. Section1 Water in the Air Chapter 16 Clouds, continued • Cumulus Cloudsarepuffy, 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.

  16. Section1 Water in the Air Chapter 16

  17. Section1 Water in the Air Chapter 16 Clouds, continued

  18. Section1 Water in the Air Chapter 16 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.

  19. Section1 Water in the Air Chapter 16 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

  20. Section2 Air Masses and Fronts Chapter 16 Bellringer • Think of as many different qualities of air as possible. • Write your answers in your science journal.

  21. Section2 Air Masses and Fronts Chapter 16 Objectives • Identifythe four kinds of air masses that influence weather in the United States. • Describe the four major types of fronts. • Explain how fronts cause weather changes. • Explain how cyclones and anticyclones affect the weather.

  22. Section2 Air Masses and Fronts Chapter 16 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.

  23. Section2 Air Masses and Fronts Chapter 16 Air Masses, continued • Warm Air Masses Four warm air masses influence the weather in the United States.

  24. Section2 Air Masses and Fronts Chapter 16 Fronts • The area in which two types of air masses meet is called afront. • Cold Fronts A cold front forms where cold air moves under warm air, which is less dense, and pushes the warm air up. • Warm FrontsA warm front forms where warm air moves over cold, denser air.

  25. Section2 Air Masses and Fronts Chapter 16

  26. Section2 Air Masses and Fronts Chapter 16 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.

  27. Section2 Air Masses and Fronts Chapter 16

  28. Section2 Air Masses and Fronts Chapter 16 Air Pressure and Weather • Cyclones are areas that have lower pressure than the surrounding areas do. • Anticyclonesare areas that have high pressure.

  29. Section3 Severe Weather Chapter 16 Bellringer • Write a one-paragraph description of a thunderstorm. Describe the weather conditions immediately before, during, and after the storm. How does the storm affect each of your senses? • Record your response in your science journal.

  30. Section3 Severe Weather Chapter 16 Objectives • Describe how lightning forms. • Describe the formation of thunderstorms, tornadoes, and hurricanes. • Describethe characteristics of thunderstorms, tornadoes, and hurricanes. • Explain how to stay safe during severe weather.

  31. Section3 Severe Weather Chapter 16 Severe Weather • Is weather that can cause property damage and sometimes death. • Thunderstorms are small, intense weather systems that produce strong winds, heavy rain, lightning, and thunder. • 2 things required for thunderstorms to occur: • Warm moist air near Earth’s surface • Unstable atmosphere

  32. Section3 Severe Weather Chapter 16 Severe Weather • Atmosphere is unstable when surrounding air is colder than the rising air mass. • When the rising air reaches its dew point the vapor condenses forming a cumulous cloud. • In extremely unstable air the warm air continues to rise creating a large, dark, cumulonimbus cloud. (15 km high)

  33. Section3 Severe Weather Chapter 16 Lightning • Lightning is an electrical discharge that occurs between a positively charged area and a negatively charged area. • An electrical charge builds up due to friction between moving particles in a cloud. • Those charges separate from one another, which eventually leads to an electrical discharge (lightning). • Thunderis the sound that results from the rapid expansion of air around a lightning strike.

  34. Section3 Severe Weather Chapter 16 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

  35. Section3 Severe Weather Chapter 16 Tornadoes • A tornado is a small, spinning column of air that has high wind speeds and low central pressure and that touches the ground. • It happens in only 1% of all thunderstorms.

  36. Section3 Severe Weather Chapter 16 Tornadoes • How it forms: • Wind moving in two directions causes a layer of air to begin to spin. • Strong updrafts of air turn the spinning column of air vertically. • The spinning column begins to move downward forming a funnel cloud. • The funnel cloud becomes a tornado when it touches the ground.

  37. Section3 Severe Weather Chapter 16 Tornadoes, continued

  38. Section3 Severe Weather Chapter 16 Tornadoes • About 75% of all tornados occur in the U.S. • Most happen in the spring and early summer. • Cold dry air from Canada meets warm moist air from the tropics. • Average wind speed is 120 to 180 km/hr, but some can reach speeds of 500 km/hr.

  39. Section3 Severe Weather Chapter 16 Hurricanes • A large tropical weather system that has wind speeds of at least 120 km/hr is called a hurricane (aka typhoons and cyclones). • Size can be 160 to 1,500 km/hr

  40. Section3 Severe Weather Chapter 16 Hurricanes • Hurricane formation: • Only in the warmer parts of the ocean • Two thunderstorms moving in opposite directions meet and start to spin • Gets its energy from the condensation of water vapor • Hurricane is fueled by warm water. • Hurricanes die out when they reach land or cooler ocean waters

  41. Section3 Severe Weather Chapter 16 Hurricanes • Parts of a hurricane: • Eye – The calm, warm, center of a hurricane • Eyewall– Surrounds the eye and is made up of large cumulonimbus clouds with heavy rains and strong winds (300 km/hr) • RainBands– Outside the eye wall. The wind speed and rain decrease as the rain bands move outward from the eye wall.

  42. Section3 Severe Weather Chapter 16 Hurricanes, continued

  43. Section3 Severe Weather Chapter 16 Hurricanes • Hurricanes can cause a great deal of damaged due to high winds and flooding. • A storm surgeis a wall of water that builds up at a hurricane and can cause flooding as a hurricane hits the shore.

  44. Section3 Severe Weather Chapter 16 Severe Weather Safety • Thunderstorm Safety Lightning is one of the most dangerous parts of a thunderstorm. If you are outside, stay away from trees, which can get struck down. If you are in the open, crouch down. • Tornado Safety If there is a tornado warning for your area, find shelter quickly. The best place to go is a basement or cellar.

  45. Section3 Severe Weather Chapter 16 Severe Weather Safety, continued • Flood SafetyThe best thing to do during a flood is to find a high place to wait out the flood. • Hurricane Safety If you live in an area where hurricanes strike, your family should have a disaster supply kit that includes enough water and food to last several days.

  46. Section3 Severe Weather Chapter 16 Review What are the three parts of a hurricane? Why do most tornados occur during the spring and early summer? How fast do winds have to be moving for a tropical storm to be considered a hurricane? What provides the energy for hurricanes? What creates the electric charge separation in storm clouds. What two things are required for thunderstorms to occur? The strength of a storm is determined by what?

  47. Section4 Forecasting the Weather Chapter 16 Bellringer • If you did not have the benefit of the weather forecast on the news, radio, or television, how would you forecast the weather? • Record your answer in your science journal.

  48. Section4 Forecasting the Weather Chapter 16 Objectives • Describe the different types of instruments used to take weather measurements. • Explainhow radar and weather satellites help meteorologists forecast the weather. • Explain how to interpret a weather map.

  49. Section4 Forecasting the Weather Chapter 16 Weather-Forecasting Technology • High in the Sky Weather balloons carry electronic equipment that can measure weather conditions as high as 30 km above Earth’s surface. • Measuring Air Temperature and Pressure A tool used to measure air temperature is called a thermometer. An instrument used to measure air pressure is a barometer.

  50. Section4 Forecasting the Weather Chapter 16 Barometer

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