Chapter 17 7th es
- 2. AIR MASSES • A large body of air (thousands of miles) • Changes in weather are caused by movements of air masses • As an air mass moves away, temp & humidity change.
- 4. Classification • Air masses are named from the area where they come from. • Classified according to : temperature & moisture content.
- 5. • Tropical- HOT air mass formed in tropics • Polar- COLD air mass formed near poles • Maritime- air mass formed over oceans, WET • Continental- air mass formed over land, DRY
- 6. TYPES OF AIR MASSES 1. MARITIME TROPICAL 2. MARITIME POLAR 3. CONTINENTAL POLAR 4. CONTINENTAL TROPICAL
- 7. Warm, humid air mass formed over ocean near equator. Summer = hot humid weather Winter = heavy rain/snowfall
- 8. Cool, humid air masses formed over ocean near poles Summer = cool temps, fog, rain Winter = snow, cold temps
- 9. • Hot, dry air masses formed mostly in the summer over dry lands of SW & N Mexico.
- 10. Large, cold air mass formed over land in Canada & Alaska. Winter- extremely cold, dry air. Summer- cold, dry air temps
- 11. • Prevailing Westerlies push air masses west to east. • Jet Stream- blow west to east • Fronts- boundaries between air masses, changeable weather & storms develop along fronts.
- 12. Chapter 17 Lesson 1Review page 581 • What are the two characteristics of an air mass that you need to know in order to classify it? • What happens when a warmer air mass pushes a cooler air mass? • What type of weather system brings calm, clear weather?
- 13. • Colliding air masses can form 4 types of fronts: 1. Cold fronts 2. Warm fronts 3. Stationary fronts 4. Occluded fronts
- 14. • forms when a cold air mass meets & pushes under a warm air mass. • Warm air cools, clouds form, & heavy rain. (thunderstorms). • cool weather
- 16. • Forms when a warm air mass moves over a cold air mass. • Rain showers then hot, humid weather.
- 17. • Warm air mass meets a cold air mass & no movement occurs. Produces rain & clouds.
- 18. • When a warm air mass is caught between 2 colder air masses. Warm air cut off. • Produces clouds, rain/snow.
- 19. • A center of low air pressure, winds spiral inward. • As air rises in a cyclone, the air cools forming clouds & precipitation.
- 20. •High pressure areas of dry air where winds spiral outward. (clockwise) •Descending air in an anticyclone causes dry, clear weather.
- 22. STORM • A violent disturbance in the atmosphere
- 23. • A small storm often accompanied with heavy precipitation & thunder & lightning. • Form in large cumulonimbus clouds called thunderheads.
- 24. • On hot, humid days, warm air rises rapidly, & cools forming cumulonimbus clouds. • This movement of air creates updraft & downdraft winds.
- 25. Areas of (+)/(-) charges build up in storm clouds. It is a sudden discharge of electricity between 2 clouds or the cloud and the ground. Electric energy is released.
- 26. Light travels faster than sound. Lightning heats air. Heated air expands rapidly which results in sound waves (thunder).
- 27. T-Storm Damage • Heavy rains which can lead to floods. • Lightning, Hail, & winds can cause damage.
- 28. • Whirling, funnel shaped cloud that reaches down from a storm cloud to touch earth’s surface. • Warmth & Moisture feed it • Season: late spring/early summer
- 29. • Warm, humid air meets cold, dry air. A squall line of thunderstorms develop which can develop into a tornado. • Warm air rises rapidly & begins to rotate. The cloud will then start to descend to earth in a funnel.
- 30. • Tornado Alley- Mid-West US • This is where the conditions are the best- warm, humid air from Mexico mixes with cold, dry air from Canada.
- 31. • Tornadoes occur most frequently in the US • Damage comes from strong winds & flying debris.
- 32. • Tornadoes are ranked on the Fujita Scale (by the amount of damage they cause.) • F0 light damage to F5 extreme damage. • F4 F5 tornadoes account for only 1% of all tornadoes.
- 33. • A tropical cyclone that has winds of 119kmh or higher. • Forms in the Atlantic, Pacific, & Indian Oceans. In western Pacific- typhoons.
- 34. HURRICANE FORMATION • It begins over warm ocean water as a low-pressure area (tropical disturbance). • It grows from a disturbance to a tropical storm and maybe to a hurricane.
- 35. • It draws energy from warm, humid air at ocean’s surface. • Warm air rises to form clouds, more air is drawn into the system. • Storms bands, high winds, & heavy rains spiral around a center.
- 36. • Cool, dry air sinks into the center (eye) of the hurricane. • Hurricanes last longer than other storms- usually a week or longer.
- 38. • Year round, most precipitation begins in the clouds as snow.
- 39. • Cold, dry air moves across warmer water picking up water vapor & heat from the water. Once the air reaches the other side of the lake, air condenses & falls as snow.
- 40. • In New York, Buffalo & Rochester are 2 of the snowiest cities in the US because of Lake-Effect Snow.
- 41. Snowstorm Safety • Find shelter from the wind. • It can be dangerous because high winds/snow limit your vision so you can get lost easily & you can lose a lot of body heat out in the cold.
- 43. Meteorologists • Scientists who study the causes of weather & try to predict it. • Meteorologists use maps, charts, & computers to analyze weather & prepare weather forecasts.
- 44. • Lines joining places that have the same temps.
- 45. • Lines joining areas with the same air pressure.
- 46. TECHNOLOGY • Has improved the accuracy of weather forecasts. • Weather balloons carry instruments into the troposphere & stratosphere to measure temp., air pressure, & humidity.
- 47. • Weather Satellites- orbit earth in the thermosphere, cameras make images of the earth’s surface, clouds, & storms which get sent to meteorologists to analyze.
- 48. • Computer Forecasts- gathers weather data from a large area then the computer works through thousands of calculations using equations from weather models to make forecasts for 12, 24, & 36 hours. Each one builds on the previous forecasts.