Chapter 9: Weather Patterns and Climate

1. Chapter 9: Weather Patterns and Climate

2. Aim: How do air masses affect weather?

3. Air Masses • An air mass is a large region of the atmosphere where the air has similar properties throughout • Gets its properties from the region it is from • Are named for the region they come from • When an air mass moves it brings the conditions with them

4. 4 types: • Continental polar: cold, dry air • Maritime polar: cool, moist air • Continental tropical: hot, dry air • Maritime tropical: warm, moist air • When 2 air masses meet, they form a boundary called a front • Weather changes rapidly at fronts because you are passing from one kind of air mass into another

5. Aim: How do fronts affect weather?

6. Types of Fronts • 4 types: • Cold Front • Cold air moves in under a warm air mass • Brings brief, heavy storms • Can cause strong winds and thunderstorms • After the storm, the weather is cooler and drier

7. Warm Front • Warm air moves in over a cold air mass • It brings light, steady rain or snow • Precipitation can last for days • Can bring fog • After the rain, the weather is warmer and more humid • Occluded Front • Occurs when a cold front and warm front meet • 2 ways this can happen

8. Cold front occlusion • Air behind the front is cold • Air ahead of the warm front is cool • Cold air is moving in on cool air and the warm is pushed up in between them • Weather is like that of a cold front • Warm front occlusion • Air behind front is cool not cold • Air ahead of warm front is cold • Weather is like that of a warm front

9. Stationary Front • Stays over an area for days without moving • Have calm weather

10. Aim: How do thunderstorms form?

11. Stages of Thunderstorms • Most common kind of severe storm • Form in cumulonimbus clouds called thunderheads • Usually have heavy rains, strong winds, thunder and lightning • Some can even produce hail • There are 3 stages during a thunderstorm

12. First Stage • Intense heat causes air to rise very quickly • Updrafts form and the cloud grows bigger and bigger • Water droplets and ice crystals grow larger too • Second Stage • When the rain starts falling air moves downward • Static electricity forms from the rubbing of upward air and downward air

13. Lightning occurs when static electricity builds up • Lightning is unpredictable • Third Stage • The storm dies when the downdraft becomes stronger than the updraft • Heavy rains subside and finally stop • Thunderstorms usually form in the warm air just ahead of a cold front

14. Aim: How do tornadoes happen?

15. Tornadoes • A tornado is a violent whirling wind that moves across the ground in a narrow path • Form when dry, cold air masses mix with warm, moist air masses. • When the updraft is really strong air rushes in from all sides causing the air to curve into a spin • This spin lowers the air pressure even more, causing air to rush in even faster

16. As the tornado gets stronger a funnel forms that touches the ground • Winds can reach up to 300 mph in the center of a tornado • The direction of a tornado can continually change • Most tornadoes occur in the Midwest of the United States • They mostly likely occur where there are big differences in the air masses

17. Aim: How do hurricanes form?

18. Hurricanes • Are very large, swirling storms with very low pressure at their center • They form over tropical oceans • Strong heating and lots of evaporation cause a large low pressure center to form • The Coriolis effect causes winds to spiral counterclockwise and clusters of thunderstorms are pulled into the spiral • The thunderstorms merge forming the storm

19. The lower the pressure, the stronger the winds blow • In order for the storm to be considered a hurricane, the winds need to reach 75 mph or higher • Hurricanes have an eye at the center of the storm • The eye is an area of light winds and clear skies • Hurricanes can grow 400 miles in diameter

20. Aim: How do hurricanes affect ocean waves?

21. Hurricane winds cause large waves in the ocean • These waves pound the shore for days before the hurricane hits • The storm surge causes the most damage • Storm surges are caused by low air pressure • It causes the sea to rise, along with heavy rain from the hurricane

22. Storm surges cause flooding, which destroys homes and wears away beaches • Hurricanes begin to die when they move onto land because it has no water to replace what falls as rain

23. Aim: How can you be safe in a storm?

24. Aim: How can radar track storms?

25. Radar • Doppler radar is used to find storms as they form • Radar stands for radio detection and ranging • Radar sends out radio waves and records their echoes • The change in echoes gives scientists clues • It is used to track storms because radio waves reflect off storm clouds

26. With the radar, scientists can tell if rain is moving toward or away from an area, and spot spinning motions of clouds • Spotting motions of clouds can help warn scientists of tornadoes or hurricanes • Doppler radar helps scientists find and track thunderstorms, tornadoes and hurricanes

27. Aim: What is climate?

28. Climate • Is the average weather pattern of a region • Climate can be described by the following factors: temperature, precipitation, winds, distance from coast, mountain ranges and ocean currents • We can also describe climate by the plants that live their b/c plants require their own conditions for growth, such as amount of sunlight, precipitation and temperature

29. Examples: • Alaska has a climate of long, cold winters and short cool summers • Florida has a climate of long, hot summers and short, cool winters

30. Aim: What affects climate?

31. Factors that Affect Climate • Latitude • is the measure of how far north or south a place is from the equator • Temperatures are different at different latitudes due to the angle of insolation • 3 different zones: • Tropical Zone • Temperate Zone • Polar Zone

32. Bodies of Water • Most of Earth is covered with water • Land and water cool and heat at different rates • Land heats up faster in sunlight and cools off faster • Air temperatures over land are warmer in the summer and cooler in the winter than over oceans at the same latitude

33. Winds and Ocean Currents • The westerlies blow in the middle latitudes • They bring warm, moist air to the west coast and push air masses and fronts • Ocean Currents are also moved by winds • Gulf stream is a warm current that flows up the east coast • California current is a cool current that moves down along the west coast

34. Altitude • Is the measure of how high a place is above sea level • The higher a place the cooler it is

35. Aim: How does the Greenhouse Effect affect Earth?

36. Earth’s Energy • Earth absorbs heat from the sun • It also gives off heat into space • Radiative balance is when the amount of energy gained equals the energy lost • Average temperature of Earth = 59˚F • The atmosphere protects Earth from getting too hot or too cold • Only about ½ of incoming sunlight reaches Earth

37. 30% reflects off of particles and clouds back to space • The atmosphere absorbs 15- 20% of the heat • This keeps temperatures from rising too high • At night clouds aid in keeping the night from getting too cold

38. The Greenhouse Effect • The atmosphere keeps Earth warmer than it would be • Earth’s atmosphere acts like the glass in a greenhouse by letting in sunlight, but not letting heat escape • 2 main greenhouse gases are water vapor and CO2 • Methane, nitrous oxide and chlorofluorocarbons (CFC’s) have a small effect

39. These greenhouse gases are increasing due to human activity • With this increase Earth’s climate can change and make our planet warmer • The increase in these gases have a great effect on our environment

40. Aim: What causes climate change?

41. Causes of Climate Change • Over time Earth has undergone changes, which caused periods of cooling and heating • Shifts in the radiative balance is caused by changes in sunlight, currents and landmasses and volcanoes • Sunlight • the amount of energy the sun sends out changes • These changes are due to sunspots

42. Sunspots are dark areas that appear on the surface of the sun • These spots are cooler than other parts of the sun • They are not permanent • Sunspot maximum-large count of sunspots, which happens about every 11 years • Around the time of a sunspot maximum, earth’s temperature goes up

43. Ocean Currents • They move heat from the equator to the poles • Change in speed and direction of currents can explain sudden and long term climate changes • Landmasses • Continents have changed positions and continue to move • climate will change with their locations

44. Volcanoes • Eruption of volcanoes send dust and gases into the atmosphere • The dust and gases could block out the sun and cause cooling • In the past volcanic eruptions were very common and could have caused the ice ages • They are less common today, but still cause cooling, just not long term changes