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 air moves in over a cold air mass
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?
Students write 5 safety rules down for each 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 % 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