1. Atmosphere
6th Grade Science

2. Earth's Atmosphere Thin Gaseous envelope
Figure 1.2
The atmosphere is a thin layer of air that protects the Earth’s surface from extreme temperatures and harmful sun rays

3. Composition of Atmosphere (Mixture of gases, solids, and liquids)
Early atmosphere was much different than today
Volcanoes produced nitrogen and carbon dioxide, but little oxygen
More than 2 billion years ago, early organisms began producing oxygen
Eventually, oxygen formed an ozone layer that protected Earth from harmful rays
Green plants and diverse life forms developed

4. Atmospheric Gases (Mixture of gases, solids, and liquids)
Nitrogen %
Oxygen %
Water Vapor – 0 to 4%
Used for clouds and precipitation
Carbon Dioxide %
Keeps Earth warm and is used by plants to make food
Argon - .93%
Traces of neon, helium, methane, krypton, xenon, hydrogen, and ozone

5. Atmospheric Gases (Mixture of gases, solids, and liquids)
Atmosphere is changing with the introduction of pollutants; increasing human energy use is increasing the amount of carbon dioxide
Pollutants mix with oxygen and other chemicals to form smog
Aerosols include solids such as dust, salt, and pollen
Liquids include water droplets and droplets from volcanoes

6. Five Layers of the Atmosphere

7. Lower Layers of Atmosphere
Troposphere: lowest layer – extends up to 10km; contains 99% of the water vapor and 75% of the atmospheric gases
The troposphere is the first layer above the surface and contains most clouds and half of the Earth's atmosphere.
Weather occurs in this layer.
Most of the layer’s heat is from Earth
Temperature cools about 6.5 degrees Celsius per kilometer of altitude.

8. Lower Layers of Atmosphere
Stratosphere – directly above troposphere, extending from 10 km to about 50 km above Earth’s surface
Portion of the upper layer contains high levels of a gas called ozone
Many jet aircrafts fly in the stratosphere because it is very stable. Also, the ozone layer absorbs harmful rays from the Sun.

9. Upper Layers of Atmosphere
Mesosphere – extends from the top of the stratosphere to about 85 km above Earth
Coldest layer
Meso- means middle
Meteors or rock fragments burn up in the mesosphere.

10. Upper Layers of Atmosphere
Thermosphere – thickest atmospheric layer found between 85 km and 500 km above Earth’s surface
The thermosphere is a layer with auroras, known for its high temperatures.
Warms as it filters out X-rays and gamma rays from the Sun
Contains the ionosphere and exosphere

11. Upper Layers of Atmosphere
Ionosphere here, too – help carry radio waves.
Exosphere - The atmosphere merges into space in the extremely thin exosphere. This is the upper limit of our atmosphere.
Outer layer where space shuttle and satellites orbits.

12. Atmospheric Pressure
Molecules closer to the surface are more densely packed (at higher pressure) together than those higher in the atmosphere because of the mass of gases pressing down on them from higher in the atmosphere

13. Temperature in atmospheric layers
The troposphere is warmed primarily by the Earth’s surface; temperature decreases as altitude increases in this layer.
Temperatures increase as altitude increases in the stratosphere, particularly in the upper portion – ozone
Temperatures decrease with altitude in the mesosphere
Thermosphere and exosphere are the first to receive Sun’s rays, so they are very hot

14. The Ozone Layer
About 19 km to 48 km above Earth in the stratosphere (90%) and troposphere (10%).
Layer of 3-atom molecules that protects the Earth from the Sun’s harmful ultraviolet radiation
Life depends on the ozone!
Pollutants called chlorofluorocarbons (CFCs) are destroying the ozone
CFCs are used in refrigerators, air conditioners, aerosol sprays, and foam packaging ~ if products leak, CFCs enter atmosphere
Ozone layers has a large hole over Antarctica and a smaller one over the North Pole

15. Solar energy
Some of the Sun’s energy coming through Earth’s atmosphere is reflected or absorbed by gases and/or clouds in the atmosphere.

16. Solar energy Greenhouse Effect
Solar energy that is absorbed by the Earth’s land and water is changed to heat that moves/radiates back into the atmosphere (troposphere) where gases absorb the heat, a process known as the greenhouse effect.

17. Greenhouse Animation

18. Heat
Energy that flows from an object with a higher temperature to an object with a lower temperature
Heat is transferred through the atmosphere by:
Radiation:energy that is transferred in the form of rays or waves
Conduction:energy that is transferred when molecules bump into each other
Convection:energy that is transferred by flow of material
Molecules move closer together, making air more dense, and air pressure increases
Cold air sinks, pushing up warm air, which then cools and sinks, pushing up more warm air

19. What is Weather? State of the atmosphere at a specific time and place
Includes such conditions as air pressure, wind, temperature, and moisture in the air
Temperature is a measure of air molecule movement
Sun’s energy causes air molecules to move rapidly; temperatures are high and it feels warm
When less of the Sun’s energy reaches air molecules, they move less rapidly and it feels cold

20. What is Weather?
Energy is transferred between fast-moving molecules and slower-moving molecules
CONDUCTION – transfer of energy when molecules collide
CONVECTION – occurs when warm air rises and cool air sinks; it’s the transfer of heat, usually in liquids or gases

21. You might pick heat or sun….but another good choice would be
If we were to pick one term to help explain why we have weather, what do you think would be a good word?
You might pick heat or sun….but another good choice would be
Convection

22. After the atmosphere is warmed by radiation and conduction, the heat is transferred throughout the atmosphere by convection.
Since warmed air has more space between the molecules, it’s less dense and rises
Cooled air is more dense and tends to sink
In general, air near the equator tends to rise and air near the poles tends to sink

23. Take a look at this!

24. Notice the band of clouds around the equator ?
This is the ITCZ or inter tropical convergence zone

25. Why do you think there is this band of clouds near the equator?

26. Did you figure it out? Warm, moist air in the tropics rises
Cold air can hold less moisture than warm air
As the moist air rises, it condenses and forms clouds!

27. Now What?
Ok, so we know that the weather moves around on these highways and that warm air rises and cold air sinks.
But why is it sunny one day, and rainy the next?

28. Let’s take another look at the weather map
Notice that there are H’s and L’s on the map
There are also blue lines with spikes and red lines with half circles
Let’s take a closer look!

29. AIR PRESSURE Air weight that varies over Earth’s surface
Warmer air is less dense and exerts less pressure
Cooler air is more dense and exerts more pressure

30. High Pressure Areas
When cooler air sinks and is warmed, the air can hold more moisture
This usually means sunny skies
Winds tend to move clockwise around a high

31. Low Pressure Areas
When warm air rises and is cooled, the air can not hold as much moisture
Often, these areas are associated with precipitation and stormy weather
Winds tend to move counter clockwise around the low

32. So, if you see a big H on the weather map over the area you live, you can expect fair weather

33. When you see a big L in your area, there will probably be stormy weather

34. These highs and lows move or less along the jet stream and bring us our weather changes

35. Humidity The amount of water vapor in the air
Temperature affects how much moisture is in the air - warmer air can hold more water vapor, tending to make it more humid
Relative humidity – the amount of water vapor in the air compared to what it can hold at a specific temperature
When air cools, it can’t hold as much water vapor, so the water vapor condenses to liquid or forms ice crystals
Dew point – the temperature at which air is saturated and condensation forms

36. Clouds
Form when air rises, cools to its dew point, and becomes saturated
Shape and height of clouds vary with temperature, pressure, and water vapor in atmosphere

37. Clouds Shape Stratus-smooth, even sheets or layers at low altitudes
Cumulus-puffy, white clouds, often with flat bases
Cirrus-high, thin, white feathery clouds made of ice crystals
Height
Cirro – high clouds
Alto – middle-elevation clouds
Strato – low clouds
Nimbus clouds are dark and so full of water that sunlight can’t penetrate them

38. Clouds LOW CLOUDS – form at 2,000 m or less in altitude
Cumulus – puffy clouds formed when air currents rise and carry moisture
Stratus – layered dull, gray sheets that can cover the entire sky
Nimbostratus – low, dark, thick layers that hide the Sun

39. Clouds Cumulus · Clouds formed at medium or low elevation.
· Cumulus clouds are puffy with flat bottoms.
· When cumulus clouds are white they often signal fair weather, but when they are darker, they may signal rain or thunderstorms.

40. Clouds
Stratus
Clouds formed at medium or low elevation; spread out layer upon layer covering a large area
As stratus clouds thicken, precipitation usually occurs over that area.

41. Cumulus

42. Stratus

43. Nimbo-stratus clouds

44. Clouds MIDDLE CLOUDS – form between 2,000 m and 8,000 m in altitude
Most are layered
Names have alto- prefix (altocumulus and altostratus)
Can produce light precipitation

45. Alto-cumulus clouds

46. Alto-stratus Clouds

47. Clouds HIGH AND VERTICAL CLOUDS Cirrus – wispy, high-level clouds
Cirrostratus – high, layered clouds that can cover the sky
Cumulonimbus – known as thunderstorm clouds; produce heavy precipitation

48. Clouds
Cirrus
Clouds formed at high elevations; wispy clouds usually consisting of ice crystals that signal fair weather or may also signal an approaching warm front.

49. Cirrus

50. Cumulo-nimbus
Clouds
aka:
Thunderheads

51. Cirro-cumulus clouds

54. Fog

55. Fog

56. Cloud Cover Symbols
You will often see the circles drawn on a weather map

57. Air Movement
Wind: Movement of air from one temperature or pressure area to another
Different areas of Earth receive different amounts of the Sun’s energy
Equator’s warm air, being less dense, is pushed upward by denser, colder air
Poles’ cold air, being more dense, sinks and moves along Earth’s surface
CORIOLIS EFFECT: spinning of the Earth causes moving air to turn to the right in the northern hemisphere and to the left in the southern hemisphere

58. Global Winds
Wind patterns, caused by convection currents combined with the Coriolis effect, of Earth that affect the world’s weather
Near equator, very little wind and daily rain patterns called the doldrums
Surface winds:
Between equator and 30 degrees N and S latitude are steady trade winds
Between 30 and 60 degrees N and S latitude, the westerlies blow in opposite direction from the trade winds.
The polar easterlies blow from northeast to southwest near the north pole and from southeast to northwest near the south pole

59. Global Winds
TRADEWINDS
Equatorial doldrums
TRADEWINDS

60. The Weather Highways
The rotation of the earth creates the Coriolis effect.
The Coriolis effect causes the air and water to be deflected to the right north of the equator.
This creates global weather highways

61. The Westerlies
Because of our latitude, most of our weather comes from the west
Looking at the weather map, what type of weather might we expect?
What type of weather might we expect in a few days?

62. Let’s break for a short review
1.Transfer of heat in liquids or gases_____
2. _____ air is dense and tends to sink.
3. Band of clouds found around the equator______
4. Cold air holds _____ moisture than warm air
5. The Coriolis effect causes the air and water to be deflected to the _____ of the equator

63. How did you do?
1. CONVECTION
2. COLD
3. ITCZ
4. LESS
5. RIGHT

64. Fronts and Air Masses
Because air and moisture move in the atmosphere, weather is constantly changing
Air pressure – measured by barometer
An air mass is a large body of air whose temperature and moisture are fairly similar at a given altitude; properties like the part of Earth’s surface over which it formed
Fronts are boundaries separating different air masses – clouds, precipitation, and storms occur at frontal boundaries
There are four different air masses that affect the United States

65. The Air Masses cP( continental polar) : cold, dry stable
cT( continental tropical) : hot, dry, stable air aloft, unstable at the surface
mP( maritime polar) : cool, moist, unstable
mT( maritime tropical) : warm, moist, unstable

66. This map shows the air mass source regions and there paths

67. Warm Fronts A warm front is warm air displacing cool air
Shallow leading edge warm air must “overrun” cold air
These are usually slow moving
Widespread precipitation develops!

68. Warm Front
2. Warm Front: The zone where warm air is replacing colder air
In U.S., warm fronts usually move from southwest to northeast
Air gets more humid after a warm front moves through

69. Cold Fronts Cold air advances into region of warm air
Intensity of precipitation greater, but short lived
Clearing conditions after front passes
Usually approaches from W or NW
Temperature drops; narrow band of violent storms!

70. Cold Front
1. Cold Front: The zone where cold air is replacing warmer air
In U.S., cold fronts usually move from northwest to southeast
Air gets drier after a cold front moves through

71. Stationary Fronts Surface positions of the front do not move
Often a region of clouds and precipitation

72. Stationary Front
3. Stationary Front: When either a cold or warm front stops moving
When the front starts moving again it returns to either being a cold or warm front

73. Occluded Fronts Cold front overtakes warm front
Involves three air masses of different temperatures
Often found
close to the low pressure center
Cloudy weather with precipitation!

74. Occluded Front
4. Occluded Front: Formed when a cold front overtakes a warm front
This occurrence usually results in storms over an area
In U.S., the colder air usually lies to the west
MENU

75. Ready for a little quiz?
Here we go!

76. 1.
Winds in a low pressure system move _____ around the low

77. 2.
What type of front can be found close to point D ?

78. 3.
Which of these fronts would you expect to have greater precipitation, but be short lived as the front passes?

79. 4.
Give the name of the air mass that would have the following characteristics:
cool, moist, unstable

80. 5. That important weather word that refers to the transfer of heat

81. 6. In general, air near the equator tend to_____ ( rise or fall )

82. 7.
It causes air and water to be deflected to the right north of the equator

83. 8. Which of the weather highways usually controls our weather

84. Warm air holds ( more or less ) moisture than cold air9.
Warm air holds ( more or less ) moisture than cold air

85. 10.
If there is a big H on the weather map where you live, would you expect fair or stormy weather

86. Let’s check the answers!
How did you do?
Let’s check the answers!

87. Answers 1. Counterclockwise 8. Westerlies 2. Cold 9. More
3. Cold Fair
4. Maritime polar (mP)
5. Convection
6. Rise
7. Coriolis

88. Weather Tools Anemometer- A tool used to measure
wind speed in miles per hour.
Wind vane
· A tool used to measure wind direction.
· Sometimes referred to as a
wind-weather vane or a wind sock.
· Wind direction is described by the direction from which the wind is blowing.
Thermometer - A tool used to measure air temperature in degrees Fahrenheit or Celsius.

89. Weather Instruments Video 1 15:01 Weather Instruments Video 2 19:41
Weather Tools
Sling Psychrometer-
A two-thermometer instrument also referred to as a wet-dry bulb used to measure relative humidity (the amount of water vapor in the air).
Temperatures readings are converted using a relative humidity table.
Weather Instruments Video 1 15:01
Weather Instruments Video 2 19:41

90. Weather Tools
Barometer- A tool used to measure air pressure in inches of mercury or millibars (mb).
Rain gauge- A tool used for measuring the amount of precipitation in inches or centimeters.

91. Weather Map Symbols

92. MENU

93. Reading a weather map
ISOBAR= connects areas of equal pressure BAR comes from BARometric pressure

94. Reading a weather map...
Isotherm: Connects areas of equal temperature; therm means temperature

95. Station Model

96. Station Models
Information found on a station model can include cloud cover, temperature (85°F), wind direction and speed, precipitation (snow, rain), or barometric pressure (1002 mb).
Station models from specific locations provide information that can also be used to predict weather patterns.

97. Weather Station (not on the TV) Weather conditions at specific location
Current Conditions!!

98. Satellites & Radar Satellites
· Satellite images are used for seeing cloud patterns and movements.
· For example, hurricane clouds and movement can be observed using satellite images.
Radar
· Radar images can be used to detect cloud cover, rainfall or storm location, intensity, and movement, as well as the potential for severe weather (for example, hurricanes or tornadoes).

99. Severe Weather
Thunderstorms occur inside warm, moist air masses and at fronts
Warm, moist air is forced rapidly upward, where it cools and condenses
Strong updrafts of warm air and sinking, rain-cooled air cause strong winds

100. Lightning
Movement of air inside a storm cloud causes parts of the cloud to become oppositely charged
Current flows between the regions of opposite electrical charge, forming a lightning bolt
Thunder – lightning superheats the air, causing it to expand rapidly and then contract, forming sound waves

101. Tornado
Violent, whirling wind that moves in a narrow path over land

102. Hurricane
Large, swirling, low-pressure system that forms over tropical oceans
Heat energy from moist air is converted to wind that can reach speeds of 250 km/h

103. Blizzard
A winter storm with strong winds, cold temperatures, and low visibility, that lasts more than three hours 

104. Severe Weather Safety
A National Weather Service WATCH means conditions are favorable for severe weather to develop
A warning means that severe weather conditions already exist
Meteorologists study and predict weather
National Weather Service makes weather maps and issues watches and warnings