2. Important Vocabulary
Weather – the condition of Earth’s atmosphere at a particular time and place. Atmosphere – the envelope of gases that surrounds the planet

3. The Main gases in the Earth’s Atmosphere
~ 75% Nitrogen
21% Oxygen
Less than 1% Carbon Dioxide
Argon makes up most of the other 1%

5. Atmosphere
The atmosphere is a system that interacts with other Earth systems.
Events in one part of the atmosphere affect other parts of the atmosphere.

6. Air Pressure
Because air has mass, it also has other properties, including density and pressure.
Density – the amount of mass in a given volume of air
D = M/V
Air Pressure – the result of the weight of a column of pushing on an area
P = F/A

7. Instruments to measure air pressure
Barometers
Mercury barometer
Consists of a long glass tube that is closed at one end and open at another
Aneroid barometer
Aneroid means “without liquid”
Has an air tight chamber
Chamber is connected to a dial by a series of springs and levers.
When pressure increases, the thin walls of the chamber are pushed in. When the pressure drops, the walls bulge out.

9. Units of air pressure
Most weather reports for the public use inches of mercury. (Ex. The air pressure is 30 inches)
The National Weather Service maps indicate air pressure in millibars.

10. The pressure of the atmosphere is equal to 1 bar (1000 millibars).
1 inch of mercury =
33.86 millibars
30 inches of mercury =
~ 1,016 millibars

11. Standard air pressure at sea level is 29. 92 inches of mercury
Standard air pressure at sea level is inches of mercury. A mercury reading higher than inches, with rising or steady pressure generally indicates fair weather, becoming cloudy and warmer with rapidly falling pressure. A mercury reading from inches to inches with rapidly falling pressure means precipitation is coming. A mercury reading under inches with rising or steady pressure means it will start to clear and become cooler, with slowly falling pressure it is an indication of precipitation, and rapidly falling pressure would indicate a storm.

12. Plickers ?
This barometer uses air tight chamber WITHOUT liquid to measure air pressure. A.) Mercury Barometer B.) Annathermometer C.) Aneroid Barometer D.) All barometers

13. Plickers ?
Most of the atmosphere is made up of ____. A.) Oxygen B.) Carbon Dioxide C.) Argon D.) Nitrogen

14. Altitude A.K.A elevation, which is the distance above sea level
Sea level – average level of the oceans.
Indiana is about 700 feet above sea level.
Air pressure decreases as altitude increases.
Analogy - Stack of books
As air pressure decreases, so does density.

15. Altitude continued…
As you go up through the atmosphere, the density of the air decreases.
Density = mass / volume
Air contains 21% oxygen, whether you are at sea level or on top of a mountain, but since there is more space(volume) at the top of a mountain, the density decreases.
Therefore, the air you breathe at the top of a mountain has fewer oxygen molecules per cubic meter than at sea level

17. Plickers ?
Where is the atmospheric pressure the greatest? A.) closest to earth B.) in the middle of the atmosphere C.) at a high altitude D.) closest to space

18. Layers of the atmosphere
Scientists have divided Earth’s atmosphere in to main layers, which are classified by changes in temperature.
Troposphere
Stratosphere
Mesosphere
Thermosphere

19. Question Where is most of the gas in the atmosphere found?
Close to Earth’s surface

20. Troposphere Where we live Inner, or lowest layer of Earth’s atmosphere
Tropo – means turning or changing
Weather takes place in this layer
Average thickness is ~ 12 km
Shallowest and most dense layer
Contains almost all the mass of the atmosphere
Altitude goes , temperature goes
Water at the top of this layer forms thin, feathery clouds of ice

21. Stratosphere Above troposphere 12km – 50 km above Earth’s surface
Strato – means layer or spread out
Contains ozone (O3)
The ozone layer filters out UV light and absorbs energy from the sun, which warms the air in this layer

22. Ozone over time

23. Mesosphere Meso – means middle 50 – 80 km above the Earth’s surface
Protects Earth’s surface from being hit by most meteroids

24. Thermosphere Outermost layer
80 km above Earth’s surface outward into space
No definite outer limit
2 layers aurora borealis
Ionosphere
exosphere

25. Plickers ?
What layer of the atmosphere do we live in? A.) Troposphere B.) Stratosphere C.) Mesosphere D.) Thermosphere

27. Plickers ?
Which layer means middle layer? A.) Troposphere B.) Stratosphere C.) Mesosphere D.) Thermosphere

28. Plickers ?
Which layer of the atmosphere does weather occur in? A.) Troposphere B.) Stratosphere C.) Mesosphere D.) Thermosphere

29. Energy in Earth’s Atmosphere
Electromagnetic waves – form of energy that can move through the vacuum of space
Most of the energy from the sun travels to Earth in the form of visible light and infrared radiation. A smaller amount arrives as ultraviolet radiation.

30. Visible Light Only part of the spectrum we can see ROY G BIV Red
Orange
Green
Blue
Indigo
Violet

31. Radiation – the direct transfer of energy by electromagnetic waves
Infrared radiation is not visible by humans, but can be felt as heat.
The sun gives off ultraviolet radiation.
Ultraviolet radiation can cause sunburns.

32. Some sunlight is absorbed or reflected by the atmosphere before it can reach the surface. The rest passes through the atmosphere to the surface.

33. Scattering – dispersing light in all direction

34. Why is the sky blue?
When you look at the sky, the light you see has been scattered by gas molecules in the atmosphere.
Gas molecules scatter short wavelengths of visible light (B + V) more than long wavelengths (R + O)
Scattered light looks bluer than ordinary sunlight.
That’s why the clear daytime sky looks blue.

35. Greenhouse effect
Earth’s surface radiates some energy back into the atmosphere as infrared radiation.
Much of the IR radiation doesn’t immediately travel all the way back into space.
Instead, it is absorbed and held by water vapor, CO2, methane, and other gases in the air.

36. The greenhouse effect is a natural process
The greenhouse effect is a natural process. It keeps Earth’s atmosphere at a comfortable temperature.
Over time, the amount of energy absorbed by the atmosphere and Earth’s surface is in balance with the amount of energy radiated into space.
In this way, Earth’s average temperatures remain fairly constant.

38. Winds Differences in air pressure cause the air to move.
Wind - the movement of air parallel to Earth’s surface.
Most differences in air pressure are caused by the unequal heating of the atmosphere.

39. Measuring wind Wind direction is determined by a weather vane.
Anemometer – measures wind speed
Windchill Factor – the increased cooling that a wind can cause
The temp outside is 20 °F, but with a wind speed of 30 mph, the windchill factor makes it feel like 1 °F

40. Local Winds
Winds that blow over short distances are called local winds.
Local winds are caused by the unequal heating of Earth’s surface within a small area.
These winds form only when large scale winds are weak.
2 types of local winds
Sea breezes
Land breezes

41. Local vs. Global
Like local winds, global winds are created by the unequal heating of the Earth’s surface.
Unlike local winds, global winds occur over a large area.

42. Global winds
Global winds and the jet stream have an effect on weather and climatic conditions on Earth.
Global winds are found in each convection region.
Because convection cells are in place in the atmosphere and Earth is spinning on its axis, these global winds appear to curve. This is known as the Coriolis effect.
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43. Global winds
In the global wind belt regions, the prevailing direction of the winds and how air movement in these large regions affects weather conditions.
The trade winds blow from east to west in the tropical region moving warm tropical air in that climate zone.

44. Doldrums – calm area where warm air rises
Horse latitudes – 2 calm areas of sinking air
Trade winds blow from the horse latitudes toward the equator
Prevailing westerlies blow from west to east
Polar easterlies blow cold air away from the poles

45. Global winds
The prevailing westerly winds blow from west to east in the temperate region.
The temperate zone temperatures are affected most by the changing seasons, but since the westerly wind belt is in that region, the weather systems during any season move from west to east. Since the United States is in the westerly wind belt, the weather systems move across the country from west to east.

46. Global Winds
Convection can cause global winds. These winds then move weather systems and surface ocean currents in particular directions.
Due to the spinning of Earth, the weather systems in these regions move in certain directions because the global wind belts are set up.

52. Invention of weather instruments
1500’s Galileo invented water thermometer
1643 Torricelli invented mercury barometer
1667 Hooke invented anemometer
1719 Fahrenheit developed temp scale based on boiling/freezing water
1735 Hadley explained how the earth’s rotation influences winds in tropics
1742 Celsius developed the centigrade temp scale

53. 1787 Charles discovered relationship between temp and a volume of air
1835 Coriolis used math to demonstrate the effect that the earth’s rotation has on atmos. Motions
1869 first isobars were placed on map
1920 concepts of air masses and weather fronts were formulated in Norway
1940’s upper air ballons/3-D view of atmos
1950’s high speed computers
1960 Tiros 1 first weather satellite