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Layers of the AtmosphereBy Jack Fearing, Lincoln Junior High School, Hibbing, Minnesota

OBJECTM: To discover how the atmosphere can be divided into layers based ontemperature changes at different heights, by making a graph.

BACKGROUND:The atn-rosphere can be divided into four layers based on temperature variations. Thelayer closest to the Earth is called the troposphere. Above this layer is the stratosphere,followed by the mesosphere, then the thermosphere. The upper boundaries between theselayers are known as the tropopause, the stratopause, and the mesopause, respectively.

Temperature variations in the four layers are due to the way solar energy is absorbed as itmoves downward through the atmosphere. The Earth's surface is the primary absorber ofsolar energy. Some of this energy is reradiated by the Earth as heat, which warms theoverlying troposphere. The global average temperature in the troposphere rapidlydecreases with altitude until the tropopause, the boundary between the troposphere andthe stratosphere.

The temperature begins to increase with altitude in the stratosphere. This warming iscaused by a form of oxygen called ozone (O3) absorbing ultraviolet radiation from thesun- Ozone protects us from most of the sun's ultraviolet radiation, which can causecancer, genetic mutations, and sunburn. Scientbts are concerned that human activity iscontributing to a decrease in stratospheric ozone. Nitric oxide, which is the exhaust ofhigtr- flying jets, and chlorofluorocarbons (CFCs), which are used as refrigerants, maycontribute to ozone depletion.

At the statopause, the temperature stops increasing with altitude. The overlyingmesosphere does not absorb solar radiation, so the temperature decreases with altitude.At the mesopause, the temperature begins to increase with altitude, and this trendcontinues in the thermosphere. Here solar radiation first hits the Earth's atmosphere andheats it. Because the atmosphere is so thin, a thermometer cannot measure thetemperature accurately and special instruments are needed.

DIRECTIONS:1. Table I contains the average temperature readings at various altitudes in the Earth,satmosphere- Plot this data on the graph on the worksheet, and connect adjacent pointswith a smooth curve. Be careful to plot the negative temperature numbers correitly.This profile provides a general picture of temperature at any given time and place;however' the actual temperature may deviate from the ur"*g" values, particularly in theIower atrnosphere.

Altitude (km) Temp (oC) Altitude (km) Temp fC)0 15 52 .|

5 I8 55 -7l0 -49 60 t7l2 -56 65 -JJ20 -56 70 -5425 -51 75 -6530 -46 80 -7935 -37 84 -864A 't1 92 -8645 -8 95 -8148 ^|-L 100 -12

TABLE 1Average Temperature Readings at Various Altitudes

2. Label the different layers of the atmosphere and the separating boundaries betweeneach layer.

3. Mark the general location of the ozone layer. You should place eight words on yourgraph in the correct locations: troposphere, tropopause, stratosphere, stratopause,mesosphere, mesopause, thermosphere and ozore layer.

QUESTIONS:l. What is the basis for dividing the atmosphere into four layers?

2. Does the temperature increase or decrease with altitude in the:

troposphere?

mesosphere?

stratosphere?

thermosphere?

3- What is the approximate height and temperature of the:

tropopause:

stratopause:

mesopause:

4. What causes the temperature to increase with height through the stratosphere, anddecrease with height through the mesosphere?

5. what causes the temperature to decrease with height in the troposphere?

Graph of Temperature at Various Altitudes

ALTITUDE (km above sea level * Y-axis)100

0

95

90

85

80

70

65

60

55

50

45

40

35

30

25

20

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