Graphing the Atmosphere Average Temperatures in Earth’s Atmosphere Average Temp. (°C) Altitude (km) MATERIALS  STEP 5: Label the five layers of the Reading handout, graph paper, pencil, colored pencils, 15 0 atmosphere. Write the entire word to ruler -18 5 label each layer.

-49 10  PROCEDURE -56 12   STEP 1: Assemble your graph and glue into your  notebook. -56 20  A. Cut off the extra paper on the top half of the second -51 25  page of the graph. Glue the two pieces of paper -46 30

together so the gridlines match. There will be a little -37 35 bit of overlap between 300 and 310.  STEP 6: Draw the four boundaries -22 40 B. The graph will be longer than the notebook and can between layers of the atmosphere. be folded up to fit. Fold the graph “in” at 390 and -8 45  Draw a horizontal line across the fold “back” at 180. -2 48 graph at each of the following altitudes: C. Cut off the extra paper on the right side so the graph -2 52 will fit in your notebook. Glue the back of the top  15 km -7 55 page into your notebook.  50 km -17 60  90 km  STEP 2: Read the background information about the -33 65  500 km atmosphere. Underline or highlight key words for easy -54 70 reference later on. -65 75  STEP 7: Find the location of the ozone

-79 80 layer.  STEP 3: Label the vertical and horizontal axes on the  Shade the location of the -86 84 graph. One should be labeled Average Temperature (°C) across the graph -86 92 and the other should be labeled Altitude (km). Use the  Label the ozone layer. data to help you figure out which one is which. -81 95 -72 100  STEP 4: The data table contains the average  STEP 8: Use your graph and the temperature reading at different altitudes in the Earth’s -60 200 background information to complete the atmosphere. Plot this data on the graph and connect -48 300 “Atmosphere Graph Reflection” questions. each of the points as you plot them. Use a ruler to draw -38 400 lines. Be careful to plot the negative temperatures correctly. -30 500 -72 600 THE ATMOSPHERE The atmosphere can be divided into five layers based on temperature differences. The layer closest to Earth is called the troposphere. Above this layer is the stratosphere, followed by the mesosphere, then the thermosphere, and finally the exosphere. The temperature differences in the layers are caused by the way solar energy is absorbed as it moves down through the atmosphere. Troposphere The Earth’s surface absorbs most of the solar energy. Some of the energy radiates off the surface as heat, which warms the troposphere. The average temperature of the troposphere decreases as the altitude increases. In other words, the higher up the air is, the colder it gets. The global average temperature on the troposphere rapidly decreases with altitude until the , which is the boundary between the troposphere and the stratosphere. Stratosphere The temperature begins to increase with altitude in the stratosphere. This warming is caused by ozone (O3), a form of oxygen which absorbs ultraviolet (UV) radiation from the sun. Ozone is a dangerous pollutant when it is found in the troposphere, but the ozone layer in the stratosphere, located approximately 20 to 30 kilometers above the surface of the Earth, protects us from the suns UV Glue this side down radiation. UV rays can cause sunburn, cancer, and genetic mutation. At the , the boundary between the stratosphere and the mesosphere, the temperature stops increasing with altitude. Mesosphere Weather balloons can only travel into the stratosphere below, and satellites orbit in the thermosphere above, so scientists have not been able to gather much information about the mesosphere. We do know that the air in the mesosphere is very thin so it does not absorb radiated heat from the sun, which makes the temperature decrease with altitude. It continues to decrease until the , which is the upper boundary of the mesosphere. Thermosphere and Exosphere At the mesopause, the temperature begins to increase again and this continues through the thermosphere, the warmest layer of the atmosphere. This layer is where solar radiation first hits the atmosphere and heats it. The air in the thermosphere is so thin, a thermometer cannot measure the temperature accurately and special instruments are needed. Even though it is very hot in the thermosphere, the molecules are so spread out, that it does not feel warm, so the International Space Station and other satellites can orbit safely through this layer of the atmosphere. The upper boundary of the thermosphere is the , after which comes the final layer of the atmosphere, the exosphere, which is where space begins.