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Even more practice questions

# Even more practice questions - Atmospheric Sciences 101...

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Atmospheric Sciences 101 Midterm Exam #1 solutions and discussion 1.a) Draw the vertical temperature structure of Earth's atmosphere on the figure below. b) Label the four main layers of the atmosphere and the boundaries between these layers (i.e. the "spheres" and the "pauses"). See the textbook for the drawing and the names. Aside from forgetting the names of some of the layers, the most common error was to place the tropopause too high (it is located between 8-20 kilometers, depending on location and season). The surface temperature should be reasonable. Note that the "exosphere" is located at several hundred kilometers altitude and should not appear on this figure. c) Is the temperature lapse rate positive or negative in the lowest layer? negative (temperature decreases with height in the troposphere) d) In what layer does "weather" mostly occur? troposphere e) In what layer is ozone concentration highest? stratosphere (ozone concentration is also fairly high in the mesosphere so we gave partial credit for that answer also) f) In what layer is the photodissociation of oxygen (O 2 ) molecules an important source of heat? thermosphere (this is why the temperature increases dramatically above 100 km). We also gave partial credit for mesosphere and stratosphere, since photodissociation of oxygen also occurs in these layers (although absorption of solar radiation by ozone is the main heat source). The exosphere is defined in terms of escape velocity and there is so little oxygen at an altitude of several hundred kilometers that photodissociation of oxygen is negligible. g) Is the air pressure greater at the surface or at 20 km? surface Briefly state why. Air pressure is the weight of the column of air above. At the surface, you have 20 kilometers more air above you than you have at 20 kilometers altitude, so the pressure is higher at the surface by the weight of this amount of air. Many people merely stated that "pressure decreases with height," or "density is lower at the surface and pressure is proportional to density," neither of which sufficiently explains WHY this is so. Incidentally, the fact that temperature decreases with height in the troposphere is NOT the reason that air density and pressure decrease in this layer; the pressure decreases with height in the stratosphere and the lapse rate in the stratosphere is positive! The earth's pressure profile would be virtually unchanged if the entire atmosphere were at uniform temperature. The main reason that pressure decreases rapidly with altitude is because air is compressible and as you go up you rapidly rise through much of the mass of the atmosphere so it no longer pushes down on you due to the force of gravity. 2. a) Name the two main gases in our atmosphere. Nitrogen and Oxygen b) Name the two main gases present in volcanic eruptions.

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