METR 104:
Our Dynamic Weather
(Lecture w/Lab)
Pre-class Quiz #4:
for on-Line Reading #4, Plus More
Dr. Dave Dempsey
Dept. of Geosciences
SFSU, Fall 2012

This is a "preview" version of Pre-class Quiz #4, which is based on On-line Reading Assignment #4 plus a related diagram attached to the quiz. The "preview" version is suitable for printing and leisurely inspection before you submit your answers to the the interactive or "live" version—that is, the real thing. When you feel ready to submit your answers, go to iLearn's METR 104 "Pre-class Quizzes" section, select the interactive version, and follow its instructions.

(Responses must be submitted by 1:05 p.m. Monday, Oct. 22. (If you leave the interactive version before submitting your answers, you can save answers already entered by clicking on the "Save without submitting" button at the bottom of the quiz page, and you can return later. In any case, be sure to submit your responses by the deadline by clicking on the "Submit all and finish" button at the bottom of the quiz page.)

Description: The five questions below (all are multiple choice) address points made about radiation in On-line Reading Assignment #4.

The Questions:


(1) Multiple Choice. Radiative Absorption by Greenhouse Gases. All greenhouse gases absorb certain wavelengths of radiation well (and hence are capable of emitting those wavelengths, too). What type of radiation do all greenhouse gases absorb well (and hence can also emit)? (Select the one best answer.)

  1. longwave infrared radiation (also known as terrestrial radiation)
  2. short wavelengths of infrared radiation
  3. visible light
  4. ultraviolet radiation

(2) Multiple Choice. Contributions to the Greenhouse Effect. Certain gases in the air ("greenhouse gases"), plus clouds, contribute to the greenhouse effect, which is responsible for keeping the earth's surface about 60°F warmer than what it would be otherwise. (Without the greenhouse effect, life as we know it would not exist--the earth would be too cold.)

Of the greenhouse gases, which two contribute the most to the greenhouse effect? (These are also the two most abundant of the greenhouse gases in the air.) (Select the one correct answer.)

  1. nitrogen is the biggest contributor, followed by oxygen
  2. nitrogen, followed by water vapor
  3. oxygen, followed by carbon dioxide
  4. water vapor, followed by carbon dioxide
  5. carbon dioxide, followed by ozone

(3) Multiple Choice. Cause of Global Warming. The global average temperature of the earth's surface and lower atmosphere has been increasing for most of the last 100 years. The evidence for this is diverse and compelling. There is also very strong evidence for the cause of that warming. Based on the current evidence, what is the likely cause? (Select the best answer.)

  1. The sun has increased its output of solar radiation.
  2. The earth entered one of its natural cycles of warming and we're still in it.
  3. Volcanic eruptions have become less frequent in the last century.
  4. Carbon dioxide concentrations have increased, strengthening the greenhouse effect.

(4) Multiple Choice: The Earth's Long-Term, Global Average Energy Budget. Refer to the accompanying diagram, which shows the earth's long-term, global average energy budget for the atmosphere and the surface. Each number on the diagram represents the rate (in Watts) at which energy arrives at, exits through, is reflected by, is absorbed by, or is emitted by a (horizontal) square meter. ("LWIR" = "longwave infrared radiation")

In the left half of the diagram, note that the average insolation (intensity of incoming solar radiation on a horizontal surface) at the top of the atmosphere is 342 Watts per square meter (W/m2).

Based on information in diagram, roughly what percentage of the solar radiation arriving from the sun is reflected back to space by the atmosphere and the earth's surface combined? (Select the one correct answer.)

The Earth's Long-Term, Global Average Energy Budget

  1. 107 W/m2 out of 342 W/m2 (31%) is reflected back to space.
  2. 168 W/m2 out of 342 W/m2 (49%) is reflected back to space.
  3. 67 W/m2 out of 342 W/m2 (20%) is reflected back to space.
  4. 390 W/m2 out of 342 W/m2 (114%) is reflected back to space.

(5) Multiple Choice: The Earth's Long-Term, Global Average Energy Budget. Refer to the accompanying diagram, which shows the earth's long-term, global average energy budget for the atmosphere and the surface. Each numberon the diagram represents the rate (in Watts) at which energy arrives at, exits through, is reflected by, is absorbed by, or is emitted by a (horizontal) square meter. ("LWIR" = "longwave infrared radiation")

According to the diagram, what is the single largest source of energy for the earth's surface, by a wide margin? [Hint: look at the earth's surface and identify and compare its sources of energy, and ignore the sources of energy for the atmosphere.] (Select the one correct answer.)

The Earth's Long-Term, Global Average Energy Budget

  1. absorption of solar radiation
  2. reflection of solar radiation back to space
  3. evapotranspiration (which is mostly evaporation of water from oceans)
  4. emission of longwave infrared radiation by the surface
  5. absorption of longwave infrared radiation emitted downward by clouds and greenhouse gases in the atmosphere

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