METR 104:
Our Dynamic Weather
(Lecture w/Lab)
Pre-class Quiz #2:
for on-Line Reading #2
Dr. Dave Dempsey
Dr. Oswaldo Garcia
& Denise Balukas
Dept. of Geosciences
SFSU, Fall 2012

This is a "preview" version of Pre-class Quiz #2, which is based on on-line Reading Assignment #2 and Reading #2 from the text. 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. Wednesday, Sept. 26. (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 seven questions below (two multiple answer and five multiple choice) address points made about the relationship between the earth and the sun in on-line Reading Assignment #2 and Reading #2 from the text.

The Questions:


(1) Multiple Answer. The Troposphere. Which of the statements below apply to the troposphere? (Select the one or more correct answers; there might be more than one.)

  1. it is the lowest of the four major atmospheric layers defined by the long-term, global average vertical profile of temperature in the atmosphere
  2. it averages about 11 or 12 km (6.9 or 7.5 miles) deep, though the depth varies a lot between the tropics and the poles
  3. it contains about 80% of all air molecules in the atmosphere
  4. the temperature within it decreases rapidly with increasing altitude, by a total of over 120°F (67°C) from sea level to the tropopause
  5. it contains the highest concentrations of ozone in the atmosphere (the ozone layer)
  6. it contains most of what we consider "weather" (clouds, precipitation, storms)
  7. unlike the stratosphere, air within it mixes vertically ("turns over") very well

(2) Multiple Choice. Earth's Closest Approach to the Sun. The earth's orbit around the sun is not a perfect circle but is slightly elliptical. As a result, the distance between the earth and the sun varies over the course of the year, by about 3% between its closest point and farthest point. At what time of year is the earth closest to the sun? (Select the correct answer.)

  1. early January (not long after the December solstice)
  2. late March (around the time of the March equinox)
  3. early July (not long after the June solstice)
  4. late September (around the time of the September equinox)

(3) Multiple Answer. Light Beam on a Flat Surface. When you shine a flashlight on a flat surface a few feet away, what happens to the light on the surface when you change the angle between the light beam and the surface (while keeping the distance between the flashlight and the surface the same)? (Select the one or more correct answers; there might be more than one.)

  1. Some of the light reflects from the surface and into our eyes, which is how we can see it. This is true to one extent or another at any angle between the light beam and the surface.
  2. When the beam of light strikes the surface at a lower angle, the light spreads out on the surface more, covering a larger area and becoming diluted so that it isn't as bright (intense).
  3. When the beam of light strikes the surface at a lower angle, the flashlight is closer to the surface and so the light is brighter (more intense).
  4. When the beam of light strikes the surface at a lower angle, the light reflects better and appears brighter (more intense).
  5. When the beam of light approaches the surface at a lower angle, the light passes through more air before striking the surface and so becomes dimmer (less intense) by the time it strikes the surface.

(4) Multiple Choice. Sun Angle and Intensity of Solar Radiation: Effect of the Atmosphere. How does the atmosphere affect the intensity of solar radiation reaching the earth's surface? (Select the best answer.)

  1. The atmosphere is transparent and so has little effect on solar radiation reaching the earth's surface.
  2. The atmosphere reduces the amount of solar radiation reaching the earth's surface, by the same percentage everywhere.
  3. The atmosphere reduces the amount reaching the earth's surface, and the lower the sun angle the greater the percentage reduction.
  4. The atmosphere reduces the amount of solar radiation reaching the earth's surface, by a percentage that is greater at low latitudes than at higher latitudes.
  5. The atmosphere focuses solar radiation on the surface, amplifying it by about the same percentage everywhere.

(5) Multiple Choice. June Solstice: Latitude Where Sun Is Directly Overhead. The time of day when the sun reaches its highest point in the sky is called solar noon. (Note that noon on your clock and solar noon are not usually quite at the same time because of the way that time zones are set up, and it's even farther off when we go on daylight savings time.)

On the day of the June solstice (June 21 or 22), at what latitude does the sun appear directly overhead at solar noon? (Select the correct answer.)

  1. everywhere (at all latitudes)
  2. on the equator (0° degrees latitude)
  3. on the Tropic of Cancer (23.5° North latitude)
  4. on the Tropic of Capricorn (23.5° South latitude)
  5. on the Arctic Circle (66.5° North latitude)
  6. on the latitude of San Francisco (about 37.5° North latitude)

(6) Multiple Choice. Minimum Solar Radiation. At what time of year do latitudes in the Northern Hemisphere experience both (a) the fewest number of hours of daylight, and (b) the least intense solar radiation at solar noon? (Select the correct answer.)

  1. on the day of the March equinox (March 21 or 22)
  2. on the day of the June solstice (June 21 or 22)
  3. on the day of the September solstice (September 21 or 22)
  4. on the day of the December solstice (December 21 or 22)
  5. There is no single day when the length of daylight and the intensity of solar radiation at solar noon are both at a minimum—they reach minima on different days.

(7) Multiple Choice. Twelve Hours of Daylight. At what latitude(s) is the sun above the horizon (daytime) for 12 hours and below the horizon (nighttime) for 12 hours, every day of the year? (Select the correct answer.)

  1. All latitudes experience 12 hours of daylight and 12 hours of night every day of the year.
  2. The Northern Hemisphere experiences 12 hours of daylight and 12 hours of night every day of the year, while the Southern Hemisphere experiences the opposite.
  3. The equator (0° latitude) experiences 12 hours of daylight and 12 hours of night every day of the year.
  4. The Tropic of Cancer (23.5° North) and the Tropic of Capricorn (23.5° South) experience 12 hours of daylight and 12 hours of night every day of the year.
  5. The Arctic and Antarctic Circles (66.5° North and South, respectively) experience 12 hours of daylight and 12 hours of night every day of the year


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