METR 104:
Our Dynamic Weather

(Lecture w/Lab)
Thought Questions
on the Seasons
Dr. Dave Dempsey
Dept. of Geosciences
SFSU, Fall 2012

Prior Knowledge Required. Before starting these "Thought Questions", you should know the meaning of these terms:

Learning Objectives. When you are done responding to these questions and discussing them in class, you should be able to use figures such as Figure 2-5 to:

For the questions below, refer to the accompanying Figure 2-5.

  1. In Figure 2-5, how does the sun angle (the angle between the sun's rays and a horizontal surface) at solar noon generally vary with increasing latitude? What does this imply about the intensity of sunlight at high latitudes vs. low latitudes?

  2. Several globes are positioned around the room, simulating the position of the earth as it orbits the sun. (The sun is represented by an overhead or slide projector at the center of the orbit.) Notice that globes (should be) positioned so that the axis of rotation of each globe points in the same direction, just as it does (pointing toward Polaris, the North Star) when the real earth obits the sun.

    1. What time of year is it at the position of each globe? How can you tell?

    2. In Figure 2-5, which figure (a, b, or c) corresponds to each globe? Where do you have to position yourself next to each globe to see it as it is shown in its corresponding figure?

    3. At each time of year shown, how does the length of daylight seem to vary with latitude? How can you tell?

    4. Note the length of daylight (more than 12 hours, about 12 hours, or less than 12 hours) at San Francisco's latitude at each time of year shown. Does it seem to vary with time of year? If so, describe the variation.

    5. Note the sun angle at solar noon at San Francisco's latitude at each time of year shown. Does it seem to vary with time of year? If so, describe the variation.

  3. The seasons are defined in terms of variations in (a) length of daylight and (b) sun angle at solar noon. Why do these two quantities vary over the course of the year? At what latitudes does variation in length of daylight seem to be the greatest? What are the seasons like there, compared to here? (Note: seasonal variations in solar noon sun angle at different latitudes don't vary as simply, but they do contribute to seasonal variations in solar radiation, too.)

  4. Bonus Questions (there are many more such questions—the topic is very rich!):
    1. In Figure 2-5, in each of the figures (a), (b), and (c), when does the sun set (before 6 pm, at 6 pm, or after 6 pm)? When does it rise? How can you tell?

    2. In each figure, in what direction (on the horizon) does the sun appear at sunrise and sunset? Does this vary with latitude? [Hint: east is always in a direction along a latitude circle; north is along a longitude circle toward the N. Pole.]