GEOG221 Lab#2 Earth - Sun Geometry

Thinking about how net radiation works, which of the following values do you think would be closest to the overall average annual net radiation for the entire planet?

0 watts per square meter; (The global average net radiation must be close to zero over the span of a year. Earth's average temperature will rise if the average net radiation is above zero, and the temperature will fall if the average net radiation is below zero.)

At solar noon on the December solstice, Sam measures a Sun elevation angle of 50°. At what latitude is Sam?

26.5° N

At solar noon on the June solstice, Marie measures a zenith angle of 16.5°. At what latitude is Marie?

40° N

On November 1, which of the following latitudes has the longest period of daylight?

60° S

Which of the following pairs of continents receives the least amount of snow cover per year?

Africa and Australia; (These two continents receive the least amount of snow cover per year; only a few scattered locations found on these two continents even receive any snow at all.)

Which two continents have the greatest amount of snow cover per year?

Asia and North America; (These two continents, especially their most northern regions, have the highest snow cover during their winter seasons.)

When is the Sun directly overhead at 23.5° S?

December 21

On which of the following dates is day length longest at 50° N latitude?

July 1; (This date is closest to the June solstice, which is when locations in the Northern Hemisphere would have the longest period of daylight.)

The figure in the activity shows the Northern Hemisphere tilted towards the Sun, with the Sun's rays (yellow arrows) directly striking the Tropic of Cancer. Note that the circle of illumination at different latitudes, which indicates the length of day and night at those latitudes. If the circle of illumination cuts a latitude in such a way that the lighted portion is greater than the dark portion, days are longer than nights. When the darkened portion is greater, the reverse is true. Given these conditions, identify the effects of the three factors discussed above. Drag the labels to their appropriate targets, placing the descriptions of insolation in the targets of group 2 and all other descriptions in the targets of group 1.

Left Side from Top to Bottom: constant day length shorter days, longer nights constant night Right Side from Top to Bottom: longer days, shorter nights greater insolation intensity lesser insolation intensity Now you know why the Sun's heat seems more intense in summer than in winter. Since you're feeling the direct rays of the Sun, rather than angled radiation, it really is more intense! With this information, you'll know where to plan your winter vacation depending on whether you want to snow ski or water ski!

On what date do the Sun's rays strike directly at 3° S latitude?

March 15; (This date is just before the March equinox.)

Emma lives in Chicago (42° N). At solar noon, on a given date, she measures a solar elevation angle of 48°. What is the date?

March 21

On the March equinox, which occurs on March 20 or 21, the Northern Hemisphere experiences spring and the Southern Hemisphere has autumn. On the September equinox, which occurs on September 22 or 23, the reverse is true. After the spring equinox, in either hemisphere, days grow longer until reaching their maximum at the summer solstice. Then, they begin to shorten again until the autumnal equinox when daylength once again is equal to the length of the night. Days continue to shorten after this event until they are at their shortest at the winter solstice. Which of the following are true of equinoxes? Select the three that apply.

Solar declination at the equator 12-hour daylength at all latitudes Daylength decreases after autumnal equinox (As you have seen, the main characteristics of equinoxes are solar declination at the equator and 12 hours of day and night at all latitudes. The characteristics of equinoxes and solstices explain why daylight seems to linger longer from spring to summer and why some people try to find a cause to celebrate when they reach the winter solstice.)

Given that the area experiencing a solar eclipse receives a substantially reduced amount of insolation, which of the following best explains why solar eclipses do not play a major role in Earth's seasonal variations?

Solar eclipses are rare; (Not only are solar eclipses rare, but even when they do occur, they happen only over a very small portion of Earth's surface, for only a brief period of time, as shown by the movie. These factors explain why solar eclipses don't play a major role in Earth's seasonal variations.)

Why does the Northern Hemisphere have more positive values for net radiation in July as compared to the Southern Hemisphere in July?

The Northern Hemisphere receives more sunlight in July; (The incoming radiation from the Sun is higher during the summer months for the Northern Hemisphere, so this explains why the Northern Hemisphere has more positive values for net radiation in July as compared to the Southern Hemisphere in July.)

Which of the following is correct about the month of June?

The subsolar point reaches 23.5° North; (Every year, the latitude of the subsolar point gradually moves to 23.5° North by June 21 or so, which is the furthest north the subsolar point ever goes. This explains why the Northern Hemisphere's summer begins in June.)

Which of the following is correct about the month of December?

The subsolar point reaches 23.5° South; (Every year, the latitude of the subsolar point gradually moves to 23.5° South by December 21 or so, which is the furthest south the subsolar point ever goes. This explains why the Northern Hemisphere's winter begins in December.)

Drag the appropriate labels to their respective targets. Place the blue solstice characteristic labels in the blue targets and the pink solstice name labels in the pink targets. The yellow lines, of course, represent the Sun's rays.

Top from Left to Right: longer nights, shorter days Sun's declination, summer, Northern Hemisphere Midnight Sun Sun's declination, summer, Southern Hemisphere equal days, nights Bottom from Left to Right: June Solstice December Solstice (You can see that solstices mark the extreme points of the Sun's declination—the Tropic of Cancer in the Northern Hemisphere during the June solstice, and the Tropic of Capricorn in the Southern Hemisphere during the December solstice. The hemisphere experiencing the direct rays of the Sun experiences summer and the longest daylengths of the year, with its highest latitudes experiencing constant daylight, also called the "Midnight Sun." Days and nights at the equator remain approximately equal, as always. Earth's orbit around the Sun includes two other major positions of Earth relative to the Sun's rays, one transitioning to the June solstice and the other to the December solstice. Those two positions signal the start of the other two seasons of the year.)

What season is it in the majority of the areas experiencing the eclipse during the time of this video?

Winter; (The majority of the areas experiencing the eclipse in this video are located in the Southern Hemisphere, and the movie's description tells you the movie is from July. In July, it is summer in the Northern Hemisphere but it is winter in the Southern Hemisphere, as the two hemispheres are seasonal "opposites" of each other.)

Which aspects of seasonality are caused by either revolution or rotation? Select the three that apply.

length of a tropical year daily pattern of days and nights duration of the seasons Now you can see how Earth's revolution around the Sun and its rotation on its axis contribute to the duration of a year, its seasons, and the pattern of days and nights.

Which of the following terms would best describe the area within the white circle?

subsolar point; (The subsolar point is the point on Earth's surface where the Sun can be seen directly overhead, and solar declination is the latitude of the subsolar point. The farther you get from the subsolar point, the lower the Sun is in the sky where you are. In the video, the subsolar point is centered on the area with the highest amount of insolation.)

Each of the following contributes to seasons on Earth EXCEPT __________.

the distance between Earth and the Sun; (While this distance varies seasonally, it is not the primary cause for the seasons.)

In which of the following locations would you be most likely to find a yearly net radiation surplus?

the equator; (There is more energy coming in than going out at the equator, which results in a net energy surplus.)

Where must the moon be, relative to Earth's ecliptic plane, in order to produce a partial solar eclipse like the one shown in this video?

very close to Earth's ecliptic plane; (To produce a solar eclipse, the moon must be in a position in which it crosses Earth's ecliptic plane. The moon must also be in between Earth and the Sun at that time for a solar eclipse to happen.)

South America receives the vast majority of its snow during the months of July and August. Why is that?

winter; (During the months of July and August, the Southern Hemisphere, including South America, is experiencing winter.)