Name:________________________________________________ Section:________________
Earth-Sun Geometry and Insolation
1. Calculate the declination, zenith angle, noon sun angle and radiation intensity (see Table 1.2) for Minneapolis, MN and Belize City, Belize for each date.
Latitude of
Zenith Noon
sun Radiation
Date Declination angle angle intensity
(%)
March
21 0 45 45 70.71
June
22 23.5N 21.5 68.5 ~92.4
September
23 0 45 45 70.71
December 22 23.5S 68.5 21.5 ~36.65
Latitude of
Zenith Noon
sun Radiation
Date Declination angle angle intensity
(%)
March
21 0 17.5 72.5 ~95.37
June
22 23.5N -
6 * 84 99.45
September
23 0 17.5 72.5 ~95.37
December 22 23.5S 41 49 75.47
* negative zenith means declination exceeds site latitude in
same hemisphere; this occurs only within the astronomical tropics. Treat as an absolute value.
2. Plot the values of the
Figure 1.4
Variation in
3. Which of the two locations above,
MINNEAPOLIS
4. Based on the information for
LOWER LATITUDE =
HIGHER SUN ANGLE = HIGHER INTENSITY
5. What effect might the amount
of change in
HIGHER SUN ANGLE
= HIGHER ENERGY = HIGHER TEMPERATURES
6. a. Would the sun appear to the north or south of an observer in each of these cities on June 21?
b. Where would the sun appear on December 22?
7. Why is there a difference in the direction that the sun appears in at these two places?
(I.E., JUNE 21ST DECLINATION IS GREATER THAN
8. Fill in the information for the following locations on December 22. Use an atlas to determine the latitude of each location and round the latitudes off to the nearest half degree. Use Table 1.3 to estimate [NcH1]the day length period.
Zenith Noon
sun Daylight
Location Latitude angle angle (hr:min)
Nasser
Lake, Egypt 23.5N 47 43 10:40
9. a. Plot the values of the noon sun angle (Y-axis) and latitude (X-axis) on the graph paper provided and connect the points with short line segments.
b. Plot the values of daylight (Y-axis) and latitude (X-axis) on the graph paper provided and connect the points with short line segments.
10. Using your answers to question #8 and #9 as an example:
a. How does the number of hours of daylight change as you travel from the North Pole to the South Pole on the June solstice?
from very long (continuous
daylight at the latitudes > 66.5N) progressively less to very short
(continuous night > 66.5S)
b. How does the
from 23.5 at the North Pole
up to 90 at 23.5N, then progressively downward until 0 at 66.5S, and negative
(below the horizon) at south latitudes >66.5
c. On the June solstice, at what latitude (approximately) would you expect to experience the warmest temperatures, and at what latitude (approximately) would you expect to experience the coldest temperatures?
warmest: around 23.5N
coldest: any > 66.5S
11. In which of the following cases will a beam of solar radiation be dispersed over the smallest surface area when it strikes the Earth's surface at the place and time indicated?
LAT DEC Zn
a.
b.
c.
d.
e.
