Seasonal Solar Input Project: Angle of InSOLation Lab
Lab: Part A
Background Information
In the narrow sense of the word, Climate is the average or typical state of the weather at a
particular location and time of year. Its description includes the average of such variables as
temperature, humidity, windiness, cloudiness, precipitation, visibility etc., and also the expected range
of the deviations of these variables from the mean. In the broadest sense however, climate is the
state of the Earth's habitable environment consisting of the following components and the
interactions between them:

The atmosphere, the fast responding medium which surrounds us and immediately affects our
condition.

The hydrosphere, including the oceans and all other reservoirs of water in liquid form, which are the
main source of moisture for precipitation and which exchange gases, such as CO 2, and particles, such
as salt, with the atmosphere.

The land masses, which affect the flow of atmosphere and oceans through their morphology (i.e.
topography, vegetation cover and roughness), the hydrological cycle (i.e. their ability to store water)
and their radiative properties as matter (solids, liquids, and gases) blown by the winds or ejected from
earth's interior in volcanic eruptions.

The cryosphere, or the ice component of the climate system, whether on land or at the ocean's
surface, that plays a special role in the Earth radiation balance and in determining the properties of
the deep ocean.

The biota - all forms of life - that through respiration and other chemical interactions affects the
composition and physical properties air and water.
In our generation climate is receiving unprecedented attention due to the possibility that
human activity on Earth during the past couple hundred years will lead to significantly large and
rapid changes in environmental conditions. These changes could well affect our health, comfort
levels, and ability to grow and distribute food.
APES introduces the climate system and the processes that determine its state as a
problem in physical science. Our goal is to explain the properties of the climate system and its
governing processes in a quantitative manner, so that a better understanding of today's
environmental issues can be achieved. While APES is mainly concerned with the properties of
atmosphere and hydrosphere and the physical laws governing their behavior, attention to the solid
and living earth will also be given in another part of this lab, as far as they affect atmosphere and
hydrosphere.
Within the climate system the atmosphere plays the role of the efficient communicator.
The atmosphere is capable of quickly moving and distributing mass and heat over large distances,
horizontally and vertically and spread the effect of frequent perturbations to remote regions of
the globe within hours to days from their occurrence. The atmosphere directly affects life on
Earth by supplying the gases for the respiration of vegetation and animals and by moving water
from oceanic regions to be deposited in liquid or solid form on land. The atmosphere also shelters
life on Earth from the extreme and potentially harmful effects of direct solar radiation. The
oceans are most important because of their tremendous heat storage potential and their ability to
distribute that heat horizontally. The composition and motion of the water in the hydrosphere
sustains a rich and diverse life system. The exchange of gases and heat between oceans and
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A
atmosphere determines the physical properties and composition of both these sub-systems and is
one of the primary climate processes.
We begin APES in a study of solar radiation, the primary energy source for Earth and its
climate system. We examine the properties of the Sun and its energy and the laws governing the
transfer of this energy through space from the Sun to the Earth. We then study in detail the
transformation of this solar energy on Earth and gain first appreciation on how this energy shapes
the properties of Earth's climate.
Energy from the Sun.
The energy that drives the climate system comes from the Sun. When the Sun's energy reaches the
Earth, it is partially absorbed in different parts of the climate system. The absorbed energy is converted back
to heat, which causes the Earth to warm up and makes it habitable. Solar radiation absorption is uneven in both
space and time and this gives rise to the intricate pattern and seasonal variation of our climate. To understand
the complex patterns of Earth's radiative heating we begin by exploring the relationship between Earth and the
Sun throughout the year, learn about the physical laws governing radiative heat transfer, develop the concept
of radiative balance, and explore the implications of all these for the Earth as a whole. We examine the
relationship between solar radiation and the Earth's temperature, and study the role of the atmosphere and its
constituents in that interaction, to develop an understanding of the topics such as the "seasonal cycle" and the
"greenhouse effect". We complement this lecture by a set of two laboratory assignments that explore in much
more detail the spatially and seasonally varying elements of the Earth radiation budget as they are revealed
through satellite observations of the Earth.
This lab will help you understand and also address some of the common misconceptions about seasons and
climate. The fallacy held by many graduates and faculty from Harvard University is that summer in the northern
hemisphere occurs when the Earth is closer to the Sun, a position known as “perihelion”.
Actually, the opposite is true. The position at which Earth is closest to the Sun occurs
during winter in the northern hemisphere. Earth is actually physically farther from the
Sun during “Aphelion”. This is Summer in the Northern Hemisphere.
The seasons occur because of differences in the intensity of sunlight at various
latitudes due to the Earth’s 23.5° tilt. As seen in the figure to the right, the sun’s rays
are nearly parallel as they reach the surface of the Earth. The same amount of energy is
found in each of the groups of rays, from group A, to group B, as each pair of lines is the
same distance apart. Both groups start at the same latitude above and below the
equator. Due to the tilt of the Earth, the area covered by group A is greater than B. The
northern hemisphere is therefore cooler and therefore experiencing winter. Group A
would be at winter solstice, while group B would be at summer solstice, whereas halfway
in between group A and B would be the spring or fall equinox.
This lab will address the changes in amount of energy available to heat water as the seasons change. This
lab project will continue on a monthly basis from now, through winter solstice and then back to spring equinox.
Materials
Temperature probe
Black Container with Lid
250 mL beaker
Graduated cylinder
Chilled water
2 meter sticks
Calculator
Styrofoam plate
timer
Poor-Man’s Clinometer
Procedure
Create two data tables similar to the one below; however give yourself room for many more rows, as you will be
continuing to collect monthly data until just after the spring equinox. You will be collecting this data as an
individual, and sharing it to get class averages, so you will need two tables in order to get the class data as well.
1.
indicate the weather conditions as sunny, mostly sunny, mostly cloudy, or cloudy in data table
2. take and record ambient temperature using the probeware. Record in data table
3. find an area that is not near buildings and will not be blocked by shadows
a. place your energy absorbing black container on the insulated Styrofoam plate
b. carefully place temperature probe and 200 mL of chilled water into container
2
A
B
B
c.
4.
5.
Date
start timer and determine time needed to obtain a 10 degree temperature change

set up a proportion, if it takes 25 minutes to go up 3º, how long will it take to go up 10 º?
d. put data into class data table, and determine the average of the data from all participants
find the angle of inclination using the two meter stick method
a. hold one of the meter sticks vertically so that it makes a shadow on the ground
b. record the length of the shadow, using the other meter stick
c. divide the length of the meter stick by the length of the shadow using the same units. (cm. M,
mm)
d. determine the angle by taking the tan-1 of this ratio
e. put average group data in data table, determine the average data from all class participants
f. use your clinometer to determine the angle of insolation manually. Put that information in your
data table too. How close was your calculation to your clinometer reading? (Don’t forget to
subtract from 90 degrees.)
calculate the number of days before (-) or after (+) winter solstice (December 21, 2010) and put this
information into the data table also.
Weather Conditions
Ambient
Temperature
Days from Winter
Solstice (+/-)
Class Average
Time for
Temperature
Change
Class Average Angle of
Inclination
Tan-1
Manual
Please address analysis questions in April, when lab is
complete.
Analysis Questions:
1.
2.
Was everyone’s time for the temperature change the same? Why did you average all the values?
Graph the data from your data table, using days from winter solstice as x-axis
a. Use average time for temperature change as the y-axis putting labels on the left side of the
graph
b. Use average angle of inclination as the y-axis putting labels on the right side of the graph
c. Make sure that the maximum for angle of inclination is the same height as the maximum for
time for temperature change
3. What is the general shape of the data of each graph? Why?
4. What happens to the angle of insolation and time for temperature change on Autumnal Equinox? Winter
Solstice? Vernal Equinox? Using this information, hypothesize about what might happen to the angle of
insolation and time for temperature change on the Summer Solstice.
5. Explain any relationship between your latitude (or longitude) and the angle of the light. In other words,
would your results be much different if you were in Anchorage Alaska?
6. What physical factors about the planet Earth cause the changes seen in the intensity and angle of the
light?
7. What are the changes in biomes associated with the change in the intensity and angle of the light?
8. How has this influenced the characteristics of the organisms, especially the producers in the area?
9. How does this influence the primary productivity and agriculture?
10. Do these results make any suggestions as to why global climate change is causing a greater temperature
change in the arctic versus the equatorial regions? Why or why not?
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