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# MY NASA DATA Lesson:

## Variables Affecting Earth's Albedo

Image courtesy Earth Observatory

Purpose:
To have students investigate one of the variables that affect the Earth’s albedo
Estimated Time for Completing Activity: 2-3 class periods
Learning Outcomes:
• collect data on Earth’s albedo from two surface types at the same latitude
• graph the differences in the data for the two locations over a period of two years
• use the data to calculate how much difference there is in Earth’s albedo between the two locations
• suggest reasons for the differences
Prerequisite
Tools
• MY NASA DATA website
• Google Earth or maps or atlas where latitudes and longitudes can be determined within 1 degree
Vocabulary:
Background:

Earth’s albedo is the fraction of incoming radiation (sunlight) that is reflected into space. The Earth has an average albedo, which describes how much sunlight is reflected on average for the whole planet and the whole year. That value is about 0.3. The Earth also has a local albedo, which determines how much of the Sun’s light is reflected from a particular place at a particular time. The local albedo depends on the particular local surface, which can change seasonally as vegetation changes. It also depends on more rapidly changing things such as snow and clouds.

For reference, the values of albedo range from 0 to 1, where a value of 0.0 absorbs all radiation that strikes its surface and a value of 1.0 represents a body that reflects 100% of the radiation that strikes its surface.

Fresh snow has an albedo ranging from 0.75 to 0.90.
Dry dark soil has an albedo of approximately 0.13.

Procedure:

Part I. Select locations to compare.
1. Go to the lesson links above and click on the ‘Live Access Server’ link.
2. You should automatically be prompted with data parameter choices, if not click on ‘Choose Dataset’ in the top left of the screen and select Atmosphere, Surface Cover ,and then Surface Scene Type (CERES SARB)
3. On the left side of the screen under ‘Line Plots’ select ‘Longitude’
4. In the Compass Rose boxes under the navigation map, enter 1 S and press the enter key, then enter in 5 W and 55 E in their corresponding locations. Be sure to click on the radio button next to ‘Update Plot’ at the top of the screen to view your new plot.
5. You should now see your updated plot. Be sure to print or save the plot for comparison later in the lesson.
6. Referring to the Scene Type key in the Links above, begin picking out the surface scene types for the Longitude line you have selected. You may want to zoom in on the navigation map in the upper left of the screen to see what features the line crosses.
7. NOTE: the date for this data set is fixed at February 1, 2006. This data set does not change that much over time, allowing you to make a comparison with the albedo data and still be able to draw accurate conclusions from the two sets.

Part II. Obtain local albedo data.
1. Go to the lesson links above and click on the ‘Live Access Server’ link.
2. You should automatically be prompted with data parameter choices, if not click on ‘Choose Dataset’ in the top left of the screen and select Atmospheric Radiation, Top of Atmosphere (TOA) All Sky ,and then Monthly TOA All-sky Albedo (ERBSSCAN)
3. On the left side of the screen under ‘Line Plots’ select: Longitude
4. In the Compass Rose boxes under the navigation map, enter 1 S and press the enter key, then enter in 5 W and 55 E in their corresponding locations.
5. Change the date to Feb, 1998. Be sure to click on the radio button next to ‘Update Plot’ at the top of the screen to view your new plot.
6. You should now see your updated plot. Be sure to print or save the plot for comparison later in the lesson.

Part III. Compare
Looking at the data for your two plots, begin to determine what relationship exists between surface scene type and albedo.

Questions:

1. What is the relationship between surface scene type and albedo? (Surface Scene Type Variable can be used interchangeably with biomes. A link can be found in the links section that covers biomes in greater detail.)

2. Were there any features along the line that helped you make the comparison? Explain.

3. When comparing your surface scene line plot to the surface scene type key in the links section, were there any discrepancies in what you think should be in those locations? Explain!

Extensions:

1. Ice has a high reflectivity. Choose a location over water that may or may not freeze during the winter, depending on the severity of the winter. Obtain the local albedo data for that location. Looking at the values in the winter, try to determine whether the water froze or not. Obtain the surface temperature data to see whether it agrees with your determination.

2. Repeat this activity using the Monthly TOA Clear-sky Albedo, which includes only the surface characteristics, not the effects of clouds on the reflection of sunlight. What can you learn about the surface type? About the importance of clouds?

3. Find out what you can on the CERES satellite and the Earth Observing System (EOS). What other satellites have been part of EOS? What instruments did each have on board, and what properties did they measure? When were they put into service, and how long were they operational? What was the importance of their measurements?

Lesson plan contributed by Carl F. Katsu, Fairfield, PA