The albedo is the fraction of radiation which reflects
off a body. In meteorology that body typically is the earth's surface
or clouds. The values for albedo differ from location to location and
even from day to day. The color and texture of the earth's surface
affect the albedo of a given location. Plants, clouds, rain and snow
affect the daily albedo. The primary result of a greater albedo is
a reduced ability for the surface to absorb solar radiation.
Objectives
Objectives
- Given a table of upwelling and downwelling shortwave radiaton data, the student will be able to compute the average albedo at an ARM/CART site.
- Given a table of upwelling and downwelling shortwave radiaton data, the student will be able to determine if the albedo changes at a given location throughout the year.
- Given a table of upwelling and downwelling shortwave radiaton data, the student will be able to hypothesize the reason(s) that albedo may change at a given location during the year.
- This activity should be conducted throughout the school year, about every fourth week. Obtain ARM upwelling and downwelling shortwave radiation data for the first week of each month. (If the first day of the month is a Thursday, Friday, or Saturday, skip to the next week). Use WxScope to create daily graphs or tables of these data.
- Divide the class into groups of 3 or 4 students. Assign each group a different station.
| PROCEDURE Albedo is the ratio of the reflected radiation to the incident radiation. To calculate the albedo, divide the upwelling shortwave radiation by the downwelling shortwave radiation. 1. Compute the albedo for your station at 8 AM, 10 AM, 12 PM, 2 PM and 4 PM. 2. Take the average of these five albedo values to determine an approximate daily average albedo. 3. Repeat steps 1 and 2 for the remaining 6 days of the week. 4. Average these daily averages to compute a weekly average albedo. 5. Repeat steps 1 to 4 every month until the month before the end of school. 6. After the last week of calculating albedos, create a graph of the weekly average albedos for a year. Be sure to label your axes. 7. Compare your graph with other groups. QUESTIONS 1. What is the average albedo of your station during the months that you computed weekly averages? 2. Does the albedo at your station change throughout the year? Why or why not? 3. How do the monthly albedos at your station compare with those of other groups? Are they consistently higher or lower? What could account for any differences? 4. As you were making your computations did you notice specific types of weather events that caused changes in the albedo during the day or week? If so, what? 5. What part of the day would the amount of energy lost by reflection from the earth's surface be the greatest? Why? 6. How does albedo affect the climate globally? List some examples of places that you think would have different average albedos and explain why they are different. |
PREREQUISITES
(Per person):
Albedo Incident radiation Reflected radiation CORE CURRICULUM SKILLS APPLIED IN THIS LESSON
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