Geology 210: Activity 2 (5 pts) Energy Objective: To understand the earth’s glob

Question

Geology 210: Activity 2 (5 pts)

Energy

Objective: To understand the earth’s global energy budget

The following radiation measurements have been fabricated to represent mid-morning observations for a field of grass and an asphalt parking lot. Please show all of your work. Also, be sure to include the appropriate units with your answers!

Field of grass

Asphalt parking lot

Incoming solar radiation

1000 W m-2

1000 W m-2

Outgoing solar radiation

250 W m-2

50 W m-2

Incoming longwave radiation

310 W m-2

310 W m-2

Outgoing longwave radiation

440 W m-2

440 W m-2

1. What is the net radiation (in W m-2) of the field?

3. What is the albedo (in %) of the field?

5. Based on the net radiation, would you expect the temperature of the field to increase, decrease, or remain the same? Why?

2. What is the net radiation (in W m-2) of the asphalt?

4. What is the albedo (in %) of the asphalt?

6. Based on the net radiation, would you expect the temperature of the asphalt to increase, decrease, or remain the same? Why?

7. Which will eventually be warmer, the field or the parking lot? Why?

8. Why were the values for net radiation different for the two surfaces?

Note: Questions 8-10 are general questions about the net radiation formula and its components.

9. Is incoming solar radiation at a location, such as the roof of your home, ever 0 W m-2? Why or why not? Is it ever negative?

10. If the incoming shortwave radiation is 800 W m-2, what is the range of possible values of the outgoing shortwave radiation? Please explain.

11. Answer questions a-d to determine why net longwave radiation is generally negative.

What are the sources for incoming longwave radiation and outgoing longwave radiation in the radiation budget?

Which radiation law is used to determine the amount of radiation an object/surface emits?

Which variable determines the amount of radiation an object/surface emits?

Hopefully you have noticed from our examples that net longwave radiation is generally negative. Based on your answers above, what explains this?

12. As greenhouse gases are added to the atmosphere,

Which variable in the net radiation equation, Q = (K - K) + (L - L), would be affected first by the addition of greenhouse gases to the atmosphere?

Would the variable increase or decrease?

Why would that change occur?

What implications does this have for Q and surface temperatures?

Field of grass

Asphalt parking lot

Incoming solar radiation

1000 W m-2

1000 W m-2

Outgoing solar radiation

250 W m-2

50 W m-2

Incoming longwave radiation

310 W m-2

310 W m-2

Outgoing longwave radiation

440 W m-2

440 W m-2

Explanation / Answer

Question 1: Net radiation in the field : Q = (shortwave incoming - shortwave outgoing) + (longwave incoming - longwave outgoing). =(1000-250) + (440-310) = 880 W m-2 Question 2: Net radiation in the asphalt : = (1000-50) + (440-310) = 950 + 130 = 1080 W m-2 Question 3: Albedo for grass = net radiated solar radiation / net incoming radiation = (250 + 440) / (1000+310) x 100 = 0.496 x 100 49.6% Question 4: Albedo = (50+440)/(1000+310) x 100 = 0.374 x 100 =37.4%

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