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  Investigating Heat Budgets
 

Knowledge Base
You've been assigned a special project as a television meteorologist. As a part of an ongoing effort to educate viewers about Minnesota weather your television station wants you to develop a series of broadcasts about the heat budget of lakes. You need to develop heat budget information to educate viewers about how lakes might affect the local weather.

To introduce viewers to the subject matter, review daily and seasonal air and lake water temperatures changes. Begin by writing a one paragraph script that includes the following details:

Is air or water usually warmer in the early spring?

Does air or water retain heat longer in the fall?

Does air or water warm up more quickly early in the day?

Does air or water retain hear longer as night falls?

Experimental Design
Depth and area calculations are available for Ice Lake and Lake Independence (see Table below). Explain to viewers how to calculate heat budgets (in calories) and demonstrate that the heat budget changes in a lake throughout the day.

Ice Lake 
 
Lake Independence 
Depth Intervals (m)
Area at surface of this depth (m2)
 
Depth Intervals (m)
Area at surface of this depth (m2)
1 m
1.600E+05
 
1 m
3.290E+06
2 m
1.481E+05
 
2 m
2.875E+06
3 m
1.362E+05
 
3 m
2.625E+06
4 m
1.244E+05
 
4 m
2.275E+06
5 m
1.126E+05
 
5 m
1.925E+06
6 m
1.008E+05
 
6 m
1.675E+06
7 m
8.890E+04
 
7 m
1.350E+06
8 m
7.710E+04
 
8 m
9.750E+05
9 m
6.520E+04
 
9 m
7.000E+05
10 m
5.640E+04
 
10 m
4.200E+05
11 m
4.160E+04
 
11 m
2.050E+05
12 m
2.970E+04
 
12 m
1.560E+05
13 m
1.790E+04
 
13 m
1.310E+05
14 m
6.300E+03
 
14 m
1.100E+05
15 m
4.000E+03
 
15 m
9.000E+04
16 m
1.000E+02
 
16 m
7.000E+04
      
17 m
4.000E+04
18 m
1.000E+04

Data Collection
Collect the data you need to calculate heat budgets during a 24 hour period from Lake Independence and Ice Lake. Record this data in a table or some appropriate and useful format.

Data Management and Analysis
Calculate the amount of heat lost or gained (in calories) between periods when the RUSS gathered temperature data in the lakes. What was the source of energy for the heat gains? Where did the heat go when the lake heat budget demonstrated a loss of heat energy? How many calories were involved in the heat budget changes between each period of measurement?

Interpretation of Results
The television viewers have responded to your initial reports with the following questions. What is a reasonable response for each question?

  1. What happened to the energy that was given off when the lake's surface cooled?
  2. What happened to the energy given off by layers below the surface?
  3. How much total energy was released from the lake between 6 pm. and 2 am?
  4. How do the temperature changes in layers below the surface of the lake compare to temperature changes in the surface layer?
  5. How does the energy released from lakes affect local weather patterns and the surrounding environment?
  6. How might the size of the lake affect its impact on the weather and surrounding environment?
  7. Which lakes in Minnesota would probably affect local weather the most? How would they affect that local weather?
  8. Identify an example of a large lake outside the U.S. that might affect local weather. How you could find out more about the effects of this lake on the surrounding environment?
  9. A cubic centimeter of water requires 540 calories to boil (change from a liquid to a gas at 100°C). This is an example of the different amounts of energy required when matter changes state. How much energy would be required to boil off the top meter of the lake beginning at 2pm? Where would you get that much energy?
  10. When a cubic centimeter of water freezes (changes from a liquid to a solid at 0°C), 80 calories of energy are released. (When water changes state — liquid to solid — the amount of energy involved in the change is different than the amount involved in incremental changes in temperature while water is in the same state.) How much energy would be given off for the top meter of the lake to freeze if the freezing began at 2 am?
  11. How might the energy released from a lake when it freezes affect the surrounding environment?

Reporting Results
Develop a presentation to help your viewers understand the local relationships between weather and the temperatures of Ice Lake or the relationships between weather and the temperatures of Lake Independence. Your teacher will specify the presentation format: multi-media, written paper, TV script, video, or oral presentation.

 


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date last updated: Friday December 04 2009