Modeling Earth's Temperature


Summary

Students use the STELLA program to create hierarchies of models of increasing complexity to understand the absorption of solar energy by the Earth and its radiation of that energy back to space. They first assume that Earth is a perfect black body lacking an atmosphere, then move on to incorporate the fact that Earth reflects much of the solar radiation incident upon it, and later incorporate the fact that Earth has an atmosphere. Each time they build onto the model students evaluate the output and compare it to actual Earth surface conditions to see how well each model refinement captures the reality of the physics of heat absorption, exchange, and emission. A second lab asks students to take their STELLA model of an Earth with a two-layer atmosphere and code it into fortran.

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Learning Goals

The primary purpose of the Earth Energy Balance exercise is to convey the importance of starting out simply when creating models and adding complexity gradually.

Context for Use

This activity was developed for a class introducing dynamical systems modeling to upper level undergraduate students.

Description and Teaching Materials

Earth_Energy_Balance_Lab.pdf (Acrobat (PDF) PRIVATE FILE 13kB Jun13 05)

The Earth as simple blackbody:
Blackbody_Model_Image.pdf (Acrobat (PDF) PRIVATE FILE 126kB Jun13 05)
Blackbody_Model.STM ( PRIVATE FILE 79kB Jun13 05)
earth_energy_blackbody.f90 ( PRIVATE FILE 4kB Jun13 05)

The Earth as a blackbody with albedo:
Blackbody___Albedo_Model_Image.pdf (Acrobat (PDF) PRIVATE FILE 128kB Jun13 05)
Blackbody___Albedo_Model.STM ( PRIVATE FILE 80kB Jun13 05)
blackbody_plus_albedo.f90 ( PRIVATE FILE 4kB Jun13 05)

The Earth with a one layer atmosphere:
1_Layer_Atmosphere_Model_Image.pdf (Acrobat (PDF) PRIVATE FILE 140kB Jun13 05)
1_Layer_Atmosphere_Model.STM ( PRIVATE FILE 139kB Jun13 05)
one_layer_atmosphere.f90 ( PRIVATE FILE 7kB Jun13 05)

The Earth with a two layer atmosphere:
2_Layer_Atmosphere_Model_Image.pdf (Acrobat (PDF) PRIVATE FILE 155kB Jun13 05)
2_Layer_Atmosphere_Model.STM ( PRIVATE FILE 198kB Jun13 05)
two_layer_atmosphere.f90 ( PRIVATE FILE 5kB Jun13 05)

The Earth with a complex atmosphere:
Complex_Atmosphere_Model_Image.pdf (Acrobat (PDF) PRIVATE FILE 175kB Jun13 05)
Complex_Atmosphere_Model.STM ( PRIVATE FILE 208kB Jun13 05)
complex_atmosphere.f90 ( PRIVATE FILE 10kB Jun13 05)

The additional lab asking students to code their STELLA model in fortran:
energy_balance_model_lab_fortran.pdf (Acrobat (PDF) PRIVATE FILE 9kB Jun13 05)

Teaching Notes and Tips

Instructor Notes (Acrobat (PDF) PRIVATE FILE 65kB Apr10 06)

Assessment

Earth_Energy_Balance_Lab_Answer_Key2.pdf (Acrobat (PDF) PRIVATE FILE 183kB Jun13 05)
assignment_assessment__4.pdf (Acrobat (PDF) PRIVATE FILE 5kB Jun13 05)

References and Resources

The following are readings for this activity:
  • Graedel, T.E., and Crutzen, P.J., 1993, Atmospheric Change: An Earth System Perspective, New York: W.H. Freeman and Company, 446 p.
  • Harte, J., 1988, Consider a Spherical Cow, Sausalito, CA: University Science Books, p. 69-72, p. 160-167.