Energy in the Earth System
Question 1: Explain the equilibrium of the Earth’s energy budget.
Answer 1: The Earth can be considered as a physical system with an energy budget that includes all gains of incoming energy and all losses of outgoing energy. The Earth is approximately in equilibrium, so the sum of the gains should be approximately equal to the sum of the losses.
There are lots of good resources about Energy that you can find available.
Question 2: Compare and contrast Earth and Mars.
Answer 2: There are amazing similarities between the Martian atmosphere that exists today and the atmosphere that existed on Earth billions of years ago. When the Earth was first formed, no oxygen existed on our planet, and it, too, looked like a desolate, unlivable planet. The atmosphere was made entirely of carbon dioxide and nitrogen. It wasn’t until photosynthetic bacteria developed on Earth that enough oxygen was produced to allow for the development of animals. Similarly, the thin Mars atmosphere today is almost totally composed of carbon dioxide. Here is the composition of Mars’s atmosphere: 95.3 nitrogen, 1.6 oxygen. In contrast, Earth’s atmosphere consists of 78.1 oxygen, 0.9 carbon dioxide and other gases. The similarity of the early Earth and modern Mars atmospheres has led some scientists to speculate that the same process that turned the Earth’s atmosphere from mostly carbon dioxide into breathable air could be repeated on Mars. To do so would thicken the atmosphere and create a greenhouse effect that would heat the planet and provide a suitable living environment for plants and animals.
Question 3: Discuss Earth’s outgoing energy.
Answer 3: The average reflectivity of the Earth is about 0.3, which means that 30 is absorbed by the Earth and reradiated as infrared. The planet’s reflectivity varies from month to month, but 0.3 is the average figure. It also varies very strongly spatially: Ice sheets have a high reflectivity, oceans low. The contributions from geothermal and tidal power sources are so small that they are omitted from the following calculations: 30 reflected from the atmosphere, 20 reflected from the ground (including land, water and ice). The remaining 70 51 is transferred back into the atmosphere as latent heat by the evaporation of water, 7 is radiated directly into space, and 15 is absorbed by the atmosphere and clouds, including 16 transferred to clouds, from where it is radiated back into space. (When the Earth is at thermal equilibrium, the same 70 64 by the ground.
Previous: Energy and Power Technology, Part 5 - Next: Energy Resources and Consumption, Part 1
|
