Earth s Energy Budget

Transcription

1 Earth s Energy Budget Compare and contrast the amount of energy coming from the Sun that is reflected, absorbed or scattered by the atmosphere, oceans, and land masses.

2 Understanding the lingo Reflected: the heat energy that is not absorbed by the surface Albedo: the percentage of solar energy reflected back by a surface Absorbed: The amount of heat energy taken into the substance Scattered: When light passes through a partly transparent material, such as the atmosphere or cloudy water, the light will leave the material in various directions.

3 Budgets 1. What is a budget? 2. What does it mean to balance a budget? The amount you put in should equal the amount you put out 3. What does it mean if you are in debt? You have spent more than you have put into your bank account bad thing!!!!

4 Earth s Energy Budget Earth doesn t have money to spend, but energy. 1. Where does Earth get most of its energy for the surface of the planet? The Sun 2. What type of energy does the sun give Earth? Electromagnetic waves We are going to walk through where the energy is going and how it eventually returns to space.

5 Step 1: The Amount Coming in With any budget we need a starting amount. Our starting amount is 100 units By the time we are done we should have 100 units of energy returning to space. As the energy enters the atmosphere it is in short EM waves. -30 units are lost when they are reflected back into space by the upper atmosphere. We show lost with a negative sign

6 Why is the sky blue? As the visible light passes through the atmosphere the gas molecules transmit all the colors except blue; the blue wavelengths are partly scattered.

7 Step 2: absorption How much do we have left of our 100 units after 30 units are lost to space? 70 units As the energy comes in it is absorbed by The atmosphere and clouds (water) = 20 units The Earth s Surface =50 units Land, water, plants, desert

8 Earth s Surface Absorption Each material on Earth has a different heat capacity. This mean each heats up at different rates and also release the heat at different rates. This heat absorption and release affects the environment near each type of surface

9 Example: environments near water vs. environments that have a lot of sand...desert Water takes a longer time to heat up and cool down because it has a higher heat capacity. Environments near large bodies of water benefit from the slow cool down of the water. The slow release of energy at night makes so the night time temperatures don t get as cold. Deserts heat up fast and cool down quickly because of the low heat capacity of sand. Make sure to bundle up at night in a desert!

10 Earth s Surface reflection (end 2:07) 50 units are absorbed on Earth s Surface; some is absorbed and some is reflected: 1. Of the light that strikes oceans, 75% of it is absorbed, so how much is reflected? 25% 2. Of the light that strikes rainforests, 85% of it is absorbed, so how much is reflected? 15% 3. Of the light that strikes Desert, 65% of it is absorbed, so how much is reflected? 35% 4. Of the light that strikes polar regions, 15 to 60% is absorbed, so how much is reflected? 40 to 85 %

11 Step 3: the release of energy from the surface Remember that energy coming into Earth is short wave EM waves. As that radiation is transferred into the ground it vibrates the atoms and the energy is then released or transferred as longwave radiation, IR rays. Since 50 units went into the surface 50 units need to come out. 1. What are four ways the 50 units of energy are transferred? conduction, radiation, convection, and evaporation

12 Radiation to the atmosphere -20 units are radiated as longwave length radiation, or IR rays from Earth s surface 8 units are absorbed by the atmosphere Also note that this heat transfer by radiation is constantly going back and forth between the atmosphere and the Earth s surface. -12 units escape to space

13 Convection and Conduction to the atmosphere - 7 units are transferred to the atmosphere by conduction and convection. Conduction: the energy is transferred by molecular contact between the Earth s surface and the gas molecules in the atmosphere. Convection: the energy is transferred as the warm, less dense air rises (taking the energy with it). Then it releases its energy to the upper atmosphere, which cools the air, so it becomes more dense and falls back to the surface of the Earth, there to be warmed by the surface and repeat the cycle.

14 Evaporation 1. Recall back to our latent heat lab when water was boiling. Was there a temperature increase during that time? No 2. Where was the energy going? Into the phase change 3. What caused the dips in the flat temperature line? The energy was staying with the escaped water molecules. Once there was more energy leaving the water than coming in the temperature decreased.

15 Evaporation continue The same process happens on a larger scale. As the sun s energy heats up any body of water it causes water molecules to escape as water vapor. The water vapor carries the heat energy with it into the atmosphere where it transfers it to the colder environment of the upper troposphere. Then the water starts to condense into water drops (latent heat is released during condensation), where eventually gravity pulls it down. -23 units are transferred into the atmosphere by evaporation

16 Running total 1. So far we have had how much energy has been release into space? 42 units 2. How much was release or transferred from the ground to the atmosphere? (hint: what is ) 38 units 3. How much was absorbed by the atmosphere originally when the energy came from the sun? 20 units 4. How much energy is there in the atmosphere? (hint: what is ) 58 units 5. For this to be a balance energy budget how much more energy should be released? 58 units

17 Step 4: atmosphere heat release to space Our final step is to release or transfer the energy to space from the atmosphere. -58 units are eventually transferred into space from the atmosphere.

18 Check 100 units in and 100 units out