1. SOLAR ENERGY ► Solar energy is transmitted to earth in the form of short and long wave (SW and LW) radiation. SW is light. LW is heat. Incoming Solar Radiation, or INSOLATION is the energy which drives the atmospheric system. Wien’s Law:  max = C/T Where  is the wavelength of most intense radiation, C = 2897  m/K and T is the temperature in Kelvins (K)

2. Radiation Basics SW LW The sun emits all types of radiation. Anything above 700 nm is Long Wave (LW). Below 700 nm is Short Wave (SW).

3. max  = C/T = 2897  m K /288 K = 10  m 1  m = 1000 nm

4. max  = C/T = 2897  m/K /6100 K  0.5  m

5. Stefan-Boltzmann’s Law E =  T 4 where E is the energy emitted,  is a constant ( ), T is the temperature in Kelvins (K) = 5777 K (http://solarsystem.nasa.gov/planets/sun/facts) This works for perfect emitters (blackbodies) like the sun. E is the area under the curve E = 5.67 x 10 -8 W m -2 K -4 x (5777 K) 4 = 6.315 x 10 7 W m -2 Surface area = 6.08 x 10 18 m 2 Total Energy = 3.84 x 10 26 Watts This is what is emitted by the sun. But at the surface of the Earth that is not how much energy is absorbed.

6. Solar radiation spreads out evenly in all directions So, the total radiation from E =  T 4 gets spread out over a sphere with the radius of the Earth’s orbit. What is the energy/unit area at the Earth’s mean orbital radius? Not to scale, of course The orbit is not a circle but the mean radius is 1.495 x 10 11 m Area of a sphere = 4  r 2 Ans: Area = 3.84 x 10 26 W/ 2.81 x 10 23 m 2 = 1367 W m -2 = 1.98 cal cm -2 min -1

7. What happens to the insolation when it gets to the Earth? A given amount of radiation covers a smaller area when overhead than when at a low angle; it is more concentrated

8. The low sun (near sunset) shows more red due to atmospheric dust and pollution. More of the SW radiation is being absorbed and scattered away. In addition to spreading out at low sun angles, the insolation must travel through more atmosphere

9. Seasonal effects on sun angle and insolation 91,000,000 miles94,000,000 miles Aphelion Perihelion

10. The time of year causes the sun’s angle in the sky and the amount of daylight

11. Depending on your latitude, the sun’s trajectories across the sky are very different

12. DAY LENGTH Antarctic circle 66.5°S Arctic circle 66.5°N North Pole 90°N South Pole 90°S Equator 0° Tropic of Cancer 23.5°N Tropic of Capricorn 23.5°N Six months daytime (March-Sept), six months night (Sept - March) Six months daytime (Sept - March), six months night (March-Sept) One day with 24 hours daylight (June 21st); one day with 24 hours darkness (Dec 21st) One day with 24 hours daylight (March 21st); one day with 24 hours darkness (June 21st) Sun is overhead once a year (June 21st). Day length always at least 10 hours. Sun is overhead once a year (Dec 21st). Day length always at least 10 hours. Constant day length - 12 hours day and night all year round Lengths of day and night vary more between the seasons at higher latitudes. This makes climate more seasonal at the poles than the equator More seasonal

13. Radiation Exercise (Practice) You are marooned on a tropical island somewhere in the Pacific Ocean. You don’t know where. You have built a boat to escape but you only have food and fresh water for 2 days so you must get to land in that time or die. So you need to know where you are now to decide the right direction to go. Like the movie “Castaway”, you have a watch always set to Memphis time. On the island, you have no tools, no compass, no telescope. You have the sun. This is your island (it’s the one from Castaway)

14. Split into groups of 3-4. Brainstorm ideas of what you could do. For now, you don’t have to do any calculations. You must, however, come up with a plan which may involve calculations. You want to know as precisely as you can, where you are and what direction to go once you are in the boat on the ocean. After 15-20 minutes, each group presents their plan. The most workable plan (as determined by your professor) will be the one the class uses. Once you have the plan, an assignment will be made to actually put the plan into action to determine your location and a suitable direction. You have until Feb 2 to execute the plan, make your determinations, and write it up scientifically, i.e., include a statement of the problem, your method for solving it, your solution, and final conclusions. Keep this to 1- 2 pages. Procedure

16. Energy must be transferred from Equator to Poles

17. Global Energy Flux Polewards of 40°N and S, there is an annual heat deficit. Equatorwards of 40°N and S, there is an annual heat surplus. Without movement of heat energy, the poles would become steadily colder and colder, while the equator would get progressively warmer. This clearly does not happen. This heat transfer (flux) occurs by: Ocean currents; cold polar water flows towards the equator while warm water flows from equator to pole. Air mass movements and storms which blow warm air towards the poles and cold air towards the equator. Also, winds transport poleward water vapor which releases latent heat upon condensing in the cooler air. An excess of evaporation which takes up and stores latent heat in water vapor, releasing it towards the pole where it condenses.

18. OCEAN CURRENTS ColdSea temperature Warm Labrador current carries cold water from equator to pole down east coast of N.America Gulf Stream carries warm water from equator towards the pole, and NW Europe A similar counter-clockwise movement of warm water polewards, and cold water equatorwards can be seen in the Pacific. Surface currents generally do not cross the Equator.

19. From http://www.ncdc.noaa.gov/paleo/ctl/thc.html The surface currents connect with deep ocean currents to form the thermohaline circulation.

20. Air Masses

21. Heat Transfer by Humidity POLES - Precipitation exceeds evaporation at high latitudes; condensation releases latent heat stored in water vapor. EQUATOR - Evaporation exceeds condensation (and precipitation); this uses heat energy and stores it in the form of water vapor. Red shows high humidity from high rates of evaporation

22. Cold, north winds blowing south. Warm south winds blowing north. A typical situation that helps correct the energy imbalance. Winds

23. Jan 20-22, 2014

24. Energy Budget What comes in versus what goes out.

25. Having an atmosphere introduces clouds, reflection, and scattering.

26. Albedo is reflection. Low albedo is not very reflective. Reflection is pretty intuitive but albedoes are not always obvious (see water) As a whole, the Earth- atmosphere-ocean has an albedo of 30%

27. Scattering is molecular. Unlike reflection, it happens in all directions, even forward. Absorption is just what it sounds like. The radiation is absorbed. But after that, the absorbing body’s temperature rises so it emits radiation in accordance with the Stefan-Boltzmann and Wien’s laws.

28. The Earth’s Energy Budget is Balanced (not always true for people)

29. How does radiation lead to temperature climatology? Next: