WAVELENGTHS ARE MEASURED FROM ONE CREST TO THE NEXT

RADIATION Radiation is he emanation of any part of the electromagnetic spectrum plus the release of particles

Where does the sun appear in the sky in summer and winter?

WHY WE HAVE SEASONS

The radiative properties of the material (most are selective in the wavelengths they absorb. 2. The amount of time the object is exposed to the emitted energy. The longer it is exposed the more energy it can absorb 3. The amount of the material. Very think objects may transmit and not absorb all the energy reaching them. Increasing thickness can increase the amount of energy it can absorb 4. How close the object is to the source of the energy. The further away, the less radiation reaches it. The less energy that reaches it the less it can absorb. 5. The angle at which the radiation is striking the object. Direct radiation is more concentrated than oblique and is absorbed more effectively A good absorber of radiation is also a good emitter of radiation at that same wavelength

EXAMPLES OF SOME ALBEDOS  Fresh snow 80-90 Thin cloud 30 Thick cloud 90 Ice 30-60 Grass 10-30 Water 10 Forest 10-20 Venus 78

STEFAN BOLTZMANN LAW E=σT4 E= maximum rate of radiation emitted by each square meter of surface area σ (sigma) is the Stefan Boltzman constant (2897 μmK – rounded to 3000 μmK) T=temperature in Kelvin to the 4th power A small increase in temperature yields a large increase in radiation since the temperature is raised to the 4th power. So a temperature increase of just 2 degrees increase the energy output by a factor of 16 (24)

Wien’s Law (or Wien’s Displacement Law) Wilhelm Wien, a German physicist showed that the wavelength at which the maximum radiation occurs is equal to Stefan Boltzman’s constant divided by the temperature in Kelvin λmax = constant/T in degrees Kelvin For the Sun: The sun’s surface temperature is about 6000K so we get   λmax=3000 μmK/ 6000K = .5μm (the wavelength where maximum radiation occurs) For the Earth: The Earth’s average surface temperature is about 300K (actually 288) λmax= 3000 μmK/ 300K = 10 μm (the wavelength where maximum radiation occurs)

Wear hat and apply SPF 15 sunscreen Exposure Category UV Index Protective Measures Minimal 0 – 2 Apply SPF* 15 Sunscreen Low 3 – 4 Wear hat and apply SPF 15 sunscreen Moderate 5 - 6 Wear hat, protective clothing and sunglasses with UV-A and UV-B protection. Apply SPF 15+ sunscreen High 7 - 9 Wear hat, protective clothing and sunglasses. Stay in shady area Apply SPF 15+ sunscreen Very High 10 Wear hat, protective clothing, sunglasses, apply SPF 15+ sunscreen avoid being in the sun between 10 A.M. and 4 P.M. * sun protective factor

UV--------visible---------------------------------------------------Infrared

Atmospheric window is between 8 μm and 11 μm

EARTH’S ENERGY BUDGET Starting with 100 units of short wave radiation 30% is reflected and scattered back into space This is the Albedo 20% is absorbed by atmosphere and clouds 50% is absorbed by the earth 100 units arrived 50 units gained by earth   The Earth gives off LONG WAVE radiation 7 units go into the atmosphere in convection 23 units lost by evaporation (latent heat) 20 unit net loss from 114 unit radiated to atmosphere with 8 absorbed to the atmosphere 94 reflected back and 12 units reflected back to space making a total of 20 units lost TOTAL 50 units radiated from Earth BUDGET BALANCED BUT WHERE ARE THE OTHER 50 units? 30 units are reflected by the atmosphere The ATMOSPHERE receives 20 units from the clouds 7 from convection 23 from condensation 8 units from the Earth (114 units radiated, 94 reflected back = 20; 12 go directly into space) 114-94 -12 = 8 TOTAL = 58 gotten LOSS Reflected 30 units from the sun 20 units absorbed by clouds 7 absorbed from convection 23 gotten from condensation 8 from earth radiation 58 units radiated back to space TOTAL ARRIVING 100 TOTAL LEAVING 100 EARTH’S ENERGY BUDGET

ATMOSPHERE== SURFACE== The 104 LW units from the surface is absorbed by the atmosphere and heats producing more LW units. The remaining 4 units are lost to space. The atmosphere emits 154 LW units; 66 of which head to space while 88 head back to the surface. The result is that the surface loses more than it gains (54 units) while the atmosphere also loses more than it gains (16 units) . This is an infinite cycle so the 88 units is radiated again reheating the air and retuning to earth and so on The balance (or lack) of long wave radiation between the surface, the atmosphere and space.

==SPACE ==ATMOSPHERE ==SURFACE SPACE== ATMOSPHERE== SURFACE== The 104 LW units from the surface is absorbed by the atmosphere and heats producing more LW units. The remaining 4 units are lost to space. The atmosphere emits 154 LW units; 66 of which head to space while 88 head back to the surface. The result is that the surface loses more than it gains (54 units) while the atmosphere also loses more than it gains (16 units) It is the absorption of the outgoing longwave radiation by the atmosphere that keeps the temperature where it is. If they were not there the temperature would vacillate wildly between day and night. The mean temperature on the Earth would be close to -18 C (0 F) than it is now, with the average temperature of 15 C (59 F) LOGWAVE SURFACE Energy is exchanged between the atmosphere and the surface of the planet. The greatest part of the emission is absorbed by the atmosphere which is better at absorbing thermal radiation than solar because of the water ad CO2 in the atmosphere. Even so a portion passes out in the 8 - 12 μm band which matches those radiated with the greatest intensity from the Earth.. The is called the ATMOSPHERIC WINDOW which is that part of electromagnetic spectrum that the atmosphere doesn’t absorb. CLOUDS however will absorb the long wave radiation hence CLOUDY NIGHTS DO NOT COOL OFF AS RAPIDLY AS CLEAR NIGHTS. THE CLOUDS ACT AS A BLANKET HELPING TO RETAIN HEAT  

Some variation exists in examples depending on where and when the readings are taken

The 117 radiated by the Earth is larger than expected because the Earth radiates energy for both sides of the globe (i.e. the day and night side) whereas the solar energy only strikes the side facing the sun. It gets 51 from the sun, but radiates 147. The 96 units comes from the infra-red returned to the earth from the atmosphere 96 + 51 from sun = 147. 117-96= 21 (infra red radiated – the 96 returning from the atmosphere So 7+23+21=51 – the amount arriving from the sun   It is the returning energy that warms the earth and keeps the temperature livable If the amount of CO2 and water vapor increase, the amount returning becomes greater and the average temperature rises. (Climate change or global warming)

The 117 radiated by the Earth is larger than expected because the Earth radiates energy for both sides of the globe (i.e. the day and night side) whereas the solar energy only strikes the side facing the sun. It gets 51 from the sun, but radiates 147. The 96 units comes from the infra-red returned to the earth from the atmosphere 96 + 51 from sun = 147. 117-96= 21 (infra red radiated – the 96 returning from the atmosphere So 7+23+21=51 – the amount arriving from the sun   It is the returning energy that warms the earth and keeps the temperature livable If the amount of CO2 and water vapor increase, the amount returning becomes greater and the average temperature rises. (Climate change or global warming)