• Speed of light = wavelength () x frequency = 3 x 108 m/s in vacuum• Wavenumber = 1/ wavelength ( cm-1)• Frequency in GHz (1 Hz = sec –1)

Language of the Energy Cycle:The Electromagnetic Spectrum

EnergyWavelength

1. Power Source: Blackbody Radiation Planck’s Law:The amount and spectrum of radiation emitted by a blackbody is uniquely determined by its temperature

Max Planck (1858 – 1947) Max Planck (1858 – 1947) Nobel Prize 1918Nobel Prize 1918

Emission from warm bodies peak at short wavelengths

wavelength

620 K

380 K

Solar Spectrum = Shortwave spectrum=visible spectrum:

Sun at 6000K; peak emission at 0.5 m

CO2 H2OO3

Terrestrial Spectrum = Longwave Spectrum = Infrared Spectrum = Thermal Spectrum: Sahara Desert on Nimbus 4 Satellite

Theoretical Planck curves:Earth ~300K, peak emission ~15 m

Electromagnetic Spectrum

High energy

Short wavelength / high frequency

Emitted at high T

SunEarth

Vibrational Modes for CO2

C OO

CO O

O OC

symmetric

bending 15 m

asymmetric 4.3 m

Greenhouse effect: Radiation at specific wavelengths excite CO2 into higher energy states: energy is “absorbed” by the CO2 molecules

2. What happens to the radiation in the atm?

Other Greenhouse Gases

O

O O

O

H H

water ozone

N NO C

H

H

H H

methaneNitrous oxide

Absorption

Transmission

Atmosphere: Characteristic Absorption/Transmission for different atm molecules for l: 0-15 µm

Earth Spectrum

Incoming from Sun:High energy,

short wavelength

Outgoing from EarthLow energy

Long wavelength

0.5 m

10 m20 m

Earth’s Energy Balance

50

COCO22, H, H22O, GHGO, GHG

100

Shortwave Longwave