Atmospheric Transmission Beer's Law

3/31/10Transmission spectrum of the atmosphere• At which wavelengths is the cloud-free atmosphere relativelytransparent? (Atmospheric windows)• At which wavelengths is the cloud-free atmosphere strongly absorbing,and which constituents are responsible for the absorption?• How do the extinction and scattering properties of clouds vary withwavelength?Transmittance1ConstituentAtmospheric compositionFraction (byvolume) indry airSignificantabsorption bandsNitrogen, N 2 78.1% -Oxygen, O 2 20.9% UV-C, MW near 60and 118 GHz, weak inVIS and IRH 2 O 0-2 % Numerous strongbands in IR; also MWnear 183 GHzRemarksHighly variable intime and spaceAr & inert gases 0.936% - monoatomicCO 2 370 ppm Near 2.8, 4.3, and 15µmIncreasing 1.6ppm/yearMethane, CH 4 1.7 ppm Near 3.3 and 7.8 µm IncreasingNitrous oxide, N 2 O 0.35 ppm 4.5, 7.8 and 17 µmCarbon monoxide, CO 0.07 ppm 4.7 µm (weak)Ozone, O 3 ~10 -8 UV-B, 9.6 µm19