Atmospheric Transmission Beer's Law

3/31/10Slant and vertical atmospheric pathsOptical depthz 2∫τ (z 1,z 2) =z 1β e(z) dzTransmittanceθ = solar zenith angle0º = overhead sun90º = sun at horizon€t = e − τ µNB. Optical depth does notdepend on the optical path,but the optical path andtransmittance do• Remote sensing is often done when the sun is not directly overhead, sothe radiation follows a slant path rather than a vertical path€Satellite viewing geometryµ is also referred to asthe (geometrical) airmass factor• Satellites measuring reflected and scattered radiation (UV/visible/SWIR)detect radiation that has been transmitted twice through the atmosphere18