Consider the absorption of 240 nm sunlight by O 2 . The O 2 cross section at thi
ID: 801780 • Letter: C
Question
Consider the absorption of 240 nm sunlight by O2. The O2 cross section at this wavelength is 10-24 cm2 molecule-1. Assuming that FTOA photons of this wavelengthe enter the top of the atmosphere, derive the equation for the attenuation of this light as a result of absorption of these photons as a function of altitude, neglecting scattering, for a solar zenith angle of 0 degrees. You may assume nair(0) = 2.6 x 1019 molecules cm-3 and the atmosphere scale height H = 7.4 km. As the sun moves lower in the sky, how does the absorption change?
Explanation / Answer
n (z) =nair(0) exp[-z/h]
n(z)=2.6*109 exp [-0/7.4km]
n(z) = 2.64*109 molecules cm-3