Atmospheric Transmission Beer's Law

More documents

Recommendations

Info

3/31/10Measuring solar intensity from the ground• Now take the logarithm of both sides:• Define x = 1/µ = sec θ then this is a linear equation of the form y = mx+c,where y = ln(I λ ), the slope m = -τ λ and the y-intercept c = ln(S λ ).• Hence to determine τ λ and S λ , measure y for a range of values of x, i.e. atdifferent times of day as the sun rises, reaches its zenith, and sets. Plot thedata and find the slope and y-intercept.(θ = 0º)Sun photometerhttp://aeronet.gsfc.nasa.gov/Global network of sun photometers measuring aerosol optical depthCalibrated using Langley technique at Mauna Loa Observatory, Hawaii24
3/31/10The exponential atmosphere• The density of the atmosphere decays exponentially with height z:ρ(z) = ρ 0e − z H• Where ρ 0 is the density at sea level and H (≈ 8 km) is the scale height (thealtitude change that leads to a factor e change in density)• So for a ‘well-mixed’ constituent (like CO 2 ), its density is:€• where w 1 is the mixing ratio (mass of constituent per unit mass of air)• Assume a mass absorption coefficient k a for the constituent that dependson λ but not T or P, and a nonscattering atmosphere at the λ of interest:€ρ 1(z) = w 1ρ 0e − z Hβ e(z) = k aw 1ρ 0e − z H€Optical depth in an exponential atmosphereτ (z) =∞∞∫ β e( z ʹ′ )dz ʹ′ = k aw 1ρ 0 ∫ e − ʹ′zzz Hdzʹ′τ (z) = k aw 1ρ 0He − z H€Optical depth between altitude z andthe top-of-the-atmosphere (TOA)€τ* = τ (0) = k aw 1ρ 0HTOTAL <strong>Atmospheric</strong> Optical Depth€Optical depth increases more rapidlytowards the surface25
Page 1 and 2: 3/31/10Atmospheric TransmissionBeer
Page 3 and 4: 3/31/10Extinction of radiation• A
Page 5 and 6: 3/31/10• β e = β a + β sExtinc
Page 8 and 9: 3/31/10Properties of Beer’s Law
Page 10 and 11: 3/31/10Optical depth problemThe opt
Page 12 and 13: 3/31/10More Beer’s LawNow taking
Page 14 and 15: 3/31/10Deviations from Beer’s Law
Page 16 and 17: ONREMOTE CONTROLTX IN RX IN PPS-CON
Page 18 and 19: 3/31/10Slant and vertical atmospher
Page 20 and 21: 3/31/10Atmospheric transmittanceUV-
Page 22 and 23: 3/31/10Extinction and scattering by
Page 26 and 27: 3/31/10Mass pathτ (z) = k aw 1ρ 0
Page 28 and 29: 3/31/10Optical thickness and transm
Page 30 and 31: 3/31/10The Aerosol Indirect Effect

Atmospheric Transmission Beer's Law

Create successful ePaper yourself

Delete template?

Save as template?