Calculate transmission / reflectivity instead of absolute quantities. For irradiances / actinic fluxes the transmission T is defined as

$\displaystyle T = {{E}\over{E_0 \cos{\theta}}}$ (0.1)

where $ E$ is the irradiance / actinic flux, $ E_0$ is the extraterrestrial flux, and $ \theta$ is the solar zenith angle. The reflectivity R is defined as

$\displaystyle R = {{\pi \cdot L}\over{E_0 \cos{\theta}}}$ (0.2)

where $ L$ is the radiance, $ E_0$ is the extraterrestrial flux, and $ \theta$ is the solar zenith angle. Obviously, reflectivities do not depend on Sun-Earth distance. Please note the difference to transmittance.





Arve Kylling 2010-03-10