Contributions to absorption line weakening in the Earth's atmosphere

Daytime skylight is an imperfect representation of the solar spectrum. Scattering of light in the Earth’s atmosphere changes the depths of solar absorption lines. This scattering is due to either molecules or dust grains in the Earth’s atmosphere. Addi- tionally, ground-albedo, the reflection of sunlight from the Earth’s surface back into the atmosphere, may play an important role in diluting the strength of absorption lines. The relative importance of each process is not understood – some studies suggest that ground-albedo is not important, while others indicate that it is significant. We exam- ine the filling-in of absorption lines as a function of angular separation from the Sun, replicating previous measurements with a much richer dataset; because we have line data for the Sun’s entire optical spectrum, we more clearly determine what processes are important.