==== Case E1: Rayleigh scattering, US standard atmosphere ====

In this case we include the US standard atmosphere, the corresponding Rayleigh scattering optical thickness profile is provided for 450nm. 

//Setup://

  * model atmosphere US-standard, scattering optical thickness provided in file {{:intercomparisons:phase_e:tau_rayleigh_450nm_usstd.dat|}}. The file includes 2 columns where the first is the altitude of the layer boundaries in km, and the second is the layer optical thickness (e.g. the value for 0 km corresponds to the optical thickness for the layer from 0 to 1 km).  
  * wavelength: 450 nm 
  * no molecular absorption
  * Rayleigh depolarization factor: 0.03
  * surface albedo: 0
  
  * Earth radius: 6371 km
  * Height of atmosphere: 120 km

  * Sun-observer geometries as defined in general settings:
      * //viewing zenith angles// (deg): [0, 9, 18, 26, 34, 41, 48, 54, 60, 65, 70, 74, 78, 81, 84, 86, 88, 89, 90] (up-looking at bottom of atmosphere, down-looking at top of atmosphere]
      * //viewing azimuth angles// (deg): 0-180, 10° increment 
      * //solar zenith angles// (deg): [30, 60, 80, 87, 90, 93, 96, 99]
      * //solar azimuth angle// (deg): 0
      * //sensor altitude// (km): 0, 120