For the Added Value paper of Bjorn Stevens I did a 1D and a 3D simulation with MYSTIC for an ICON HDCP2 simulation output field. The scene is from 20140729T120230Z, i.e. file 3d_fine_day_DOM03_ML_20140729T120230Z at 156m horizontal resolution.

This day starts with precipitation in the morning followed by small thunderstorms that evolve during the day. By late afternoon they appear mostly in the south of Germany, some of them having turned to severe storms with very heavy precipitation.

The liquid and ice water path at noon is depicted in the following two plots:

The following panel shows the results of the simulations with MYSTIC for solar upward irradiance @ 15km height (model top):

• once with a 1D MonteCarlo simulations (Independent Column Approximation, ICA)
• once with 3D radiative transfer
• then the difference of the two
• and finally a version where the differences are spatially averaged

The solar zenith angle is kept constant at \(\theta = 60^\circ\), aswell as the surface albedo with \(A_g = .2\).

The domain averaged mean difference (bias) of the 1D approximation underestimates the net-reflected sunlight by \(17.5 \ W / m^2\), i.e. a relative bias of 6.4 %.