Mid-level clouds depict in pink colours in the Night Microphysics RGB images.
The BTD (IR12.0 - IR10.8) responsible for the red colour beam is near zero on a scale reaching from -4 (dark) to +2 degrees (intensive red). Hence, the red colour contribution has an average value.
The green colour beam is of varying intensity depending on the thickness and the hight of the low cloud layer. The higher the cloud layer, the smaller the BTD (IR10.8 - IR3.9) and herewith the green contribution.
The blue colour beam is contributing with an average value. The warmer the low cloud is, the more the radiation from IR10.8 is contributing to the blue colour intensity and vice versa.
The pink colour results from a dominating red colour contribution mixed with average blue and a little green in case of mid-level cloudiness (see image below).
Night Microphysics RGB from 29 August 2015, 00:00 UTC
Explanation of the pink colour of mid-level clouds in the Night Microphysics RGB (see the recipe):
• In case of mid-level clouds, the red colour beam dominates slightly over the green and blue colour beam.