|Green Flash from the Bohemian Forest, Austria. Observed by Karl Kaiser (Astronomy, biology & meteorology site) on the evening of Jan 10, '09.. ©Karl Kaiser,
shown with permission.
The recent cold weather (see hoar frost crystals) and widespread temperature inversion produced moonset mirages and this miraged sunset with accompanying green flash. There is even a suspicion of a more rare blue flash. The inversion, cold air beneath warmer, has refracted the setting sun's rays to give a 'mock-mirage' where, characteristically, the sun is split into pancake shapes with green flashes in the uppermost layer.
The more traditional green flash is seen as the last sliver of disk slips beneath the horizon and is produced by the opposite arrangement of air - warm beneath cooler.
"These images of the setting sun seem to be unsharp - that is as it was. The air on that day was very "restless", the scintillation of the air was very strong. But I think this is reason why the green colour is seen so well, the green parts are extended. It was not possible to see the upper parts of nearby hills distinctly because of the strong scintillation!"