Bizarre Star - imaged from Alexandria, Egypt by Aymen Ibrahem (Night Sky over Egypt) of the Bibliotheca Alexandrina. ©Aymen Ibrahem, shown with permission.

Hanging as a huge lamp over the Eastern Mediterranean the setting sun is distorted and colour banded.

Temperature inversion layers – abnormally cooler air beneath warmer - are responsible. Efficient vertical mixing requires convection and this in turn requires buoyant warm air free to rise into cooler layers. Inversions inhibit convection and old air with its dust and aerosols is trapped beneath them. We see the result as bands dimming the sun’s light. In addition to being dimmed, rays are refracted by the temperature and atmospheric density gradients to produce mirage distortions.

Strong atmospheric layering of this type can produce ‘mock-miragegreen flashes, at top there is already a hint of green.


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