Friday, 7 February 2014

ATMOSPHERIC OPTICS - Glory

A Glory is somewhat like a rainbow seen from above - 


usually from an aircraft - and it also involves water droplets that scatter light. Unlike a rainbow, it's not arched, but perfectly circular, and can have several concentric rainbows centred on the antisolar point. Its diameter and number of rings are a function of the size and distribution of water droplets in the clouds below.

Glory on distant stratus - aircraft shadow not visible


The particularity of this optical phenomenon is that the Glory is centred on the shadow of the observer, allowing for a spectacular colourful aura around it (also allowing for many misguided mystical interpretations, no doubt). Flying is not a condition for seeing Glories, as high altitude hikers can encounter blankets of mist below them, which would behave like clouds do, and scatter light to form Glories. They are then called "Brocken spectres". 

The rings maintain their apparent size

Aircraft shadow becomes larger as we approach the stratus for landing

Short movie of the landing:




Conventional diffraction theory cannot explain Glories. Mie theory, which takes into account surface waves, solves some problems but still fails to fully explain the phenomenon.

The water droplets determine the size and number of rings - they varied greatly with the clouds:

Glory - very uneven distribution and size in droplets



Very pretty Glory on thin clouds

Glory over Prague


Log spiral Glory