Atmospheric
Optics
Cloudbow, Glory & Contrail Shadow
Captured by Steve Mattan (Recycledphotons) between Philadelphia, PA and Bozeman, MT.
At left the aircraft's contrail shadow points to an oddly distorted glory. At right there is a bright cloudbow or even a cloud contrast bow. The bow shows faint reds on its outer border and inner supernumerary fringes.
Images ©Steve Mattan
Supernumeraries
The colour subtraction enhancement at far right hints at three supernumeraries. Cloudbow and fogbow supernumeraries are more highly coloured - as here - than the main bow.
Distorted Glory
Nothing to do with the shapes of the cloud tops or distances of the droplets making it.
Everything to do with variations in droplet size across the clouds. Smaller droplets make larger glories.
The glory and cloudbow are all part of the same diffraction pattern produced by sunlight scattering by small droplets at the cloud tops.
The cloudbow, small droplet cousin of the much larger raindrop rainbow, results from a single reflection of light waves in a droplet.
The glory is more complex. waves are internally reflected 5, 6 and even 10 times. Plus, the waves have to travel part of their journey along the drop surface.
Cloud Contrast Bow?
The contrast between the clouds appears greater in the cloudbow.
If real, it arises because rays from the cloud tops are scattered by a single droplet and generate the cloudbow. Sun rays entering hollows between the clouds can be scattered several times and then do not give a bright cloudbow. The hollows are as dark as elsewhere but the cloud tops shine brighter with cloudbow light.
